A NIRS–fMRI investigation of prefrontal cortex activity during a working memory task

Cognitive and emotional engagement in negotiation: insights from EEG and fNIRS Hyperscanning

In negotiation, individuals collaborate to achieve a shared goal and reach a mutual agreement by understanding their partner's intentions and adapting to them. Unlike most social cognition studies that investigate brain activity in individuals separately, this study employed an innovative hyperscanning approach, which is able to explore the inter-brain synchronization during negotiation. 26 students, divided into 13 dyads, participated in a negotiation decision-making task, requiring convergence on a shared course of action. The interaction was segmented offline into three phases: opener (sharing of individual opinions), central (negotiation), and final phase (shared decision). Electrophysiological (EEG delta, theta, alpha, beta and gamma bands) and hemodynamic (oxygenated-OHb and deoxygenated-HHb hemoglobin) data were collected. Higher HHb levels were observed during the central phase compared to the final phase, suggesting a relative decrease in frontal activation, potentially due to a shift in cognitive processing toward temporoparietal regions, as indicated by EEG findings. Increased delta, theta, and alpha activity was reported in the frontal area, suggesting the engagement of emotional and motivational systems as well as cortical resources for information processing. Finally, beta and gamma bands showed higher activity in the temporo-central and parieto-occipital areas, indicating the activation of perspective-taking. This study highlights how hyperscanning reveals the neural mechanisms of negotiation, where emotional, cognitive, and perspective-taking processes converge.

Predicting whole-brain neural dynamics from prefrontal cortex functional near-infrared spectroscopy signal during movie-watching

Functional near-infrared spectroscopy (fNIRS) offers a portable, cost-effective alternative to functional magnetic resonance imaging (fMRI) for noninvasively measuring neural activity. However, fNIRS measurements are limited to cortical regions near the scalp, missing important medial and deeper brain areas. We introduce a predictive model that maps prefrontal fNIRS signals to whole-brain fMRI activity during movie-watching. By aligning neural responses to a common audiovisual stimulus, our approach leverages shared dynamics across imaging modalities to map fNIRS signals to broader neural activity patterns. We scanned participants with fNIRS and utilized a publicly available fMRI dataset of participants watching the same TV episode. The model was trained on the first half of the episode and tested on a held-out participant watching the second half to assess cross-individual and cross-stimulus generalizability. The model significantly predicted fMRI time courses in 66 out of 122 brain regions, including areas otherwise inaccessible to fNIRS. It also replicated intersubject functional connectivity patterns and retained semantic information about the movie content. The model generalized to an independent dataset from a different TV series, suggesting it captures robust cross-modal mappings across stimuli. Our publicly available models enable researchers to infer broader neural dynamics from localized fNIRS data during naturalistic tasks.

A Randomized Placebo-Controlled Clinical Trial Exploring the Short-Term Cognitive and Cerebrovascular Effects of Consuming Peppermint Tea: A Mediation Study

The cognitive-enhancing effects of peppermint have been widely reported. Vasodilation, causing an increase in cerebral blood flow (CBF) in the prefrontal cortex, has been implicated as a possible mediator. We tested this here. A total of N = 25 individuals, all aged over 18 years, were recruited via convenience sampling. A randomized, single blind placebo-controlled, independent groups design was used to assess whether groups (peppermint vs. placebo control) could be differentiated with respect to change in cognition, assessed via a computerized battery, and change in cerebral blood flow, assessed with Near-Infrared-Spectroscopy (NIRS), from pre-post intervention. Groups disparities in both cognitive and cerebrovascular change scores (from pre-post intervention) emerged. Improvements in cognitive performance were better in the peppermint group. Increases in hemodynamic activity, indexed by Oxygenated (Oxy-Hb) and Total hemoglobin (Total-Hb), were also greater in the peppermint group. Cerebrovascular changes from pre-to post-intervention were unrelated to cognitive changes over the same period, ruling out mediation effects. In conclusion, 200 mL of peppermint, consumed as tea, effectively boosted cognition and cerebral blood flow in otherwise healthy adults. Increased cerebral blood flow, however, did not mediate the cognitive-enhancing effects of peppermint. Future research incorporating larger samples and exploring other neurophysiological mediators is encouraged.

Synthesizing intelligible utterances from EEG of imagined speech

Decoding natural language directly from neural activity is of great interest to people with limited communication means. Being a non-invasive and convenient approach, the electroencephalogram (EEG) offers better portability and wider application potentiality. We present an EEG-to-speech system (ETS) that synthesizes audible, and highly understandable language by EEG of imagined speech. Our ETS applies a specially designed X-shape deep neural network (DNN) to realize an End-to-End correspondence between imagined speech EEG and the speech. The system innovatively incorporates dynamic time warping into the network's training process, using actual speech EEG data as a bridge to temporally align imagined speech EEG signals with speech signals. The ETS performance was evaluated on 13 participants who pretraining four Chinese disyllabic words. These words cover all four tones and 40% of the phonemes in Chinese. Our synthesized utterances' average accuracy across all subjects was 91.23%, the average MOS value was 3.50, and the best accuracy was 99% with an MOS value of 3.99. Furthermore, a partial feedback mechanism for DNN and spectral subtraction-based speech enhancement are introduced to improve the quality of generated speech. Our findings prove that non-invasive approaches can be a significant step in regaining verbal language ability.

The Functional Signature of Decision Making Across Dyads During a Persuasive Scenario: Hemodynamic fNIRS Coherence Measure

INTRODUCTION

Within a shared decision-making process, persuasion dynamics develop as a communication sub-process that can be characterized by different phases. This study examines hemodynamic functional Near-Infrared Spectroscopy (fNIRS) coherence measures in dyads of decision-makers. The interaction occurs in two phases: Phase 1, where the persuader (Pr) introduces the decision topic and uses persuasive strategies, and Phase 2, where the Persuaded (Pd) responds and may agree with the Pr's selected option.

METHOD

Fourteen dyads participated, with fNIRS measuring oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentration changes in the prefrontal cortex (PFC) during both phases. Hemodynamic coherence within dyads was explored through the computation of a dissimilarity index (Euclidean distance).

RESULTS

Phase 2 showed increased HHb dissimilarity, indicating greater divergence in brain activity during the Pd's response phase.

DISCUSSION

These findings suggest that, during persuasion, when Pd responds, there is increased dissimilarity in cognitive and neural processes, without implying a loss of synergy. The study highlights the importance of interactional dynamics in shaping decision outcomes and underscores the potential of fNIRS as a non-invasive tool for monitoring brain activity in clinical and collaborative settings.

Applications and advances of combined fMRI-fNIRs techniques in brain functional research

Understanding the intricate functions of the human brain requires multimodal approaches that integrate complementary neuroimaging techniques. This review systematically examines the integration of functional magnetic resonance imaging (fMRI) and functional near-infrared spectroscopy (fNIRs) in brain functional research, addressing their synergistic potential, methodological advancements, clinical and neuroscientific applications, and persistent challenges. We conducted a comprehensive literature review of 63 studies (from PubMed and Web of Science up to September 2024) using keyword combinations such as fMRI, fNIRs, and multimodal imaging. Our analysis reveals three key findings: (1) Methodological Synergy: Combining fMRI's high spatial resolution with fNIRs's superior temporal resolution and portability enables robust spatiotemporal mapping of neural activity, validated across motor, cognitive, and clinical tasks. Additionally, this study examines experimental paradigms and data processing techniques essential for effective multimodal neuroimaging. (2) Applications: The review categorizes integration methodologies into synchronous and asynchronous detection modes, highlighting their respective applications in spatial localization, validation of efficacy, and mechanism discovery. Synchronous and asynchronous integration modes have advanced research in neurological disorders (e.g., stroke, Alzheimer's), social cognition, and neuroplasticity, while novel hyperscanning paradigms extend applications to naturalistic, interactive settings. (3) Challenges: Hardware incompatibilities (e.g., electromagnetic interference in MRI environments), experimental limitations (e.g., restricted motion paradigms), and data fusion complexities hinder widespread adoption. The future direction emphasizes hardware innovation (such as fNIR probe compatible with MRI), standardized protocol and data integration driven by machine learning, etc. to solve the depth limitation of fNIR and infer subcortical activities. This synthesis underscores the transformative potential of fMRI-fNIRs integration in bridging spatial and temporal gaps in neuroimaging, while enhancing diagnostic and therapeutic strategies and paving the way for future innovations in brain research.

Capturing shared fNIRS responses to visual affective stimuli in young healthy women

Functional near-infrared spectroscopy (fNIRS) studies focusing on prefrontal cortex (PFC) have shown mixed results in relating hemodynamic changes to emotional processing, posing a challenge for clinical practice. Concerns related to instrumentation, recruited sample, task design, signal processing, and data analysis have been highlighted. To minimize some biasing factors, we proposed an experimental approach based on: (1) a homogeneous recruited sample, (2) an identical sequence of content-grouped affective pictures for emotion induction, (3) multi-distance forehead fNIRS recordings to separate cerebral from extra-cerebral components, and (4) a model-free frequency-based analysis to capture shared response patterns across individuals. We piloted a study to assess the feasibility of the approach in a sample of 20 young healthy women during an emotional task with affective pictures of neutral, sexual and violence content. We found coherent fNIRS responses to sexual and violence content located in slow fluctuations (0-0.019 Hz), characterized by positive and negative oxygenation patterns of extra-cerebral and cerebral origin, respectively. Additionally, we corroborated the strong interference of surface hemodynamics. This study proves the feasibility of our approach to identify frequency-specific fNIRS response patterns to affective visual stimuli, which holds promise for exploring functional biomarkers of healthy and altered emotional processing.

