Correlation between asymmetry of spontaneous oscillation of hemodynamic changes in the prefrontal cortex and anxiety levels: a near-infrared spectroscopy study

Capture of emotional responses under a simulated earthquake experience using near-infrared spectroscopy and virtual reality

AIM

In a previous study, we reported that watching two-dimensional videos of earthquakes significantly reduced sympathetic nerve activity in healthy young adults. In the present study, we aimed to investigate the emotional responses to earthquakes using immersive virtual reality (VR), which can provide a more realistic experience.

METHODS

In total, 24 healthy young adults (12 males, 21.4 ± 0.2 years old) participated. Participants were required to watch earthquake and neutral videos while wearing a head-mounted display and near-infrared spectroscopy (NIRS), during which physiological signals, including pulse rate and cerebral blood flow (CBF) in the dorsolateral prefrontal cortex, were measured. We also analyzed changes in sympathetic and parasympathetic indices and obtained seven emotion ratings: valence, arousal, dominance, fear, astonishment, anxiety, and panic.

RESULTS

The VR earthquake videos evoked negative subjective emotions, and the pulse rate significantly decreased. Sympathetic nerve activity tended to decrease, whereas CBF in the left prefrontal cortex showed a slight increase, although this was not significant.

CONCLUSIONS

This study showed that measurements combined with NIRS and immersive VR have the potential to capture emotional responses to different stimuli.

Exploring sexual dimorphism in basal forebrain volume changes during aging and neurodegenerative diseases

Patients with neurodegenerative diseases exhibit diminished basal forebrain (BF) volume compared to healthy individuals. However, it's uncertain whether this difference is consistent between sexes. It has been reported that BF volume moderately atrophies during aging, but the effect of sex on BF volume changes during the normal aging process remains unclear. In the cross-sectional study, we observed a significant reduction in BF volume in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) compared to Healthy Controls (HCs), especially in the Ch4 subregion. Notably, significant differences in BF volume between MCI and HCs were observed solely in the female group. Additionally, we identified asymmetrical atrophy in the left and right Ch4 subregions in female patients with AD. In the longitudinal analysis, we found that aging seemed to have a minimal impact on BF volume in males. Our study highlights the importance of considering sex as a research variable in brain science.

Bifidobacterium breve M-16V regulates the autonomic nervous system via the intestinal environment: A double-blind, placebo-controlled study

We conducted a randomized controlled trial to investigate the potential of Bifidobacterium breve M-16 V to improve mood in humans. In this evaluation, we incorporated the use of near-infrared spectroscopy (NIRS), which has been used to evaluate mood states in studies with small sample sizes. Participants were given B. breve M-16 V (20 billion cells/day) for 6 weeks, and their mood state was assessed before and after ingestion. NIRS data were collected at rest and during a mental arithmetic task (under stress). Intake of B. breve M-16 V decreased the heart rate under stress and increased levels of the GABA-like substance pipecolic acid in stool samples. In addition, B. breve M-16 V improved mood and sleep scores in participants with high anxiety levels. These results suggest that B. breve M-16 V affects the metabolites of the gut microbiota and has the potential to modulate the autonomic nervous system and to improve mood and sleep.

fNIRS a novel neuroimaging tool to investigate olfaction, olfactory imagery, and crossmodal interactions: a systematic review

Olfaction is understudied in neuroimaging research compared to other senses, but there is growing evidence of its therapeutic benefits on mood and well-being. Olfactory imagery can provide similar health benefits as olfactory interventions. Harnessing crossmodal visual-olfactory interactions can facilitate olfactory imagery. Understanding and employing these cross-modal interactions between visual and olfactory stimuli could aid in the research and applications of olfaction and olfactory imagery interventions for health and wellbeing. This review examines current knowledge, debates, and research on olfaction, olfactive imagery, and crossmodal visual-olfactory integration. A total of 56 papers, identified using the PRISMA method, were evaluated to identify key brain regions, research themes and methods used to determine the suitability of fNIRS as a tool for studying these topics. The review identified fNIRS-compatible protocols and brain regions within the fNIRS recording depth of approximately 1.5 cm associated with olfactory imagery and crossmodal visual-olfactory integration. Commonly cited regions include the orbitofrontal cortex, inferior frontal gyrus and dorsolateral prefrontal cortex. The findings of this review indicate that fNIRS would be a suitable tool for research into these processes. Additionally, fNIRS suitability for use in naturalistic settings may lead to the development of new research approaches with greater ecological validity compared to existing neuroimaging techniques.

