Demographic reporting and phenotypic exclusion in fNIRS

Conceptualizing an antiracist framework for neuroscience research in art therapy: a qualitative pilot study

Introduction

Advances in social cognitive neuroscience research have contributed deeper understanding of neural processes relevant to art therapy, and of social, interrelational phenomena including racism and implicit bias. Confoundingly, emerging critical discourse about neuroscience research design highlighted systemic racism, implicit bias, and inequality perpetuated by imaging technologies, lack of diversity, and funding disparities. Emphasis toward antiracist practices within cognitive neuroscience research and various other fields has grown; however, literature on antiracist research practices within art therapy research is scant.

Methods

The purpose of this qualitative pilot research study was to elicit conceptualizations about antiracist research practices from art therapy researchers in response to relevant literature. Purposive sampling was used to recruit four female art therapy researchers from the United States (U.S.) and Europe. Semi-structured interviews were analyzed using grounded theory coding resulting in three main categories, seven themes, and subthemes. Member-checking and reflexive journaling were employed to enhance credibility.

Results

Core categories revealed points of convergence across participants, areas of concern, and requirements outlining antiracist research practices in art therapy. The first core category, shared beliefs and values, had three themes: neuroscience-informed perspective of art therapy; neuroscience research can strengthen art therapy theories; and infusion of antiracism and neuroscience into art therapy begins with education. The second core category, barriers and challenges, had two themes: potential credibility and legitimacy concerns for art therapy; and difficult conversations about disparities in awareness, diversity, and resources. The third core category, requirements and responsibilities for antiracist research, had two themes: due diligence to build accountability and legitimacy; and inclusion of diversity in art therapy research, and subthemes.

Discussion

Preliminary outcomes revealed ideas aligning current antiracist neuroscience research discourse with art therapy experimental research practices. The small group of neuroscience-focused art therapist researchers provided realistic considerations about amplifying discourse within the art therapy profession and infusing antiracist research into neuro-informed art therapy curriculum, and prioritizing diversity throughout experimental research design. An antiracist art therapy research framework with principles including education, intentionality, and diversity was proposed, along with recommendations for further research using the framework and to implement the framework into graduate art therapy education.

Simultaneous EEG and fNIRS recordings for semantic decoding of imagined animals and tools

Semantic neural decoding aims to identify which semantic concepts an individual focuses on at a given moment based on recordings of their brain activity. We investigated the feasibility of semantic neural decoding to develop a new type of brain-computer interface (BCI) that allows direct communication of semantic concepts, bypassing the character-by-character spelling used in current BCI systems. We provide data from our study to differentiate between two semantic categories of animals and tools during a silent naming task and three intuitive sensory-based imagery tasks using visual, auditory, and tactile perception. Participants were instructed to visualize an object (animal or tool) in their minds, imagine the sounds produced by the object, and imagine the feeling of touching the object. Simultaneous electroencephalography (EEG) and near-infrared spectroscopy (fNIRS) signals were recorded from 12 participants. Additionally, EEG signals were recorded from 7 other participants in a follow-up experiment focusing solely on the auditory imagery task. These datasets can serve as a valuable resource for researchers investigating semantic neural decoding, brain-computer interfaces, and mental imagery.

Modality-level obstacles and initiatives to improve representation in fetal, infant, and toddler neuroimaging research samples

Fetal, infant, and toddler (FIT) neuroimaging researchers study early brain development to gain insights into neurodevelopmental processes and identify early markers of neurobiological vulnerabilities to target for intervention. However, the field has historically excluded people from global majority countries and from marginalized communities in FIT neuroimaging research. Inclusive and representative samples are essential for generalizing findings across neuroimaging modalities, such as magnetic resonance imaging, magnetoencephalography, electroencephalography, functional near-infrared spectroscopy, and cranial ultrasonography. These FIT neuroimaging techniques pose unique and overlapping challenges to equitable representation in research through sampling bias, technical constraints, limited accessibility, and insufficient resources. The present article adds to the conversation around the need to improve inclusivity by highlighting modality-specific historical and current obstacles and ongoing initiatives. We conclude by discussing tangible solutions that transcend individual modalities, ultimately providing recommendations to promote equitable FIT neuroscience.