Peripheral-central correlation study of acupuncture for chronic tinnitus study protocol for a randomized controlled trial

Purpose

(1) Exploring the evaluation and correlation of peripheral central auditory function in patients with chronic tinnitus. (2) Evaluation of the cumulative effect of acupuncture on peripheral central auditory function in patients with chronic tinnitus.

Method

Our research is structured as a regulated and randomized trial with assessor blinding. Seventy-two participants who qualify with chronic tinnitus will be allocated in a 1:1 ratio to either the acupuncture group or the sham acupuncture group. Additionally, we will recruit 15 healthy individuals as subjects for data collection to observe the correlation of peripheral-central auditory function under different physiological states.

Result

Clinical result metrics encompass the Tinnitus Handicap Inventory (THI), ABR testing, and fNIRS data collection. Evaluations will be carried out at baseline, after 10 treatment sessions.

Conclusion

This research are anticipated to improve our comprehension of the effectiveness and fundamental processes of acupuncture in addressing persistent tinnitus and deeply explain the mechanism of action of the acupuncture method on chronic tinnitus.

Clinical trial registration

ClinicalTrials.gov, identifier NCT06401993.

Near-infrared spectroscopy-guided personalized repetitive transcranial magnetic stimulation for bipolar depression: a case report

Introduction

Transcranial magnetic stimulation (TMS) is a common treatment for depression, particularly in patients unresponsive to conventional therapies. High-frequency (10 Hz), low-frequency (1 Hz), or bilateral (left, high-frequency; right, low-frequency) stimulation of the dorsolateral prefrontal cortex (DLPFC) has been demonstrated to be effective in studies based on prefrontal asymmetry theory, which suggests that depression is associated with reduced left frontal function and increased right frontal function. However, few reliable predictors or biomarkers are available for personalizing treatment protocols on the basis of a patient's brain function. Near-infrared spectroscopy (NIRS), a noninvasive neuroimaging tool that assesses functional changes in the brain during cognitive tasks, can measure a patient's bilateral frontal lobe function in real time. Thus, this tool can aid the development of personalized TMS protocols for patients with depression.

Methods

A 19-year-old woman presented to our psychiatric clinic with bipolar depression. NIRS was performed to select an appropriate TMS protocol for the patient. A verbal fluency test revealed bilateral low frontal lobe function. Thus, we selected a TMS protocol involving 10 sessions of bilateral high-frequency stimulation over 4 days, with each session delivering 3000 pulses on each side of the DLPFC.

Results

Before treatment, the patient's scores on the Hamilton Depression Rating Scale (HAMD), Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), and Young Mania Rating Scale were 40, 57, 40, and 6, respectively. After treatment, her depressive symptoms substantially improved, with HAMD, BDI, and BAI scores decreasing to 17, 21, and 14, respectively. Although the treatment led to side effects such as dizziness and headache, these effects resolved after the treatment. At the 6-month follow-up, the patient's condition was still stable, with HAMD, BDI, and BAI scores of 10, 13, and 7, respectively.

Conclusion

Our case suggests that NIRS can guide the selection of appropriate TMS protocols for patients with bipolar depression. Although our findings are promising, further randomized controlled trials are needed to validate the efficacy and safety of and determine the optimal parameters for this approach.

Reduced prefrontal hemodynamic responses measured using near-infrared spectroscopy in adults with autism spectrum disorder

Aim

Functional neuroimaging studies have suggested that prefrontal cortex dysfunction occurs in individuals with autism spectrum disorder (ASD). Near-infrared spectroscopy (NIRS) is a noninvasive optical tool used to investigate oxygenation and hemodynamic responses in the cerebral cortex by measuring changes in oxygenated hemoglobin. Previous studies using NIRS have suggested that male children with ASD exhibit reduced hemodynamic responses in the dorsolateral prefrontal cortex; however, only a few studies examined this response in adults with ASD.

Methods

We examined the characteristics of prefrontal hemodynamic responses in 114 adults with ASD and 84 typically developing controls. Relative concentrations of oxygenated hemoglobin were measured with frontal probes every 0.1 s during the Stroop color-word task, using 24-channel NIRS.

Results

Our findings demonstrated that the oxygenated hemoglobin changes in the ASD group were significantly smaller than those in the control group at channels 19, 20, 23, and 24- located over the orbitofrontal cortex and frontal pole (p <0.05 for all three channels). The differences in oxygenated hemoglobin changes at Ch 20 were significantly correlated with the Autism-Spectrum Quotient Japanese version (AQ-J) total score and attention switching score, which is a symptom cluster of AQ-J (p = 0.043 and p = 0.009, respectively).

Conclusion

Adults with ASD have reduced prefrontal hemodynamic responses as measured using near-infrared spectroscopy and the reduced activity of the frontal pole in particular is related to reduced attentional function.

Disentangling inhibition toward food and non-food stimuli across two hunger levels: An fNIRS study

While individuals tend to display poorer inhibitory control toward food-related than neutral stimuli, it is unclear whether this challenge is specific to food or extends to other pleasant stimuli. Uncertainty also remains regarding the general impact of hunger on inhibition. To address these questions, we used a within-subjects design whereby 44 healthy adults completed two go/no-go tasks including no-go images of highly palatable foods and no-go images of animals matched for valence and physical properties. Both tasks were completed one week apart in either a fed or a fasted state. Prefrontal cortex activity was measured using functional near-infrared spectroscopy. Poorer behavioral inhibition was observed when participants needed to withhold their response to images of food compared to animals, regardless of hunger state. In addition, more commission errors were made in the fasted compared to the fed condition, regardless of the type of image to avoid responding to. Responses to go trials were slower when these trials were interspersed with food compared to animal no-go trials. However, hunger did not influence go response time. Greater activation was observed in the dorsolateral prefrontal cortex during blocks of trials with (vs. without) no-go images, but brain activity did not differ according to the type of no-go image. The effect of hunger on prefrontal brain activity was also not significant. Exploratory correlations showed that food-related inhibition deficits were positively related to self-reported impulsivity, but unrelated to body mass index. This study suggests that even among healthy adults, food-related inhibitory control may have a unique behavioral signature beyond general inhibition toward pleasant stimuli. Hunger also exerts an independent influence on general inhibitory capabilities, highlighting the importance of carefully controlling hunger levels in inhibition studies.

Diminished negative emotion regulation through affect labeling and reappraisal: insights from functional near infrared spectroscopy on lateral prefrontal cortex activation

BACKGROUND

Reappraisal, an emotion regulation strategy, includes reinterpretation and affect labeling involving verbalizing emotions. In general, reappraisal is supported by lateral prefrontal cortical regions, which are also known to underlie cognitive regulation. Other research has shown that affect labeling combined with reappraisal of negative emotions increases lateral prefrontal cortex activity more than reappraisal alone does, suggesting that affect labeling facilitates emotional regulation. However, the influence of affect labeling on the efficacy of reappraisal in reducing subjective negative emotions has not been determined.

METHODS

In the experiment, 35 participants (mean age = 28.2 years (SD = 9.63); 12 women and 23 men) viewed vignettes that aroused negative emotion. Then, they rated subjective negative emotions as baseline values. Following the baseline rating, the task branched into four conditions, combining affect labeling and emotion regulation factors. In the affect-labeling factor, participants selected emotional labels consistent with their own emotions or not. Regarding the emotion regulation factor, participants engaged in reappraisal to regulate their negative emotions. Throughout the experiment, the intensity of negative emotions was measured three times, mirroring the baseline measurement. Oxyhemoglobin (OxyHb) signal values in prefrontal cortex regions during tasks were measured by functional near-infrared spectroscopy.

RESULTS

Differences between the subjective negative emotion ratings at baseline and after reappraisal indicated that reappraisal significantly reduced negative emotion with and without affect labeling (t (1173.05) = 29.97, p < 0.001), and the combination of affect labeling and reappraisal was less effective in regulating negative emotions at the subjective level than reappraisal without affect labeling (t (1172.03) = 3.15, p < 0.01). Additionally, there was an increase in OxyHb signal in the bilateral dorsolateral prefrontal and right ventral prefrontal cortices while participants performed reappraisal with affect labeling.

CONCLUSION

Our findings suggest that affect labeling, when performed prior to cognitive reappraisal, may influence the process of negative emotion regulation in complex ways. The interaction between affect labeling and reappraisal appears to modulate prefrontal cortex activity, potentially reflecting changes in cognitive processing during emotion regulation attempts. These results highlight the need for further investigation into the intricate relationship between different emotion regulation strategies.

Cognitive Function of Climbers: An Exploratory Study of Working Memory and Climbing Performance

Sport climbing requires a combination of physical and cognitive skills, with working memory (WM) playing a crucial role in performance. This study aimed to investigate the association between WM capacity and climbing ability, while considering potential confounding factors including sex, age, education level, and climbing experience. Additionally, the study compared prefrontal cortex (PFC) hemodynamic responses among different climbing ability groups and sex during WM performance. Twenty-eight climbers participated, with WM assessed using the eCorsi task and PFC hemodynamic responses measured with near infrared spectroscopy (NIRS). Initial linear regression analyses revealed no association between WM and climbing ability. However, significant associations were found after adjustment for covariates. Specifically, sex (p = .014), sex in conjunction with age (p = .026), sex combined with climbing experience (p = .022), and sex along with education level (p = .038) were identified as significant predictors of differences in WM between Expert and Elite climbers. Additionally, notable differences in PFC hemodynamic responses were observed between Expert and Elite climbers, as well as between sexes during the WM task, providing support for differences in WM capacity. This study contributes to understanding the complex relationship between WM capacity and climbing performance, emphasizing the need to account for influencing factors in assessments.