Preventing prefrontal dysfunction by tDCS modulates stress-induced creativity impairment in women: an fNIRS study

Stress is a major external factor threatening creative activity. The study explored whether left-lateralized activation in the dorsolateral prefrontal cortex manipulated through transcranial direct current stimulation could alleviate stress-induced impairment in creativity. Functional near-infrared spectroscopy was used to explore the underlying neural mechanisms. Ninety female participants were randomly assigned to three groups that received stress induction with sham stimulation, stress induction with true stimulation (anode over the left and cathode over the right dorsolateral prefrontal cortex), and control manipulation with sham stimulation, respectively. Participants underwent the stress or control task after the transcranial direct current stimulation manipulation, and then completed the Alternative Uses Task to measure creativity. Behavioral results showed that transcranial direct current stimulation reduced stress responses in heart rate and anxiety. The functional near-infrared spectroscopy results revealed that transcranial direct current stimulation alleviated dysfunction of the prefrontal cortex under stress, as evidenced by higher activation of the dorsolateral prefrontal cortex and frontopolar cortex, as well as stronger inter-hemispheric and intra-hemispheric functional connectivity within the prefrontal cortex. Further analysis demonstrated that the cortical regulatory effect prevented creativity impairment induced by stress. The findings validated the hemispheric asymmetry hypothesis regarding stress and highlighted the potential for brain stimulation to alleviate stress-related mental disorders and enhance creativity.

Acute hypoxia elicits prefrontal oxygenation asymmetry in young adults

Significance

Cerebrovascular reactivity can be evaluated by prefrontal cortex (PFC) hemodynamic responses and oxygenation changes secondary to hypoxia using near-infrared spectroscopy (NIRS). However, whether there are hemispheric differences in these NIRS-determined PFC hemodynamic responses and oxygenation changes remains unknown.

Aim

This study was performed to determine whether there are differences in the PFC hemodynamic responses and oxygenation changes secondary to hypoxia between the left and right frontal poles (FPL and FPR, respectively).

Approach

Fifteen young men participated in the study. During conduction of an isocapnic hypoxia protocol with a 10-min hypoxic phase at partial pressure of end-tidal oxygen (PET O 2 ) of 45 Torr, hemodynamic and oxygenation indices comprising oxygenated hemoglobin (oxy-Hb), deoxygenated Hb (deoxy-Hb), total Hb (total-Hb), and tissue oxygen saturation (StO 2 ) over FPL and FPR were measured by NIRS. The heart rate (HR) was evaluated by electrocardiography.

Results

In response to hypoxia, the HR increased, oxy-Hb decreased, deoxy-Hb increased, total-Hb increased above baseline, and StO 2 decreased. There was no difference in the change in total-Hb between FPL and FPR. However, there were greater changes in oxy-Hb, deoxy-Hb, and StO 2 over FPL than over FPR, indicating that PFC oxygenation asymmetry occurs in response to hypoxia. Moreover, the change in total-Hb over FPL was associated with the increase in HR.

Conclusions

NIRS-determined hemodynamic responses and oxygenation changes secondary to hypoxia might not simply reflect the direct effect of hypoxia on cerebral vessels. Although there is no hemispheric difference in the PFC hemodynamic responses to hypoxia as in total-Hb, PFC oxygenation asymmetry occurs in young adults.

The relationship between the prefrontal cortex and limb motor function in stroke: A study based on resting-state functional near-infrared spectroscopy

BACKGROUND

With the ageing of the world population, the incidence of stroke has been increasing annually, becoming a public health problem affecting adult health. Limb motor dysfunction is one of the common complications of stroke and an important factor in disability. Therefore, restoring limb function is an important task in current rehabilitation. Accurate assessment of motor function in stroke patients is the basis for formulating effective rehabilitation strategies. With the development of neuroimaging technology, scholars have begun to study objective evaluation methods for limb motor dysfunction in stroke to determine reliable neural biomarkers to accurately identify brain functional activity and its relationship with limb motor function. The prefrontal cortex (PFC) plays an important role in motor control and in response to motor state changes. Our previous study found that the PFC network characteristics of stroke patients are related to their motor function status and the topological properties of the PFC network under resting state can predict the motor function of stroke patients to some extent. Therefore, this study used functional near-infrared spectroscopy (fNIRS) to evaluate prefrontal neuroplasticity markers and the relationships between such neural markers and limb motor function in stroke patients with limb motor dysfunction, which could be helpful to further clarify the relationship between brain neuroplasticity and cerebral haemodynamics. At the same time, through accurate and objective means of evaluation, it could be helpful for clinicians to formulate and optimize individualized rehabilitation treatment plans and accurately determine the rehabilitation efficacy and prognosis.

METHODS

This study recruited 17 S patients with limb motor dysfunction and 9 healthy subjects. fNIRS was used to collect 22 channels of cerebral blood oxygen signals in the PFC in the resting state. The differences in prefrontal oxygenated haemoglobin (HbO) and deoxygenated haemoglobin (HbR) concentrations were analysed between stroke patients and healthy subjects, and the lateralization index (LI) of HbO in stroke patients was also calculated. Pearson's correlation analysis was performed between the LI and the scores of the Fugl-Meyer Assessment Scale (FMA) of motor function in stroke patients.