Do Children's Brains Function Differently During Book Reading and Screen Time? A fNIRS Study

Previous research suggests that book reading and screen time have contrasting effects on language and brain development. However, few studies have explicitly investigated whether children's brains function differently during these two activities. The present study used functional near-infrared spectroscopy (fNIRS) to measure brain response in 28 typically developing preschool-aged children (36-72 months old) during two conditions-a book reading condition, in which children listened to a story read by a live experimenter while viewing words and pictures in a book, and a screen time condition, in which children listened to a story that was played via an audio recording while viewing words and pictures on a screen. Analyses revealed significant activation in the right temporal parietal junction (TPJ) during the book reading condition only. Across regions of interest (ROIs), including the inferior and middle frontal gyrus (IMFG), the superior and middle temporal gyrus (SMTG), and the TPJ, brain response during the book reading condition was greater in right-lateralized ROIs than left-lateralized ROIs, while brain response during the screen time condition was similar across left and right ROIs. Findings suggest that the lateralization of preschool-aged children's brain function within these ROIs differs during book reading and screen time, which provides a possible neurobiological explanation for why book reading and screen time impact language development in such different ways. Findings provide important insights into how children's brains function during different types of activities (dyadic vs. solitary) and when using different types of media (print vs. digital).

Exploring Graph Theory Mechanisms of Fluid Intelligence in the DLPFC: Insights From Resting-State fNIRS Across Various Time Windows

BACKGROUND

Brain imaging technologies can measure fluid intelligence (gF) levels more directly, objectively, and dynamically, compared to traditional questionnaire scales. To clarify the temporal mechanisms of graph theory in measuring gF, this study investigated the relationship between graph theoretical indicators in the dorsolateral prefrontal cortex (DLPFC) and gF levels under various time windows.

METHODS

Using 30-min resting-state fNIRS (rs-fNIRS) data and Raven's Advanced Progressive Matrices from 116 healthy participants, the relationship between individual gF levels and DLPFC brain signals was analyzed using average degree (AD) and global efficiency (Eglob).

RESULTS

AD and Eglob in the resting-state DLPFC were significantly negatively correlated with the RAPM score. Considering the effectiveness and efficiency of gF measurement, a 2-min data collection might suffice, while for Eglob, more than 15-min collection was more effective.

CONCLUSION

These findings help clarify brain indicators and demonstrate the effectiveness of rs-fNIRS in intelligence measurement, providing a theoretical and practical basis for portable and objective gF assessment .

Wearable Wireless Functional Near-Infrared Spectroscopy System for Cognitive Activity Monitoring

From learning environments to battlefields to marketing teams, the desire to measure cognition and cognitive fatigue in real time has been a grand challenge in optimizing human performance. Near-infrared spectroscopy (NIRS) is an effective optical technique for measuring changes in subdermal hemodynamics, and it has been championed as a more practical method for monitoring brain function compared to MRI. This study reports on an innovative functional NIRS (fNIRS) sensor that integrates the entire system into a compact and wearable device, enabling long-term monitoring of patients. The device provides unrestricted mobility to the user with a Bluetooth connection for settings configuration and data transmission. A connected device, such as a smartphone or laptop equipped with the appropriate interface software, collects raw data, then stores and generates real-time analyses. Tests confirm the sensor is sensitive to oxy- and deoxy-hemoglobin changes on the forehead region, which indicate neuronal activity and provide information for brain activity monitoring studies.