Structural and functional abnormalities across clinical stages of psychosis: A multimodal neuroimaging investigation

BACKGROUND

Structural and functional neurobiological abnormalities have been observed in schizophrenia. Previous studies have concentrated on specific illness stages, obscuring relationships between functional/structural changes and disorder progression. The present study aimed to quantify structural and functional abnormalities across different clinical stages using functional near-infrared spectroscopy (fNIRS) and structural magnetic resonance imaging (sMRI).

METHODS

Fifty-four participants with first-episode schizophrenia (FES), 120 with clinically high risk of psychosis (CHR), and 111 healthy controls (HCs) underwent functional near-infrared spectroscopy (fNIRS) to measure oxyhemoglobin (Oxy-Hb) during the verbal fluency task. Among them, 28FES, 64CHR and 55HC also finished sMRI. Oxy-Hb and gray matter volume (GMV) were compared among the three groups while controlling for covariates, including age, sex, years of education, and task performance. Mediation analysis was utilized to determine the mediating effect of GMV on Oxy-Hb and cognition.

RESULTS

Compared with the HC group, CHR and FES groups showed significantly reduced brain activity. However, there were no significant differences between the FES and CHR. Pronounced GMV increase in the right frontal pole area (F = 4.234, p = 0.016) was identified in the CHR and FES groups. Mediation analysis showed a significant mediation effect of the right frontal pole GMV between Channel 31 Oxy-Hb and processing speed (z = 2.105, p = 0.035) and attention/vigilance (z = 1.992, p = 0.046).

CONCLUSIONS

Brain activation and anatomical deficits were observed in different brain regions, suggesting that anatomical and functional abnormalities are dissociated in the early stages of psychosis. The relationship between neural activity and anatomy may reflect a specific pathophysiology related to cognitive deterioration in schizophrenia.

Anxiety symptoms without depression are associated with cognitive control network (CNN) dysfunction: An fNIRS study

Anxiety is a common psychological disorder associated with other mental disorders, with depression being the most common comorbidity. Few studies have examined the neural mechanisms underlying anxiety after controlling for depression. This study aimed to explore whether there are differences in cortical activation in anxiety patients with different severities whose depression are normal. In the current study, depression levels were normal for 366 subjects-139 healthy subjects, 117 with mild anxiety, and 110 with major anxiety. Using the Hospital Anxiety and Depression Scale (HADS) and a verbal fluency task (VFT) to test subjects' anxiety and depression and cognitive function, respectively. A 53-channel guided near-infrared spectroscopic imaging technology (fNIRS) detected the concentration of oxyhemoglobin (oxy-Hb). Correlation analysis between anxiety severity and oxy-Hb concentration in the brain cortex was performed, as well as ANOVA analysis of oxy-Hb concentration among the three anxiety severity groups. The results showed that anxiety severity was significantly and negatively correlated with oxy-Hb concentrations in the left frontal eye field (lFEF) and in the right dorsolateral prefrontal area (rDLPFC). The oxy-Hb concentration in the lFEF and the rDLPFC were significantly lower in the major anxiety disorder group than that in the control group. This suggests that decreased cortical activity of the lFEF and rDLPFC may be neural markers of anxiety symptoms after controlling for depression. Anxiety symptoms without depression may be result from the dysfunction of the cognitive control network (CCN) which includes the lFEF and rDLPFC.

Impact of ASL Exposure on Spoken Phonemic Discrimination in Adult CI Users: A Functional Near-Infrared Spectroscopy Study

We examined the impact of exposure to a signed language (American Sign Language, or ASL) at different ages on the neural systems that support spoken language phonemic discrimination in deaf individuals with cochlear implants (CIs). Deaf CI users (N = 18, age = 18-24 yrs) who were exposed to a signed language at different ages and hearing individuals (N = 18, age = 18-21 yrs) completed a phonemic discrimination task in a spoken native (English) and non-native (Hindi) language while undergoing functional near-infrared spectroscopy neuroimaging. Behaviorally, deaf CI users who received a CI early versus later in life showed better English phonemic discrimination, albeit phonemic discrimination was poor relative to hearing individuals. Importantly, the age of exposure to ASL was not related to phonemic discrimination. Neurally, early-life language exposure, irrespective of modality, was associated with greater neural activation of left-hemisphere language areas critically involved in phonological processing during the phonemic discrimination task in deaf CI users. In particular, early exposure to ASL was associated with increased activation in the left hemisphere's classic language regions for native versus non-native language phonemic contrasts for deaf CI users who received a CI later in life. For deaf CI users who received a CI early in life, the age of exposure to ASL was not related to neural activation during phonemic discrimination. Together, the findings suggest that early signed language exposure does not negatively impact spoken language processing in deaf CI users, but may instead potentially offset the negative effects of language deprivation that deaf children without any signed language exposure experience prior to implantation. This empirical evidence aligns with and lends support to recent perspectives regarding the impact of ASL exposure in the context of CI usage.

Shared and distinct prefrontal cortex alterations of implicit emotion regulation in depression and anxiety: An fNIRS investigation

BACKGROUND

Emotion regulation deficits, particularly in cognitive reappraisal, are crucial in depression and anxiety. However, research on the neural mechanisms of implicit emotion regulation is lacking, and it remains unclear whether these mechanisms are shared or distinct between the two disorders.

METHODS

We investigated the neural mechanisms of implicit cognitive reappraisal in 28 individuals with major depressive disorder (MDD), 25 with generalized anxiety disorder (GAD), and 30 healthy controls (HC) using functional near-infrared spectroscopy (fNIRS). Participants completed an implicit cognitive reappraisal task and underwent neuropsychological and clinical assessments.

RESULTS

We found that MDD patients reported higher levels of rumination and lower utilization of cognitive reappraisal, while GAD patients reported reduced use of perspective-taking. Notably, both MDD and GAD patients exhibited decreased activation in the dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) compared to HC participants during implicit cognitive reappraisal. Specifically, inadequate OFC activation was observed in MDD patients, while GAD patients demonstrated OFC deactivation during the task. Furthermore, DLPFC activation showed a negative correlation with depression severity in MDD patients, while OFC activation was positively correlated with perspective-taking in GAD patients.

LIMITATIONS

fNIRS has limited depth and spatial resolution.

CONCLUSION

Our fNIRS study is the first to reveal shared and distinct neurobiological profiles of depression and anxiety in implicit emotion regulation. These findings underscore the significance of reduced DLPFC/OFC activation in emotion regulation impairment and highlight unique OFC activation patterns in these disorders. These insights have potential implications for developing cognitive-behavioral therapy and transcranial magnetic stimulation as treatment approaches.

Cross-cultural differences in prefrontal cortex activity in moral judgment: A functional near-infrared spectroscopy (fNIRS) study based on the CNI model

BACKGROUND

In the past, comparative cultural neurological studies of moral judgments have mainly focused on Eastern and Western groups. We initially examined Japanese and Chinese groups, both East Asian cultures. We utilized a recently proposed polynomial model known as the "consequences, norms, and generalized inaction" (CNI) model to investigate the variations in the overall prefrontal cortex activity between these two groups during moral judgment.

METHODS

We employed functional near-infrared spectroscopy (fNIRS) to analyze the prefrontal cortex (PFC) activity within a CNI model of moral judgment among 23 healthy Japanese and 26 healthy Chinese adults.

RESULTS AND CONCLUSIONS

Our study revealed significant differences in the PFC activation between Japanese and Chinese individuals in the CNI moral judgment task context. Specifically, during the CNI task, Chinese men exhibited higher right dorsolateral prefrontal cortex (R-DLPFC) activity than Chinese women. In contrast, Japanese women showed greater left dorsolateral prefrontal cortex (L-DLPFC) activity than Japanese men. In an international comparison, R-DLPFC activity was higher in Chinese men than in Japanese men. Conversely, the left ventrolateral prefrontal cortex activity was higher in Japanese men compared to Chinese men. Additionally, among women, the right ventromedial prefrontal cortex activity was higher in Japanese women than in Chinese women. In conclusion, our findings support the perspective of cultural psychology and identify cultural and sex differences in PFC activity between Japanese and Chinese individuals.

Evaluating Speaker-Listener Cognitive Effort in Speech Communication Through Brain-to-Brain Synchrony: A Pilot Functional Near-Infrared Spectroscopy Investigation

PURPOSE

We explore a new approach to the study of cognitive effort involved in listening to speech by measuring the brain activity in a listener in relation to the brain activity in a speaker. We hypothesize that the strength of this brain-to-brain synchrony (coupling) reflects the magnitude of cognitive effort involved in verbal communication and includes both listening effort and speaking effort. We investigate whether interbrain synchrony is greater in native-to-native versus native-to-nonnative communication using functional near-infrared spectroscopy (fNIRS).