Empathy and helping: the role of affect in response to others' suffering

Decades of research hold that empathy is a multifaceted construct. A related challenge in empathy research is to describe how each subcomponent of empathy uniquely contributes to social outcomes. Here, we examined distinct mechanisms through which different components of empathy-Empathic Concern, Perspective Taking, and Personal Distress-may relate to prosociality. Participants (N = 77) watched a prerecorded video of a person sharing an emotional real-life story and provided verbal support in response. The listeners then reported how positive and negative they felt while listening to the story. We found that individuals with greater tendencies to experience Empathic Concern and Perspective Taking felt more positive (e.g., connected, compassionate), whereas those with higher Personal Distress felt more negative (e.g., nervous, anxious) in response to another's suffering. We also observed indirect relationships between Empathic Concern / Perspective Taking and the tendency to help others through positive affective responses to the other's suffering. These findings build upon the growing literature that distinguishes different components of empathy and their mechanisms that relate to divergent behavioral consequences. Results also highlight the role of positive affect that may motivate prosociality in the face of others' suffering.

Physiological influences on neurovascular coupling: A systematic review of multimodal imaging approaches and recommendations for future study designs

In this review, we have amalgamated the literature, taking a multimodal neuroimaging approach to quantify the relationship between neuronal firing and haemodynamics during a task paradigm (i.e., neurovascular coupling response), while considering confounding physiological influences. Original research articles that used concurrent neuronal and haemodynamic quantification in humans (n ≥ 10) during a task paradigm were included from PubMed, Scopus, Web of Science, EMBASE and PsychINFO. Articles published before 31 July 2023 were considered for eligibility. Rapid screening was completed by the first author. Two authors completed the title/abstract and full-text screening. Article quality was assessed using a modified version of the National Institutes of Health Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. A total of 364 articles were included following title/abstract and full-text screening. The most common combination was EEG/functional MRI (68.7%), with cognitive (48.1%) and visual (27.5%) tasks being the most common. The majority of studies displayed an absence/minimal control of blood pressure, arterial gas concentrations and/or heart rate (92.9%), and only 1.3% monitored these factors. A minority of studies restricted or collected data pertaining to caffeine (7.4%), exercise (0.8%), food (0.5%), nicotine (2.7%), the menstrual cycle (0.3%) or cardiorespiratory fitness levels (0.5%). The cerebrovasculature is sensitive to numerous factors; thus, to understand the neurovascular coupling response fully, better control for confounding physiological influences of blood pressure and respiratory metrics is imperative during study-design formulation. Moreover, further work should continue to examine sex-based differences, the influence of sex steroid hormone concentrations and cardiorespiratory fitness.

Comparative Neuroexcitation Patterns Using fNIRS in Women With Overactive Bladder

IMPORTANCE

Functional near-infrared spectroscopy (fNIRS) is a noninvasive technique used to quantify prefrontal cortex (PFC) neuroexcitation. The PFC is involved in the decision to void, and dysfunction in the region has been associated with overactive bladder (OAB). This study demonstrates neuroexcitation differences in the brain region associated with the decision to void (prefrontal cortex) using noninvasive fNIRS.

OBJECTIVE

The objective of this study was to compare PFC neuroexcitation during natural filling in female participants with and without OAB.

STUDY DESIGN

Female participants with OAB were cross-sectionally compared with controls without urinary urgency. The fNIRS signals were continuously recorded during an oral hydration protocol. Simultaneously, recordings of real-time bladder sensation of fullness were completed. A period of "high sensation" was defined as the time from first desire to 100% sensation. Signal analysis included removal of motion artifact, low pass filtering, and interpolated to standardize reporting bladder filling time.

RESULTS

A total of 25 female participants were enrolled and had complete analyzable data, including 14 with OAB and 11 controls without OAB. Change in O2Hb during the high sensation period was significantly lower in all PFC regions in the OAB group compared with controls (P < 0.001). The majority of OAB participants had a constant or decreasing neuroexcitation pattern, which differenced in comparison to normal controls who displayed an increasing pattern.

CONCLUSIONS

This study demonstrates that fNIRS PFC excitation during a period of high sensation is consistently lower in women with OAB as compared with controls. These data support the hypothesis that the PFC plays an inhibitory role in voiding function and that there may be a lack of inhibitory control in women with OAB.