METHOD

Two speakers participated, a native speaker of American English and a native speaker of Korean who spoke English as a second language. Each speaker was fitted with the fNIRS cap and told short stories. The native English speaker provided the English narratives, and the Korean speaker provided both the nonnative (accented) English and Korean narratives. In separate sessions, fNIRS data were obtained from seven English monolingual participants ages 20-24 years who listened to each speaker's stories. After listening to each story in native and nonnative English, they retold the content, and their transcripts and audio recordings were analyzed for comprehension and discourse fluency, measured in the number of hesitations and articulation rate. No story retellings were obtained for narratives in Korean (an incomprehensible language for English listeners). Utilizing fNIRS technique termed sequential scanning, we quantified the brain-to-brain synchronization in each speaker-listener dyad.

RESULTS

For native-to-native dyads, multiple brain regions associated with various linguistic and executive functions were activated. There was a weaker coupling for native-to-nonnative dyads, and only the brain regions associated with higher order cognitive processes and functions were synchronized. All listeners understood the content of all stories, but they hesitated significantly more when retelling stories told in accented English. The nonnative speaker hesitated significantly more often than the native speaker and had a significantly slower articulation rate. There was no brain-to-brain coupling during listening to Korean, indicating a break in communication when listeners failed to comprehend the speaker.

CONCLUSIONS

We found that effortful speech processing decreased interbrain synchrony and delayed comprehension processes. The obtained brain-based and behavioral patterns are consistent with our proposal that cognitive effort in verbal communication pertains to both the listener and the speaker and that brain-to-brain synchrony can be an indicator of differences in their cumulative communicative effort.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.25452142.

Motor Processing in Children With Cochlear Implants as Assessed by Functional Near-Infrared Spectroscopy

Auditory-motor and visual-motor networks are often coupled in daily activities, such as when listening to music and dancing; but these networks are known to be highly malleable as a function of sensory input. Thus, congenital deafness may modify neural activities within the connections between the motor, auditory, and visual cortices. Here, we investigated whether the cortical responses of children with cochlear implants (CI) to a simple and repetitive motor task would differ from that of children with typical hearing (TH) and we sought to understand whether this response related to their language development. Participants were 75 school-aged children, including 50 with CI (with varying language abilities) and 25 controls with TH. We used functional near-infrared spectroscopy (fNIRS) to record cortical responses over the whole brain, as children squeezed the back triggers of a joystick that vibrated or not with the squeeze. Motor cortex activity was reflected by an increase in oxygenated hemoglobin concentration (HbO) and a decrease in deoxygenated hemoglobin concentration (HbR) in all children, irrespective of their hearing status. Unexpectedly, the visual cortex (supposedly an irrelevant region) was deactivated in this task, particularly for children with CI who had good language skills when compared to those with CI who had language delays. Presence or absence of vibrotactile feedback made no difference in cortical activation. These findings support the potential of fNIRS to examine cognitive functions related to language in children with CI.

Wearable functional near-infrared spectroscopy for measuring dissociable activation dynamics of prefrontal cortex subregions during working memory

The prefrontal cortex (PFC) has been extensively studied in relation to various cognitive abilities, including executive function, attention, and memory. Nevertheless, there is a gap in our scientific knowledge regarding the functionally dissociable neural dynamics across the PFC during a cognitive task and their individual differences in performance. Here, we explored this possibility using a delayed match-to-sample (DMTS) working memory (WM) task using NIRSIT, a high-density, wireless, wearable functional near-infrared spectroscopy (fNIRS) system. First, upon presentation of the sample stimulus, we observed an immediate signal increase in the ventral (orbitofrontal) region of the anterior PFC, followed by activity in the dorsolateral PFC. After the DMTS test stimulus appeared, the orbitofrontal cortex activated once again, while the rest of the PFC showed overall disengagement. Individuals with higher accuracy showed earlier and sustained activation of the PFC across the trial. Furthermore, higher network efficiency and functional connectivity in the PFC were correlated with individual WM performance. Our study sheds new light on the dynamics of PFC subregional activity during a cognitive task and its potential applicability in explaining individual differences in experimental, educational, or clinical populations. PRACTITIONER POINTS: Wearable functional near-infrared spectroscopy (fNIRS) captured dissociable temporal dynamics across prefrontal subregions during a delayed match-to-sample task. Anterior regions of the orbitofrontal cortex (OFC) activated first during the delay period, followed by the dorsolateral prefrontal cortex (PFC). PFC disengaged overall after the delay, but the OFC reactivated to the test stimulus. Earlier and sustained activation of PFC was associated with better accuracy. Functional connectivity and network efficiency also varied with task performance.

A new perspective for evaluating the efficacy of tACS and tDCS in improving executive functions: A combined tES and fNIRS study

BACKGROUND

Executive function enhancement is considered necessary for improving the quality of life of patients with neurological or psychiatric disorders, such as attention-deficit/hyperactivity disorder, obsessive-compulsive disorder and Alzheimer's disease. Transcranial electrical stimulation (tES) has been shown to have some beneficial effects on executive functioning, but the quantification of these improvements remains controversial. We aimed to explore the potential beneficial effects on executive functioning induced by the use of transcranial alternating current stimulation (tACS)/transcranial direct current stimulation (tDCS) on the right inferior frontal gyrus (IFG) and the accompanying brain function variations in the resting state.

METHODS

We recruited 229 healthy adults to participate in Experiments 1 (105 participants) and 2 (124 participants). The participants in each experiment were randomly divided into tACS, tDCS, and sham groups. The participants completed cognitive tasks to assess behavior related to three core components of executive functions. Functional near-infrared spectroscopy (fNIRS) was used to monitor the hemodynamic changes in crucial cortical regions in the resting state.

RESULTS

Inhibition and cognitive flexibility (excluding working memory) were significantly increased after tACS/tDCS, but there were no significant behavioral differences between the tACS and tDCS groups. fNIRS revealed that tDCS induced decreases in the functional connectivity (increased neural efficiency) of the relevant cortices.

CONCLUSIONS

Enhancement of executive function was observed after tES, and the beneficial effects of tACS/tDCS may need to be precisely evaluated via brain imaging indicators at rest. tDCS revealed better neural benefits than tACS during the stimulation phase. These findings might provide new insights for selecting intervention methods in future studies and for evaluating the clinical efficacy of tES.

Validation of a mobile fNIRS device for measuring working memory load in the prefrontal cortex

Functional near-infrared spectroscopy (fNIRS) is a neuroimaging technique that measures cortical blood flow to infer neural activation. Traditionally limited to laboratory settings due to high costs and complex operation, recent advancements have introduced mobile fNIRS devices, significantly broadening the scope of potential research participants. This study validates the use of the Mendi, a two-channel mobile fNIRS system, for measuring prefrontal oxyhemoglobin concentration changes during an n-back task. We manipulated task difficulty through different n-back levels (one-back versus three-back), revealing increased oxyhemoglobin concentrations in the prefrontal cortex during the more demanding three-back task compared to the one-back task. This finding demonstrates the Mendi's ability to distinguish between low and high cognitive task loads. Behavioural data, showing a decrease in accuracy under high load conditions, further corroborates these neuroimaging findings. Our study validates the Mendi mobile fNIRS system as an effective tool for assessing working memory load and underscores its potential in enhancing neuroscientific research accessibility. The user-friendly and cost-effective nature of mobile fNIRS systems like the Mendi opens up neuroscientific research to a diverse set of participants, enabling the investigation of neural processes in real-world environments across a variety of demographic groups.

Artificial Intelligence-Based Diagnostic Support System for Functional Dyspepsia Based on Brain Activity and Food Preference

Background and aim Disorders of gut-brain interaction (DGBI) are disorders where no organic clinical abnormalities are detected such as functional dyspepsia (FD) and irritable bowel syndrome (IBS). The brain activity of individuals with FD and IBS differs from that of healthy controls. Artificial intelligence can distinguish healthy controls from individuals with DGBI using several biomarkers. This study aimed to establish an artificial intelligence-based diagnostic support system using food preferences and brain activity in patients with DGBI. Methods ROME IV criteria were used to diagnose patients with FD and IBS. Their food preference was scored using a visual analog scale, and brain activity in the prefrontal cortex was investigated using functional near-infrared spectroscopy (fNIRS). The diagnostic model was developed based on the brain activity and visual analog scale scores for food using an artificial neural network model. Results Forty-one participants, including 25 patients with DGBI were enrolled in the study. The accuracy of the artificial intelligence-based diagnostic model using an artificial neural network in differentiating between healthy controls and patients with DGBI and between healthy controls and those with FD were 72.3% and 77.1%, respectively. Conclusions The artificial intelligence-based diagnostic model using brain activity and preference to food images showed sufficiently high accuracy in distinguishing patients with DGBI from healthy controls, and those with FD from healthy controls. Therefore, the fNIRS system provides objective evidence for diagnosing DGBI.

Brain activity in response to food images in patients with irritable bowel syndrome and functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) and irritable bowel syndrome (IBS) are caused and exacerbated by consumption of fatty foods. However, no study has evaluated brain activity in response to food images in patients with disorders of gut-brain interaction (DGBI). This study aimed to compare food preference and brain activity when viewing food images between patients with DGBI and healthy controls.

METHODS

FD and IBS were diagnosed using the ROME IV criteria. Food preference was assessed using a visual analog scale (VAS). Brain activity in the prefrontal cortex (PFC) in response to food images was investigated using functional near-infrared spectroscopy (fNIRS).