Dynamic Field Theory of Executive Function: Identifying Early Neurocognitive Markers

In this Monograph, we explored neurocognitive predictors of executive function (EF) development in a cohort of children followed longitudinally from 30 to 54 months of age. We tested predictions of a dynamic field model that explains development in a benchmark measure of EF development, the dimensional change card sort (DCCS) task. This is a rule-use task that measures children's ability to switch between sorting cards by shape or color rules. A key developmental mechanism in the model is that dimensional label learning drives EF development. Data collection began in February 2019 and was completed in April 2022 on the Knoxville campus of the University of Tennessee. Our cohort included 20 children (13 female) all of whom were White (not Hispanic/Latinx) from an urban area in southern United States, and the sample annual family income distribution ranged from low to high (most families falling between $40,000 and 59,000 per year (note that we address issues of generalizability and the small sample size throughout the monograph)). We tested the influence of dimensional label learning on DCCS performance by longitudinally assessing neurocognitive function across multiple domains at 30 and 54 months of age. We measured dimensional label learning with comprehension and production tasks for shape and color labels. Simple EF was measured with the Simon task which required children to respond to images of a cat or dog with a lateralized (left/right) button press. Response conflict was manipulated in this task based on the spatial location of the stimulus which could be neutral (central), congruent, or incongruent with the spatial lateralization of the response. Dimensional understanding was measured with an object matching task requiring children to generalize similarity between objects that matched within the dimensions of color or shape. We first identified neural measures associated with performance and development on each of these tasks. We then examined which of these measures predicted performance on the DCCS task at 54 months. We measured neural activity with functional near-infrared spectroscopy across bilateral frontal, temporal, and parietal cortices. Our results identified an array of neurocognitive mechanisms associated with development within each domain we assessed. Importantly, our results suggest that dimensional label learning impacts the development of EF. Neural activation in left frontal cortex during dimensional label production at 30 months of age predicted EF performance at 54 months of age. We discussed these results in the context of efforts to train EF with broad transfer. We also discussed a new autonomy-centered EF framework. The dynamic field model on which we have motivated the current research makes decisions autonomously and various factors can influence the types of decisions that the model makes. In this way, EF is a property of neurocognitive dynamics, which can be influenced by individual factors and contextual effects. We also discuss how this conceptual framework can generalize beyond the specific example of dimensional label learning and DCCS performance to other aspects of EF and how this framework can help to understand how EF unfolds in unique individual, cultural, and contextual factors. Measures of EF during early childhood are associated with a wide range of development outcomes, including academic skills and quality of life. The hope is that broad aspects of development can be improved by implementing interventions aimed at facilitating EF development. However, this promise has been largely unrealized. Previous work on EF development has been limited by a focus on EF components, such as inhibition, working memory, and switching. Similarly, intervention research has focused on practicing EF tasks that target these specific components of EF. While performance typically improves on the practiced task, improvement rarely generalizes to other EF tasks or other developmental outcomes. The current work is unique because we looked beyond EF itself to identify the lower-level learning processes that predict EF development. Indeed, the results of this study identify the first learning mechanism involved in the development of EF. Although the work here provides new targets for interventions in future work, there are also important limitations. First, our sample is not representative of the underlying population of children in the United States under the age of 5. This is a problem in much of the existing developmental cognitive neuroscience research. We discussed challenges to the generalizability of our findings to the population at large. This is particularly important given that our theory is largely contextual, suggesting that children's unique experiences with learning labels for visual dimensions will impact EF development. Second, we identified a learning mechanism to target in future intervention research; however, it is not clear whether such interventions would benefit all children or how to identify children who would benefit most from such interventions. We also discuss prospective lines of research that can address these limitations, such as targeting families that are typically underrepresented in research, expanding longitudinal studies to examine longer term outcomes such as school-readiness and academic skills, and using the dynamic field (DF) model to systematically explore how exposure to objects and labels can optimize the neural representations underlying dimensional label learning. Future work remains to understand how such learning processes come to define the contextually and culturally specific skills that emerge over development and how these skills lay the foundation for broad developmental trajectories.

Untangling bias: Racial and phenotypic bias in neuroimaging methods must be addressed

Racial and phenotypic bias in neuroimaging methods must be addressed.