RESULTS

Forty-one patients were enrolled, including 25 with DGBI. The mean VAS scores for all foods (controls vs. FD vs. IBS: 69.1 ± 3.3 vs. 54.8 ± 3.8 vs. 62.8 ± 3.7, p = 0.02), including fatty foods (78.1 ± 5.4 vs. 43.4 ± 6.3 vs. 64.7 ± 6.1, p < 0.01), were the lowest in patients with FD among all groups. Patients with FD had significantly higher brain activity in the left PFC than those with IBS and healthy controls (mean z-scores in controls vs. FD vs. IBS: - 0.077 ± 0.03 vs. 0.125 ± 0.04 vs. - 0.002 ± 0.03, p < 0.001).

CONCLUSIONS

Patients with DGBI, particularly those with FD, disliked fatty foods. The brain activity in patients with DGBI differed from that in healthy controls. Increased activity in the PFC of patients with FD was confirmed.

NIRS-aided differential diagnosis among patients with major depressive disorder, bipolar disorder, and schizophrenia

BACKGROUND

To establish a clinically applicable neuroimaging-guided diagnostic support system that uses near-infrared spectroscopy (NIRS) for differential diagnosis at the individual level among major depressive disorder (MDD), bipolar disorder (BPD), and schizophrenia (SZ).

METHODS

A total of 192 participants were recruited, including 40 patients with MDD, 38 patients with BPD, 65 patients with SZ, and 49 healthy individuals. We analyzed the spatiotemporal characteristics of hemodynamic responses in the frontotemporal cortex during a verbal fluency test (VFT) measured by NIRS to assess the accuracy of single-subject classification for differential diagnosis among the three psychiatric disorders. The optimal threshold of the frontal centroid value (54 seconds) was utilized on the basis of the findings of the Japanese study.

RESULTS

The application of the optimal threshold of the frontal centroid value (54 seconds) allowed for the accurate differentiation of patients with unipolar MDD (72.5%) from BPD (78.9%) or SZ (84.6%).

CONCLUSION

These results suggest that the NIRS-aided differential diagnosis of major psychiatric disorders can be a promising biomarker in Taiwan. Future multi-site studies are needed to validate our findings.

Brain language networks and cognitive outcomes in children with frontotemporal lobe epilepsy

Introduction

Pediatric frontal and temporal lobe epilepsies (FLE, TLE) have been associated with language impairments and structural and functional brain alterations. However, there is no clear consensus regarding the specific patterns of cerebral reorganization of language networks in these patients. The current study aims at characterizing the cerebral language networks in children with FLE or TLE, and the association between brain network characteristics and cognitive abilities.

Methods

Twenty (20) children with FLE or TLE aged between 6 and 18 years and 29 age- and sex-matched healthy controls underwent a neuropsychological evaluation and a simultaneous functional near-infrared spectroscopy and electroencephalography (fNIRS-EEG) recording at rest and during a receptive language task. EEG was used to identify potential subclinical seizures in patients. We removed these time intervals from the fNIRS signal to investigate language brain networks and not epileptogenic networks. Functional connectivity matrices on fNIRS oxy-hemoglobin concentration changes were computed using cross-correlations between all channels.

Results and discussion

Group comparisons of residual matrices (=individual task-based matrix minus individual resting-state matrix) revealed significantly reduced connectivity within the left and between hemispheres, increased connectivity within the right hemisphere and higher right hemispheric local efficiency for the epilepsy group compared to the control group. The epilepsy group had significantly lower cognitive performance in all domains compared to their healthy peers. Epilepsy patients' local network efficiency in the left hemisphere was negatively associated with the estimated IQ (p = 0.014), suggesting that brain reorganization in response to FLE and TLE does not allow for an optimal cognitive development.

Surface-based integration approach for fNIRS-fMRI reliability assessment

INTRODUCTION

Studies integrating functional near-infrared spectroscopy (fNIRS) with functional MRI (fMRI) employ heterogeneous methods in defining common regions of interest in which similarities are assessed. Therefore, spatial agreement and temporal correlation may not be reproducible across studies. In the present work, we address this issue by proposing a novel method for integration and analysis of fNIRS and fMRI over the cortical surface.

MATERIALS AND METHODS

Eighteen healthy volunteers (age mean±SD 30.55 ± 4.7, 7 males) performed a motor task during non-simultaneous fMRI and fNIRS acquisitions. First, fNIRS and fMRI data were integrated by projecting subject- and group-level source maps over the cortical surface mesh to define anatomically constrained functional ROIs (acfROI). Next, spatial agreement and temporal correlation were quantified as Dice Coefficient (DC) and Pearson's correlation coefficient between fNIRS-fMRI in the acfROIs.

RESULTS

Subject-level results revealed moderate to substantial spatial agreement (DC range 0.43 - 0.64), confirmed at the group-level only for blood oxygenation level-dependent (BOLD) signal vs. HbO2 (0.44 - 0.69), while lack of agreement was found for BOLD vs. HbR in some instances (0.05 - 0.49). Subject-level temporal correlation was moderate to strong (0.79 - 0.85 for BOLD vs. HbO2 and -0.62 to -0.72 for BOLD vs. HbR), while an overall strong correlation was found for group-level results (0.95 - 0.98 for BOLD vs. HbO2 and -0.91 to -0.94 for BOLD vs. HbR).

CONCLUSION

The proposed method directly compares fNIRS and fMRI by projecting individual source maps to the cortical surface. Our results indicate spatial and temporal correspondence between fNIRS and fMRI, and promotes the use of fNIRS when more ecological acquision settings are required, such as longitudinal monitoring of brain activity before and after rehabilitation.

Neural mechanisms of long-term exercise intervention on cognitive performance among short-sleep young adults: A hemodynamic study

OBJECTIVES

Short-sleep is becoming increasingly common and may negatively affect brain function including cognitive ability. Physical exercise has been proved to improve cognitive function while intensity matters. This study was conducted to examine the effects of 12-week exercise interventions on cognitive performance and prefrontal cortex activation related to task performance in short-sleep young adults.

METHODS

A total of 50 subjects (23.62 ± 5.28 years and 24 men) with regular short-sleep conditions (<7 h per night) participated in this study and were divided into three groups: control, moderate-intensity continuous training (MICT), and high-intensity interval training (HIIT) group. As task performance (congruent and incongruent Stroop) was monitored, changes in prefrontal oxygenated hemoglobin (oxyHb), an indicator of cortical activation, were measured using functional near-infrared spectroscopy (fNIRS) to explore the hemodynamics mechanism.

RESULTS

Post 12-week intervention, significant differences in reaction time for congruent [β (95%CI): -0.045 (-0.088, -0.002), p = 0.039] and incongruent Stroop tests [β (95%CI): -0.058 (-0.113, -0.003), p = 0.038] were found only in the MICT intervention group. However, HIIT did not show significant improvements in cognitive function. Left middle frontal gyrus (Frontal Mid L) and right dorsolateral superior frontal gyrus (Frontal Sup R) were both stimulated by MICT and HIIT. Moreover, left dorsolateral superior frontal gyrus (Frontal Sup L) was stimulated by MICT.

CONCLUSION

The findings indicated that 12-week MICT improved cognition by significantly increasing cortical activity across more brain regions. Thus, we suggested that maintaining moderate-intensity exercise could benefit cognitive function despite short sleep.

Prefrontal dysfunction in post-COVID-19 hyposmia: an EEG/fNIRS study

Introduction

Subtle cognitive dysfunction and mental fatigue are frequent after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, characterizing the so-called long COVID-19 syndrome. This study aimed to correlate cognitive, neurophysiological, and olfactory function in a group of subjects who experienced acute SARS-CoV-2 infection with persistent hyposmia at least 12 weeks before the observation.

Methods

For each participant (32 post-COVID-19 patients and 16 controls), electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) data were acquired using an integrated EEG-fNIRS system during the execution of a P300 odd-ball task and a Stroop test. The Sniffin' Sticks test was conducted to assess subjects' olfactory performance. The Montreal Cognitive Assessment (MoCA) and the Frontal Assessment Battery (FAB) were also administered.

Results

The post-COVID-19 group consisted of 32 individuals (20 women and 12 men) with an average education level of 12.9 ± 3.12 years, while the control group consisted of 16 individuals (10 women and 6 men) with an average education level of 14.9 ± 3.2 years. There were no significant differences in gender (X2 = 0, p = 1) or age between the two groups (age 44.81 ± 13.9 vs. 36.62 ± 11.4, p = 0.058). We identified a lower concentration of oxyhemoglobin (p < 0.05) at the prefrontal cortical level in post-COVID-19 subjects during the execution of the Stroop task, as well as a reduction in the amplitude of the P3a response. Moreover, we found that post-COVID-19 subjects performed worst at the MoCA screening test (p = 0.001), Sniffin's Sticks test (p < 0.001), and Stroop task response latency test (p < 0.001).

Conclusions

This study showed that post-COVID-19 patients with persistent hyposmia present mild deficits in prefrontal function, even 4 months after the end of the infection. These deficits, although subtle, could have long-term implications for quality of life and cognitive wellbeing. It is essential to continue monitoring and evaluating these patients to better understand the extent and duration of cognitive impairments associated with long COVID-19.

Associations between frontal lobe activity and depressive symptoms in patients with major depressive disorder receiving rTMS treatment: a near-infrared spectroscopy study

Introduction

The effects of repetitive transcranial magnetic stimulation (rTMS) on the left dorsolateral prefrontal cortex (DLPFC) in patients with major depressive disorder (MDD) have been proved to have antidepressant effects. However, the absence of biomarkers to assess treatment response remains a challenge. This research aims to explore the relationship between frontal lobe activity, measured using near infrared spectroscopy (NIRS), and changes in symptoms among MDD patients following rTMS treatment.