Aesthetic evaluation of body movements shaped by embodied and arts experience: Insights from behaviour and fNIRS

Aesthetic appreciation of full-body movements is likely shaped by our cumulative bodily experiences, yet most of the extant literature in this domain has focused on expertise and familiarity. We ran two experiments exploring individual differences in embodied experience and experience with the arts: In Study 1, we explored how participants' (n = 41) abilities to learn a choreography shaped their aesthetic perceptions while viewing learned vs. unknown movements, using functional near-infrared spectroscopy (fNIRS) to measure cortical activation over the Action Observation Network (i.e., inferior frontal gyrus [IFG], inferior parietal lobule, middle temporal gyrus [MTG]). Study 1 demonstrated that embodied experience enhanced ratings of enjoyment, familiarity, and reproducibility of movements, and that individual differences in participants' performance of the learned choreography were not associated with aesthetic ratings, but rather cortical activation in IFG and right MTG while viewing learned choreography. In Study 2, we combined the behavioural data from Study 1 with data from additional participants (total n = 141) to examine the relationship between arts experience and aesthetic perceptions of movements robustly. Study 2 revealed that previous arts and sports experience correlated with aesthetic judgements of familiarity and reproducibility of movements. Our findings highlight the relevance of examining individual experiences to fill theoretical gaps in our understanding of action aesthetics.

Quantifying the Impact of Hair and Skin Characteristics on Signal Quality with Practical Recommendations for Improvement

Functional Near-Infrared Spectroscopy (fNIRS) holds transformative potential for research and clinical applications in neuroscience due to its non-invasive nature and adaptability to real-world settings. However, despite its promise, fNIRS signal quality is sensitive to individual differences in biophysical factors such as hair and skin characteristics, which can significantly impact the absorption and scattering of near-infrared light. If not properly addressed, these factors risk biasing fNIRS research by disproportionately affecting signal quality across diverse populations. Our results quantify the impact of various hair properties, skin pigmentation as well as head size, sex and age on signal quality, providing quantitative guidance for future hardware advances and methodological standards to help overcome these critical barriers to inclusivity in fNIRS studies. We provide actionable guidelines for fNIRS researchers, including a suggested metadata table and recommendations for cap and optode configurations, hair management techniques, and strategies to optimize data collection across varied participants. This research paves the way for the development of more inclusive fNIRS technologies, fostering broader applicability and improved interpretability of neuroimaging data in diverse populations.

Particles and Prejudice: Nanomedicine Approaches to Reducing Health Disparities in Endometrial Cancer

Endometrial cancer is the most common gynecological malignancy worldwide and unfortunately has a much higher mortality rate in Black women compared with White women. Many potential factors contribute to these mortality rates, including the underlying effects of systemic and interpersonal racism. Furthermore, other trends in medicine have potential links to these rates including participation in clinical trials, hormone therapy, and pre-existing health conditions. Addressing the high incidence and disparate mortality rates in endometrial cancer requires novel methods, such as nanoparticle-based therapeutics. These therapeutics have been growing in increasing prevalence in pre-clinical development and have far-reaching implications in cancer therapy. The rigor of pre-clinical studies is enhanced by the likeness of the model to the human body. In systems for 3D cell culture, for example, the extracellular matrix mimics the tumor more closely. The increasing emphasis on precision medicine can be applied to cancer using nanoparticle-based methods and applied to pre-clinical models by using patient-derived model data. This review highlights the intersections of nanomedicine, precision medicine, and racial disparities within endometrial cancer and provides insights into reducing health disparities using recent scientific advances on the nanoscale.

Customizable optode attachments to improve hair clearance timing and inclusiveness in functional near-infrared spectroscopy research

Significance

Functional near-infrared spectroscopy (fNIRS) is a promising alternative to functional magnetic resonance imaging for measuring brain activity, but the presence of hair reduces data quality.

Aim

To improve research efficiency and promote wider subject inclusivity, we developed the "Mini Comb"-an attachment for commercial fNIRS head caps that can rapidly clear hair with a simple twisting motion.

Approach

To test the utility of the Mini Comb on different hair types, we measured the clearance achieved with eight unique sliding leg extrusions on 10 wigged mannequins of various hair characteristics. Following mannequin testing, we recruited a total of 15 participants to evaluate the performance of the Mini Comb as pertains to the time needed to create clearance and the signal quality captured.

Results

The Mini Comb achieves comparable signal-to-noise ratios (SNRs) as standard hair clearance procedures while reducing hair clearance time by nearly 50%. Importantly, group analysis revealed better SNR results when the Mini Comb sliding leg design is matched to hair type, suggesting that consideration of hair type is important when conducting fNIRS studies.

Conclusions

The Mini Comb thus opens the door for the deployment of fNIRS for more widespread, inclusive, and comprehensive neuroimaging studies.

Pilot Evaluation of Sevo Systems for Epilepsy: Equitable EEG for Coarse, Dense, and Curly Hair

Collecting electroencephalography (EEG) data from individuals with coarse, curly, or afro-textured hair can be challenging, leading to noisier data, negative clinical outcomes (e.g., risk of misdiagnosis, discomfort, longer setup times, unsavory treatment, hair shaving, and microaggressions), and unreliable basic science conclusions due to the disproportionate exclusion of people with this physical feature worldwide. Our prior work demonstrated that strategically braiding hair to expose the scalp at standard locations improves impedance and that novel electrode adapters that we developed called "Sevo" can further lower impedance by more than 15x. In this article, we further quantify the signal quality of Sevo EEG compared to traditional EEG on a cohort of pediatric epileptic patients and health adult volunteers. We assessed the influence of braiding and the use of Sevo adapters on signal quality and found that Sevo reduces noise in two key metrics of the power spectra, especially for the pediatric epilepsy group. We conclude by outlining best practices for preparing coarse, curly hair for use by EEG technicians, researchers, and patients.

Optimizing spatial specificity and signal quality in fNIRS: an overview of potential challenges and possible options for improving the reliability of real-time applications

The optical brain imaging method functional near-infrared spectroscopy (fNIRS) is a promising tool for real-time applications such as neurofeedback and brain-computer interfaces. Its combination of spatial specificity and mobility makes it particularly attractive for clinical use, both at the bedside and in patients' homes. Despite these advantages, optimizing fNIRS for real-time use requires careful attention to two key aspects: ensuring good spatial specificity and maintaining high signal quality. While fNIRS detects superficial cortical brain regions, consistently and reliably targeting specific regions of interest can be challenging, particularly in studies that require repeated measurements. Variations in cap placement coupled with limited anatomical information may further reduce this accuracy. Furthermore, it is important to maintain good signal quality in real-time contexts to ensure that they reflect the true underlying brain activity. However, fNIRS signals are susceptible to contamination by cerebral and extracerebral systemic noise as well as motion artifacts. Insufficient real-time preprocessing can therefore cause the system to run on noise instead of brain activity. The aim of this review article is to help advance the progress of fNIRS-based real-time applications. It highlights the potential challenges in improving spatial specificity and signal quality, discusses possible options to overcome these challenges, and addresses further considerations relevant to real-time applications. By addressing these topics, the article aims to help improve the planning and execution of future real-time studies, thereby increasing their reliability and repeatability.

Exploring the impact and influence of melanin on frequency-domain near-infrared spectroscopy measurements

Significance

Near-infrared spectroscopy (NIRS) is a non-invasive optical method that measures changes in hemoglobin concentration and oxygenation. The measured light intensity is susceptible to reduced signal quality due to the presence of melanin.

Aim

We quantify the influence of melanin concentration on NIRS measurements taken with a frequency-domain near-infrared spectroscopy system using 690 and 830 nm.

Approach

Using a forehead NIRS probe, we measured 35 healthy participants and investigated the correlation between melanin concentration indices, which were determined using a colorimeter, and several key metrics from the NIRS signal. These metrics include signal-to-noise ratio (SNR), two measurements of oxygen saturation (arterial oxygen saturation,SpO 2 , and tissue oxygen saturation,StO 2 ), and optical properties represented by the absorption coefficient (μ a ) and the reduced scattering coefficient (μ s ' ).