Methods

A total of 26 MDD patients underwent 20 sessions of 10  Hz rTMS targeting the left DLPFC. NIRS was used to measure frontal lobe activity during a verbal fluency test at baseline, after 10 rTMS sessions, and after 20 rTMS sessions. Responders were defined as individuals with more than a 50% reduction in symptoms based on the 21-item Hamilton Depression Rating Scale after 20 rTMS sessions.

Results

Among the 14 responders, an increase in frontal lobe activity was significantly correlated with improvements in depressive symptoms following 10 (p = 0.0001) and 20 rTMS sessions (p = 0.007). Additionally, frontal lobe activity after 10 rTMS sessions was significantly associated with symptom improvement after 20 sessions (p = 0.001). These associations were not observed among non-responders.

Conclusion

The findings from this study indicate distinct patterns of frontal lobe activity between responders and non-responders to rTMS treatment, suggesting that NIRS has the potential to serve as a biomarker for monitoring treatment response in MDD patients undergoing rTMS.

Functional near infrared spectroscopy detects cortical activation changes concurrent with memory loss in postmenopausal women with Type II Diabetes

Older adults with Type II Diabetes Mellitus (DM) experience mild cognitive impairment, specifically in the domain of recall/working memory. No consistent causative structural cortical deficits have been identified in persons with DM (PwDM). Memory deficits may be exacerbated in older adult females, who are at the highest risk of cardiovascular decline due to DM. The focus of the current study was to evaluate functional cortical hemodynamic activity during memory tasks in postmenopausal PwDM. Functional Near Infrared Spectroscopy (fNIRS) was used to monitor oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) during memory-based tasks in a cross-sectional sample of postmenopausal women with DM. Twenty-one community-dwelling DM females (age = 65 ± 6 years) and twenty-one age- and sex-matched healthy controls (age = 66 ± 6 years) were evaluated. Working memory performance (via N-back) was evaluated while study participants donned cortical fNIRS. Health state, metabolic data, and menopausal status data were also collected. Deficits in working memory accuracy were found in the DM group as compared to controls. Differences in HbO responses emerged in the DM group. The DM group exhibited altered PFC activity magnitudes and increased functional cortical activity across ROIs compared to controls. HbO and HbR responses were not associated with worsened health state measures. These data indicate a shift in cortical activity patterns with memory deficits in postmenopausal PwDM. This DM-specific shift of HbO is a novel finding that is unlikely to be detected by fMRI. This underscores the value of using non-MRI-based neuroimaging techniques to evaluate cortical hemodynamic function to detect early mild cognitive impairment.

Functional near-infrared spectroscopy in elderly patients with four types of dementia

BACKGROUND

Functional near-infrared spectroscopy (fNIRS) is commonly used to study human brain function by measuring the hemodynamic signals originating from cortical activation and provides a new noninvasive detection method for identifying dementia.

AIM

To investigate the fNIRS imaging technique and its clinical application in differential diagnosis of subtype dementias including frontotemporal lobe dementia, Lewy body dementia, Parkinson’s disease dementia (PDD) and Alzheimer’s disease (AD).

METHODS

Four patients with different types of dementia were examined with fNIRS during two tasks and a resting state. We adopted the verbal fluency task, working memory task and resting state task. Each patient was compared on the same task. We conducted and analyzed the fNIRS data using a general linear model and Pearson’s correlation analysis.

RESULTS

Compared with other types of dementias, fNIRS showed the left frontotemporal and prefrontal lobes to be poorly activated during the verbal fluency task in frontotemporal dementia. In Lewy body dementia, severe asymmetry of prefrontal lobes appeared during both verbal fluency and working memory tasks, and the patient had low functional connectivity during a resting state. In PDD, the patient’s prefrontal cortex showed lower excitability than the temporal lobe during the verbal fluency task, while the prefrontal cortex showed higher excitability during the working memory task. The patient with AD showed poor prefrontal and temporal activation during the working memory task, and more activation of frontopolar instead of the dorsolateral prefrontal cortex.

CONCLUSION

Different hemodynamic characteristics of four types of dementia (as seen by fNIRS imaging) provides evidence that fNIRS can serve as a potential tool for the diagnosis between dementia subtypes.

The analysis of brain functional connectivity of post-stroke cognitive impairment patients: an fNIRS study

Background

Post-stroke cognitive impairment (PSCI) is a considerable risk factor for developing dementia and reoccurrence of stroke. Understanding the neural mechanisms of cognitive impairment after stroke can facilitate early identification and intervention.

Objectives

Using functional near-infrared spectroscopy (fNRIS), the present study aimed to examine whether resting-state functional connectivity (FC) of brain networks differs in patients with PSCI, patients with Non-PSCI (NPSCI), and healthy controls (HCs), and whether these features could be used for clinical diagnosis of PSCI.

Methods

The present study recruited 16 HCs and 32 post-stroke patients. Based on the diagnostic criteria of PSCI, post-stroke patients were divided to the PSCI or NPSCI group. All participants underwent a 6-min resting-state fNRIS test to measure the hemodynamic responses from regions of interests (ROIs) that were primarily distributed in the prefrontal, somatosensory, and motor cortices.

Results

The results showed that, when compared to the HC group, the PSCI group exhibited significantly decreased interhemispheric FC and intra-right hemispheric FC. ROI analyses showed significantly decreased FC among the regions of somatosensory cortex, dorsolateral prefrontal cortex, and medial prefrontal cortex for the PSCI group than for the HC group. However, no significant difference was found in the FC between the PSCI and the NPSCI groups.

Conclusion

Our findings provide evidence for compromised interhemispheric and intra-right hemispheric functional connectivity in patients with PSCI, suggesting that fNIRS is a promising approach to investigate the effects of stroke on functional connectivity of brain networks.

The Influence of Extracerebral Tissue on Continuous Wave Near-Infrared Spectroscopy in Adults: A Systematic Review of In Vivo Studies

Near-infrared spectroscopy (NIRS) is a non-invasive technique for measuring regional tissue haemoglobin (Hb) concentrations and oxygen saturation (rSO₂). It may be used to monitor cerebral perfusion and oxygenation in patients at risk of cerebral ischemia or hypoxia, for example, during cardiothoracic or carotid surgery. However, extracerebral tissue (mainly scalp and skull tissue) influences NIRS measurements, and the extent of this influence is not clear. Thus, before more widespread use of NIRS as an intraoperative monitoring modality is warranted, this issue needs to be better understood. We therefore conducted a systematic review of published in vivo studies of the influence of extracerebral tissue on NIRS measurements in the adult population. Studies that used reference techniques for the perfusion of the intra- and extracerebral tissues or that selectively altered the intra- or extracerebral perfusion were included. Thirty-four articles met the inclusion criteria and were of sufficient quality. In 14 articles, Hb concentrations were compared directly with measurements from reference techniques, using correlation coefficients. When the intracerebral perfusion was altered, the correlations between Hb concentrations and intracerebral reference technique measurements ranged between |r| = 0.45-0.88. When the extracerebral perfusion was altered, correlations between Hb concentrations and extracerebral reference technique measurements ranged between |r| = 0.22-0.93. In studies without selective perfusion modification, correlations of Hb with intra- and extracerebral reference technique measurements were generally lower (|r| < 0.52). Five articles studied rSO₂. There were varying correlations of rSO₂ with both intra- and extracerebral reference technique measurements (intracerebral: |r| = 0.18-0.77, extracerebral: |r| = 0.13-0.81). Regarding study quality, details on the domains, participant selection and flow and timing were often unclear. We conclude that extracerebral tissue indeed influences NIRS measurements, although the evidence (i.e., correlation) for this influence varies considerably across the assessed studies. These results are strongly affected by the study protocols and analysis techniques used. Studies employing multiple protocols and reference techniques for both intra- and extracerebral tissues are therefore needed. To quantitatively compare NIRS with intra- and extracerebral reference techniques, we recommend applying a complete regression analysis. The current uncertainty regarding the influence of extracerebral tissue remains a hurdle in the clinical implementation of NIRS for intraoperative monitoring. The protocol was pre-registered in PROSPERO (CRD42020199053).

Brain Activation of Unpleasant Emotions Increases Catastrophizing in Patients with Chronic Pain

BACKGROUND

Catastrophic thinking among patients with chronic pain impairs their quality of life and increases anxiety levels. Further, severe pain causes high emotional brain sensitivity and unpleasant feelings. However, the effects of emotional changes on catastrophic thinking in patients with chronic pain remain unclear.

AIMS

We hypothesised that emotional brain activity during mild pain stimuli would affect catastrophic thinking in these patients. We aimed to examine the relationship between unpleasant emotional brain activation and catastrophic thinking due to pain stimuli in patients with chronic pain.

DESIGN

This was a prospective observational study.

PARTICIPANTS

We included patients with chronic pain and healthy individuals.

METHODS

The impact of emotional brain activity on catastrophic thinking was evaluated, specifically, the skin conductance response and oxygenated haemoglobin levels using near-infrared spectroscopy. After receiving three different pain stimuli, the participants were evaluated using the Numeric Rating Scale, Pain Catastrophising Scale, and McGill Pain Questionnaire.