Results

We found a significant negative correlation between the melanin index and the SNR estimated in oxy-hemoglobin signals (r s = - 0.489 , p = 0.006 ) andSpO 2 levels (r s = - 0.413 , p = 0.023 ). However, no significant changes were observed in the optical properties andStO 2 (r s = - 0.146 , p = 0.44 ).

Conclusions

We found that estimated SNR andSpO 2 values show a significant decline and dependence on the melanin index, whereasStO 2 and optical properties do not show any correlation with the melanin index.

Opportunities and obstacles in non-invasive brain stimulation

Non-invasive brain stimulation (NIBS) is a complex and multifaceted approach to modulating brain activity and holds the potential for broad accessibility. This work discusses the mechanisms of the four distinct approaches to modulating brain activity non-invasively: electrical currents, magnetic fields, light, and ultrasound. We examine the dual stochastic and deterministic nature of brain activity and its implications for NIBS, highlighting the challenges posed by inter-individual variability, nebulous dose-response relationships, potential biases and neuroanatomical heterogeneity. Looking forward, we propose five areas of opportunity for future research: closed-loop stimulation, consistent stimulation of the intended target region, reducing bias, multimodal approaches, and strategies to address low sample sizes.

On decoding of rapid motor imagery in a diverse population using a high-density NIRS device

Introduction

Functional near-infrared spectroscopy (fNIRS) aims to infer cognitive states such as the type of movement imagined by a study participant in a given trial using an optical method that can differentiate between oxygenation states of blood in the brain and thereby indirectly between neuronal activity levels. We present findings from an fNIRS study that aimed to test the applicability of a high-density (>3000 channels) NIRS device for use in short-duration (2 s) left/right hand motor imagery decoding in a diverse, but not explicitly balanced, subject population. A side aim was to assess relationships between data quality, self-reported demographic characteristics, and brain-computer interface (BCI) performance, with no subjects rejected from recruitment or analysis.

Methods

BCI performance was quantified using several published methods, including subject-specific and subject-independent approaches, along with a high-density fNIRS decoder previously validated in a separate study.

Results

We found that decoding of motor imagery on this population proved extremely challenging across all tested methods. Overall accuracy of the best-performing method (the high-density decoder) was 59.1 +/- 6.7% after excluding subjects where almost no optode-scalp contact was made over motor cortex and 54.7 +/- 7.6% when all recorded sessions were included. Deeper investigation revealed that signal quality, hemodynamic responses, and BCI performance were all strongly impacted by the hair phenotypical and demographic factors under investigation, with over half of variance in signal quality explained by demographic factors alone.

Discussion

Our results contribute to the literature reporting on challenges in using current-generation NIRS devices on subjects with long, dense, dark, and less pliable hair types along with the resulting potential for bias. Our findings confirm the need for increased focus on these populations, accurate reporting of data rejection choices across subject intake, curation, and final analysis in general, and signal a need for NIRS optode designs better optimized for the general population to facilitate more robust and inclusive research outcomes.

How parent-child brain-to-brain synchrony can inform the study of child development

It is well established that parent-child dyadic synchrony (e.g., mutual emotions, behaviors) can support development across cognitive and socioemotional domains. The advent of simultaneous two-brain hyperscanning (i.e., neuroimaging techniques to measure the brain activity of two individuals at the same time) allows further insight into dyadic neural synchrony. In this article, we review 16 recent studies of naturalistic, parent-child brain-to-brain synchrony, finding relations with the nature of interactions (collaborative versus competitive, parent versus stranger), proximal social cues (gaze, affect, touch, reciprocity), child-level variables (irritability, self-regulation), and environmental factors (parental stress, family cohesion, adversity). We then discuss how neural synchrony may provide a biological mechanism for refining broader theories on developmental benefits of dyadic synchrony. We also highlight critical areas for future study, including examining synchrony trajectories longitudinally, including more diverse participants and interaction contexts, and studying caregivers beyond mothers (e.g., other family members, teachers). We conclude that neural synchrony is an exciting and important window into understanding how caregiver-child dyadic synchrony supports children's social and cognitive development.