RESULTS

There were 28 patients in the chronic pain group and 33 patients in the healthy group. There was no between-group difference in oxygenated haemoglobin levels during pain stimulation. The chronic pain group showed a higher Pain Catastrophising Scale score and skin conductance response than the healthy group (p < .05). In the chronic pain group, oxygenated haemoglobin levels after pain stimuli were significantly associated with the Pain Catastrophising Scale score and skin conductance response (p < .05).

CONCLUSIONS

Brain activity of unpleasant emotions may influence catastrophic thinking in patients with chronic pain.

Multimodal assessment of the spatial correspondence between fNIRS and fMRI hemodynamic responses in motor tasks

Functional near-infrared spectroscopy (fNIRS) provides a cost-efficient and portable alternative to functional magnetic resonance imaging (fMRI) for assessing cortical activity changes based on hemodynamic signals. The spatial and temporal underpinnings of the fMRI blood-oxygen-level-dependent (BOLD) signal and corresponding fNIRS concentration of oxygenated (HbO), deoxygenated (HbR), and total hemoglobin (HbT) measurements are still not completely clear. We aim to analyze the spatial correspondence between these hemodynamic signals, in motor-network regions. To this end, we acquired asynchronous fMRI and fNIRS recordings from 9 healthy participants while performing motor imagery and execution. Using this multimodal approach, we investigated the ability to identify motor-related activation clusters in fMRI data using subject-specific fNIRS-based cortical signals as predictors of interest. Group-level activation was found in fMRI data modeled from corresponding fNIRS measurements, with significant peak activation found overlapping the individually-defined primary and premotor motor cortices, for all chromophores. No statistically significant differences were observed in multimodal spatial correspondence between HbO, HbR, and HbT, for both tasks. This suggests the possibility of translating neuronal information from fMRI into an fNIRS motor-coverage setup with high spatial correspondence using both oxy and deoxyhemoglobin data, with the inherent benefits of translating fMRI paradigms to fNIRS in cognitive and clinical neuroscience.

A Method for Using Video Presentation to Increase Cortical Region Activity during Motor Imagery Tasks in Stroke Patients

Previous studies have reported that stroke patients have difficulty recalling the motor imagery (MI) of a task, also known as MI vividness. Research on combining MI with action observation is gaining importance as a method to improve MI vividness. We enrolled 10 right-handed stroke patients and compared MI vividness and cortical activity under different presentation methods (no inverted image, inverted image of another individual’s hand, and an inverted image of the patient’s nonparalyzed hand) using near-infrared spectroscopy. Images of the nonparalyzed upper limb were inverted to make the paralyzed upper limb appear as if it were moving. Three tasks (non inverted image, AO + MI (other hand), AO + MI (own hand)) were randomly performed on 10 stroke patients. MI vividness was significantly higher when the inverted image of the nonparalyzed upper limb was presented compared to the other conditions (p < 0.01). The activity of the cortical regions was also significantly enhanced (p < 0.01). Our study highlights the potential application of inverted images of a stroke patient’s own nonparalyzed hand in mental practice to promote the motor recovery of stroke patients. This technique achieved higher levels of MI vividness and cortical activity when performing motor tasks.

Prefrontal cortex activities during verbal fluency and emotional words tasks in major depressive, adjustment, and bipolar disorders with depressive states

BACKGROUND

It can be difficult to differentiate psychiatric disorders from depressive states, with little knowledge on how to differentiate them. This study aimed to evaluate changes in brain activity during cognitive and emotional tasks in patients with depressive state to help with differential diagnoses.

METHODS

Sixty-two patients with depressive states [17 with adjustment disorder (AD), 27 with major depressive disorder (MDD), and 18 with bipolar disorder (BD)] and 34 healthy controls (HC) were recruited. We used a verbal fluency task (VFT) and emotional word tasks with happy and threat words. Functional near-infrared spectroscopy measured the relative change in oxygenated hemoglobin in the frontotemporal areas.

RESULTS

During the VFT, patients with AD or MDD showed significantly reduced activation in the bilateral frontotemporal region (all p < 0.01), whereas patients with BD demonstrated significantly reduced activation in the right frontotemporal areas compared to HC (p < 0.01). During the emotional words task with happy words, patients with MDD showed significantly increased activity in the frontopolar area compared to HC (p = 0.023). Binary logistic regression analysis showed that MDD or BD was significantly associated with brain activity during the happy word task. In distinguishing MDD or BD from HC, the happy words task performed equally well, with an area under the curve of 0.70.

LIMITATIONS

All study patients were taking psychotropic drugs.

CONCLUSIONS

Brain activation in response to a combination of cognitive or emotional stimuli could assist in distinguishing patients with depressive states from healthy controls.

Effects of three-dimension movie visual fatigue on cognitive performance and brain activity

To further develop three-dimensional (3D) applications, it is important to elucidate the negative effects of 3D applications on the human body and mind. Thus, this study investigated differences in the effects of visual fatigue on cognition and brain activity using visual and auditory tasks induced by watching a 1-h movie in two dimensions (2D) and 3D. Eighteen young men participated in this study. Two conditions were randomly performed for each participant on different days, namely, watching the 1-h movie on television in 2D (control condition) and 3D (3D condition). Before and after watching the 1-h movie on television, critical flicker fusion frequency (CFF: an index of visual fatigue), and response accuracy and reaction time for the cognitive tasks were determined. Brain activity during the cognitive tasks was evaluated using a multi-channel near-infrared spectroscopy system. In contrast to the control condition, the decreased CFF, and the lengthened reaction time and the decreased activity around the right primary somatosensory cortex during Go/NoGo blocks in the visual task at post-viewing in the 3D condition were significant, with significant repeated measures correlations among them. Meanwhile, in the auditory task, the changes in cognitive performance and brain activity during the Go/NoGo blocks were not significant in the 3D condition. These results suggest that the failure or delay in the transmission of visual information to the primary somatosensory cortex due to visual fatigue induced by watching a 3D movie reduced the brain activity around the primary somatosensory cortex, resulting in poor cognitive performance for the visual task. This suggests that performing tasks that require visual information, such as running in the dark or driving a car, immediately after using a 3D application, may create unexpected risks in our lives. Thus, the findings of this study will help outlining precautions for the use of 3D applications.

The associations between suicide-related behaviors, prefrontal dysfunction in emotional cognition, and personality traits in mood disorders

Suicide is a serious public health problem, and it is urgent to identify biomarkers associated with suicide to prevent it. We aimed to clarify the association across suicidal behavior, personality traits, and brain activation by emotional stimulation tasks using near-infrared spectroscopy (NIRS) in patients with mood disorders. 11 mood disorder patients with a history of suicide attempt (MDSA), 18 mood disorder patients with no history of suicide attempt (MDNSA), and 17 healthy individuals were studied. The MDSA patients showed significantly high impulsivity and hopeless compared to healthy subjects, great response to the thread word task in the orbitofrontal cortex (OFC) and dorsolateral prefrontal cortex (DLPFC) compared to MDNSA patients, and the significant correlation between the personality traits and brain activation. The MDNSA did not show the trend. The results suggest that the personality traits and the activation of OFC and DLPFC during the negative emotional cognitive stimuli is associated with suicidal behavior, indicating the findings are involved in the pathophysiology of suicidality in mood disorders.

Deep neural network to differentiate brain activity between patients with euthymic bipolar disorders and healthy controls during verbal fluency performance: A multichannel near-infrared spectroscopy study

In this study, we aimed to differentiate between euthymic bipolar disorder (BD) patients and healthy controls (HC) based on frontal activity measured by fNIRS that were converted to spectrograms with Convolutional Neural Networks (CNN). And also, we investigated brain regions that cause this distinction. In total, 29 BD patients and 28 HCs were recruited. Their brain cortical activities were measured using fNIRS while performing letter versions of VFT. Each one of the 24 fNIRS channels was converted to a 2D spectrogram on which a CNN architecture was designed and utilized for classification. We found that our CNN algorithm using fNIRS activity during a VFT is able to differentiate subjects with BD from healthy controls with 90% accuracy, 80% sensitivity, and 100% specificity. Moreover, validation performance reached an AUC of 94%. From our individual channel analyses, we observed channels corresponding to the left inferior frontal gyrus (left-IFC), medial frontal cortex (MFC), right dorsolateral prefrontal cortex (DLPFC), Broca area, and right premotor have considerable activity variation to distinguish patients from HC. fNIRS activity during VFT can be used as a potential marker to classify euthymic BD patients from HCs. Activity particularly in the MFC, left-IFC, Broca's area, and DLPFC have a considerable variation to distinguish patients from healthy controls.

Multimodal resting-state connectivity predicts affective neurofeedback performance

Neurofeedback has been suggested as a potential complementary therapy to different psychiatric disorders. Of interest for this approach is the prediction of individual performance and outcomes. In this study, we applied functional connectivity-based modeling using electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) modalities to (i) investigate whether resting-state connectivity predicts performance during an affective neurofeedback task and (ii) evaluate the extent to which predictive connectivity profiles are correlated across EEG and fNIRS techniques. The fNIRS oxyhemoglobin and deoxyhemoglobin concentrations and the EEG beta and gamma bands modulated by the alpha frequency band (beta-m-alpha and gamma-m-alpha, respectively) recorded over the frontal cortex of healthy subjects were used to estimate functional connectivity from each neuroimaging modality. For each connectivity matrix, relevant edges were selected in a leave-one-subject-out procedure, summed into "connectivity summary scores" (CSS), and submitted as inputs to a support vector regressor (SVR). Then, the performance of the left-out-subject was predicted using the trained SVR model. Linear relationships between the CSS across both modalities were evaluated using Pearson's correlation. The predictive model showed a mean absolute error smaller than 20%, and the fNIRS oxyhemoglobin CSS was significantly correlated with the EEG gamma-m-alpha CSS (r = -0.456, p = 0.030). These results support that pre-task electrophysiological and hemodynamic resting-state connectivity are potential predictors of neurofeedback performance and are meaningfully coupled. This investigation motivates the use of joint EEG-fNIRS connectivity as outcome predictors, as well as a tool for functional connectivity coupling investigation.

A study of dynamic hand orthosis combined with unilateral task-oriented training in subacute stroke: A functional near-infrared spectroscopy case series

Background

Motor dysfunction in the upper extremities after stroke prohibits people with stroke from being independent in daily living. The application of fNIRS to explore brain activity under rehabilitation intervention is a research focus on neurorehabilitation.

Objective

The purpose of this study was to explore, using a grip-release ring motor task, the activated changes of regions of interest and changes in motor function utilizing fNIRS technology and test scales on persons with stroke who received unilateral task-oriented therapy with a hand orthosis in the early subacute stroke period before and after intervention. The study aimed to find a sensitive motor task and region of interest first, then to evaluate the feasibility and mechanism of this rehabilitation method by utilizing fNIRS technology in the next randomized controlled trial.

Methods

In this case series, eight right-handed, right hemiplegia subacute stroke persons (6 males,2 females from age 47 to 72) were enrolled. They received 30 min of unilateral task-oriented therapy without orthosis and 30 min of unilateral task-oriented therapy with orthosis (5 days/week) for 4 weeks. Activated channel numbers and beta values based on oxygenated hemoglobin concentration change using a grip-release ring motor task were estimated with fNIRS. Clinical outcome measures, including grip strength evaluation, action research arm test, and Fugl-Meyer assessment of the arm, were evaluated at the same time.

Results

Individual activation analysis showed that, after intervention, Subjects 1, 2, 6, 7, and 8 had the maximum mean beta value located in the left premotor cortex, while Subjects 4 and 5 had the maximum mean beta value located in the left sensorimotor cortex. The activation analysis of Subject 3 showed the maximum mean beta value located in the right premotor cortex. Deactivations of left sensorimotor cortex, left premotor cortex, and bilateral prefrontal cortex were observed after intervention which were different from other cases. Group activation analysis showed that bilateral cerebral hemispheres were activated in all eight participants, with right hemisphere and right supplementary motor cortex activated dominantly. After the intervention, the activation of bilateral hemispheres decreased but in different brain regions; there was a trend that the activation intensity of left sensorimotor cortex, right premotor cortex, and right prefrontal cortex decreased while activation intensity of left premotor cortex and left prefrontal cortex increased. Each participant demonstrated improvements in all the clinical test scales after intervention.

Conclusions

Left premotor cortex, left sensorimotor cortex, and right supplementary motor cortex may be the primary regions of interest. Grasp-release ring task was not appropriate to achieve our fNIRS research objective and a more sensitive motor task or more sensitive evaluating indicator should be used in further studies.

Interpersonal neural synchrony when predicting others' actions during a game of rock-paper-scissors

As members of a social species, we spend most of our time interacting with others. In interactions, we tend to mutually align our behavior and brain responses to communicate more effectively. In a semi-computerized version of the Rock-Paper-Scissors game, we investigated whether people show enhanced interpersonal neural synchronization when making explicit predictions about others' actions. Across four experimental conditions, we measured the dynamic brain activity using the functional near-infrared spectroscopy (fNIRS) hyperscanning method. Results showed that interpersonal neural synchrony was enhanced when participants played the game together as they would do in real life in comparison to when they played the game on their own. We found no evidence of increased neural synchrony when participants made explicit predictions about others' actions. Hence, neural synchrony may depend on mutual natural interaction rather than an explicit prediction strategy. This study is important, as it examines one of the presumed functions of neural synchronization namely facilitating predictions.

Influence of the Somatic Rubber Hand Illusion on Maximum Grip Aperture

The classic rubber hand illusion (RHI), based on visual, proprioceptive, and tactile feedback, can affect actions. However, it is not known whether these effects still occur if the paradigm is administered without visual feedback. In this study, we used the somatic RHI to test in thirty-two healthy individuals whether the incorporation of the rubber hand based on proprioceptive and tactile information only is sufficient to generate changes in actions. We measured maximum grip aperture (GA) changes towards a target and associated brain activations within the dorsal stream before and after the somatic RHI. Behavioural and neuroimaging data do not support an effect on maximum GA when the RHI is based on proprioceptive and tactile information only.

Neuroergonomic assessment of developmental coordination disorder

Until recently, neural assessments of gross motor coordination could not reliably handle active tasks, particularly in realistic environments, and offered a narrow understanding of motor-cognition. By applying a comprehensive neuroergonomic approach using optical mobile neuroimaging, we probed the neural correlates of motor functioning in young people with Developmental Coordination Disorder (DCD), a motor-learning deficit affecting 5-6% of children with lifelong complications. Neural recordings using fNIRS were collected during active ambulatory behavioral task execution from 37 Typically Developed and 48 DCD Children who performed cognitive and physical tasks in both single and dual conditions. This is the first of its kind study targeting regions of prefrontal cortical dysfunction for identification of neuropathophysiology for DCD during realistic motor tasks and is one of the largest neuroimaging study (across all modalities) involving DCD. We demonstrated that DCD is a motor-cognitive disability, as gross motor /complex tasks revealed neuro-hemodynamic deficits and dysfunction within the right middle and superior frontal gyri of the prefrontal cortex through functional near infrared spectroscopy. Furthermore, by incorporating behavioral performance, decreased neural efficiency in these regions were revealed in children with DCD, specifically during motor tasks. Lastly, we provide a framework, evaluating disorder impact in ecologically valid contexts to identify when and for whom interventional approaches are most needed and open the door for precision therapies.

Reduced temporal activation during a verbal fluency test in clinical high risk of psychosis: a functional near-infrared spectroscopy-based study

Background

Clinical high risk (CHR) of psychosis is a state in which positive symptoms cause the subjects distress but do not approach a severity level that fulfils the criteria for a psychotic episode. CHR exhibits cognitive deficits; however, the underlying neurobiological mechanisms remain unclear. This study aimed to investigate whether brain activation measured by the levels of oxygenated hemoglobin (oxy-Hb) in CHR subjects could be correlated with cognitive deficits.

Methods

Fifty-eight CHR individuals who fulfilled the criteria for attenuated positive syndrome as specified in the Structured Interview for Prodromal Syndrome (SIPS) and the Scale of Prodromal Syndrome (SOPS) and 58 age- and sex-matched healthy participants were included in the study. All subjects completed the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) that includes tests measuring attention, verbal memory, verbal fluency, executive function, and general intelligence. Functional near-infrared spectroscopy (fNIRS) was used to measure the level of oxy-Hb in the dorsolateral prefrontal and frontotemporal cortices.

Results

We observed significantly decreased oxy-Hb levels in channel 32 (located in the right superior temporal gyrus, rSTG)) within the CHR individuals compared with that in the healthy controls (HCs) (t=−3.44, Bonferroni-corrected p=0.002), indicating lower brain activity. A significant positive correlation was observed between task-related β values and working memory in the CHR group (r=0.35, p=0.008).

Conclusions

The brain activation of rSTG is abnormal among subjects at clinicial high risk for psychosis. This abnormality is probably associated with the neural mechanisms of deficits in the working memory during the early stage of psychosis.

Frequency-domain analysis of fNIRS fluctuations induced by rhythmic mental arithmetic

Functional near‐infrared spectroscopy (fNIRS) is an increasingly used technology for imaging neural correlates of cognitive processes. However, fNIRS signals are commonly impaired by task‐evoked and spontaneous hemodynamic oscillations of non‐cerebral origin, a major challenge in fNIRS research. In an attempt to isolate the task‐evoked cortical response, we investigated the coupling between hemodynamic changes arising from superficial and deep layers during mental effort. For this aim, we applied a rhythmic mental arithmetic task to induce cyclic hemodynamic fluctuations suitable for effective frequency‐resolved measurements. Twenty university students aged 18–25 years (eight males) underwent the task while hemodynamic changes were monitored in the forehead using a newly developed NIRS device, capable of multi‐channel and multi‐distance recordings. We found significant task‐related fluctuations for oxy‐ and deoxy‐hemoglobin, highly coherent across shallow and deep tissue layers, corroborating the strong influence of surface hemodynamics on deep fNIRS signals. Importantly, after removing such surface contamination by linear regression, we show that the frontopolar cortex response to a mental math task follows an unusual inverse oxygenation pattern. We confirm this finding by applying for the first time an alternative method to estimate the neural signal, based on transfer function analysis and phasor algebra. Altogether, our results demonstrate the feasibility of using a rhythmic mental task to impose an oscillatory state useful to separate true brain functional responses from those of non‐cerebral origin. This separation appears to be essential for a better understanding of fNIRS data and to assess more precisely the dynamics of the neuro‐visceral link.

We proposed the use of rhythmic mental arithmetic tasks to induce cyclic oscillations in multi‐distance fNIRS signals measured on the forehead, suitable for effective frequency‐domain analysis to better identify the actual neural functional response. We confirm the impairment of deep signals by task‐evoked non‐cerebral confounds, while providing evidence for an inverse oxygenation response in the frontopolar cortex.