Atypical brain lateralization for speech processing at the sublexical level in autistic children revealed by fNIRS

Autistic children often exhibit atypical brain lateralization of language processing, but it is unclear what aspects of language contribute to this phenomenon. This study employed functional near-infrared spectroscopy to measure hemispheric lateralization by estimating hemodynamic responses associated with processing linguistic and non-linguistic auditory stimuli. The study involved a group of autistic children (N = 20, mean age = 5.8 years) and a comparison group of nonautistic peers (N = 20, mean age = 6.5 years). The children were presented with stimuli with systematically decreasing linguistic relevance: naturalistic native speech, meaningless native speech with scrambled word order, nonnative speech, and music. The results revealed that both groups showed left lateralization in the temporal lobe when listening to naturalistic native speech. However, the distinction emerged between autism and nonautistic in terms of processing the linguistic hierarchy. Specifically, the nonautistic comparison group demonstrated a systematic reduction in left lateralization as linguistic relevance decreased. In contrast, the autism group displayed no such pattern and showed no lateralization when listening to scrambled native speech accompanied by enhanced response in the right hemisphere. These results provide evidence of atypical neural specialization for spoken language in preschool- and school-age autistic children and shed new light on the underlying linguistic correlates contributing to such atypicality at the sublexical level.

Mobile fNIRS for exploring inter-brain synchrony across generations and time

While still relatively rare, longitudinal hyperscanning studies are exceptionally valuable for documenting changes in inter-brain synchrony, which may in turn underpin how behaviors develop and evolve in social settings. The generalizability and ecological validity of this experimental approach hinges on the selected imaging technique being mobile-a requirement met by functional near-infrared spectroscopy (fNIRS). fNIRS has most frequently been used to examine the development of inter-brain synchrony and behavior in child-parent dyads. In this position paper, we contend that dedicating attention to longitudinal and intergenerational hyperscanning stands to benefit the fields of social and cognitive neuroscience more broadly. We argue that this approach is particularly relevant for understanding the neural mechanisms underpinning intergenerational social dynamics, and potentially for benchmarking progress in psychological and social interventions, many of which are situated in intergenerational contexts. In line with our position, we highlight areas of intergenerational research that stand to be enhanced by longitudinal hyperscanning with mobile devices, describe challenges that may arise from measuring across generations in the real world, and offer potential solutions.

The Role of the Dorsolateral Prefrontal Cortex in the Production and Comprehension of Phonologically and Semantically Related Words

Previous studies suggest that producing and comprehending semantically related words relies on inhibitory control over competitive lexical selection which results in the recruitment of the left inferior frontal gyrus (IFG). Few studies, however, have examined the involvement of other regions of the frontal cortex, such as the dorsolateral prefrontal cortex (DLPFC), despite its role in cognitive control related to lexical processing. The primary objective of this study was to elucidate the role of the DLPFC in the production and comprehension of semantically and phonologically related words in blocked cyclic naming and picture-word matching paradigms. Twenty-one adults participated in neuroimaging with functional near-infrared spectroscopy to measure changes in oxygenated and deoxygenated hemoglobin concentrations across the bilateral frontal cortex during blocked cyclic picture naming and blocked cyclic picture-word-matching tasks. After preprocessing, oxygenated and deoxygenated hemoglobin concentrations were obtained for each task (production, comprehension), condition (semantic, phonological) and region (DLPFC, IFG). The results of pairwise t-tests adjusted for multiple comparisons showed significant increases in oxygenated hemoglobin concentration over baseline in the bilateral DLPFC during picture naming for phonologically related words. For picture-word matching, we found significant increases in oxygenated hemoglobin concentration over baseline in the right DLPFC for semantically related words and in the right IFG for phonologically related words. We discuss the results in light of the inhibitory attentional control over competitive lexical access theory in contrast to alternative potential explanations for the findings.