RESULTS

The results found that the prefrontal HbO concentration was significantly decreased in stroke patients with limb motor dysfunction compared with healthy subjects, and there was a significant, positive correlation between the LI of the PFC and FMA scores in stroke patients.

CONCLUSION

These study results showed that stroke can cause cerebral haemodynamic changes in the PFC, and the functional imbalance of the left and right PFC in the resting state is correlated with the severity of limb motor dysfunction. Furthermore, we emphasize that the cerebral haemodynamic activity reflected by fNIRS could be used as a reliable neural biomarker for assessing limb motor dysfunction in stroke.

Stress estimation by the prefrontal cortex asymmetry: Study on fNIRS signals

BACKGROUND

Functional near-infrared spectroscopy (fNIRS) is a non-invasive technique frequently used to measure the brain hemodynamic activity in applications to evaluate affective disorders and stress. Using two wavelengths of light, it is possible to monitor relative changes in the concentrations of oxyhemoglobin and deoxyhemoglobin. Besides, the spatial asymmetry in the prefrontal cortex activity has been correlated with the brain response to stressful situations.

METHODS

We measured prefrontal cortex activity with a NIRS multi-distance device during a baseline period, under stressful conditions (e.g., social stress), and after a recovery phase. We calculated a laterality index for the contaminated brain signal and for the brain signal where we removed the influence of extracerebral hemodynamic activity by using a short channel.

RESULTS

There was a significant right lateralization during stress when using the contaminated signals, consistent with previous investigations, but this significant difference disappeared using the corrected signals. Indeed, exploration of the susceptibility to contamination of the different channels showed non-homogeneous spatial patterns, which would hint at detection of stress from extracerebral activity from the forehead.

LIMITATIONS

There was no recovery phase between the social and the arithmetic stressor, a cumulative effect was not considered.

CONCLUSIONS

Extracerebral hemodynamic activity provided insights into the pertinence of short channel corrections in fNIRS studies dealing with emotions. It is important to consider this issue in clinical applications including modern monitoring systems based on fNIRS technique to assess emotional states in affective disorders.

Relationship Between Left-Right Dominancy of Prefrontal Cortex Activity and Heart Rate During Rest and Task Periods: An fNIRS Study

BackgroundFunctional near-infrared spectroscopy (fNIRS) studies demonstrated that regulation of stress response of the autonomic nervous system is mediated by the left-right asymmetry of prefrontal cortex (PFC) activity. However, it is not yet clear whether PFC regulation of stress response is functioning only when the subject was under stress or even at rest without stress. In addition, the temporal responsivity of PFC regulation of stress response is not known.AimThis study aims to investigate the relationship between the left-right asymmetry of PFC activity and heart rate during both resting state and stressful state while performing a working memory task.ApproachTwenty-nine subjects were recruited to rest and conduct 2-back task, during which fNIRS and ECG were measured simultaneously.ResultsWe found weak correlation (r = 0.28, p = 0.137) between laterality index (LI) and heart rate in the task session, but no correlation in rest sessions at a group level. Moreover, weak but significant correlation was found only in the task session for all analysis intervals ranged from 2 s to 1 min.ConclusionIt is suggested that regulation of stress responses was mediated by the left-right asymmetry of PFC activity only when the subject was under stress stimuli and embody stress response did not affect PFC in reverse. This regulation can be observed at an analysis interval of no less than 2 s.

Assessment of dynamic cerebral autoregulation in near-infrared spectroscopy using short channels: A feasibility study in acute ischemic stroke patients

Introduction

In acute ischemic stroke, progressive impairment of cerebral autoregulation (CA) is frequent and associated with unfavorable outcomes. Easy assessment of cerebral blood flow and CA in stroke units bedside tools like near-infrared spectroscopy (NIRS) might improve early detection of CA deterioration. This study aimed to assess dynamic CA with multichannel CW-NIRS in acute ischemic stroke (AIS) patients compared to agematched healthy controls.

Methods

CA reaction was amplified by changes in head of bed position. Long- and short channels were used to monitor systemic artery pressure- and intracranial oscillations simultaneously. Gain and phase shift in spontaneous low- and very low-frequency oscillations (LFO, VLFO) of blood pressure were assessed.

Results

A total of 54 participants, 27 with AIS and 27 age-matched controls were included. Gain was significantly lower in the AIS group in the LFO range (i) when the upper body was steadily elevated to 30. and (ii) after its abrupt elevation to 30°. No other differences were found between groups.

Discussion

This study demonstrates the feasibility of NIRS short channels to measure CA in AIS patients in one single instrument. A lower gain in AIS might indicate decreased CA activity in this pilot study, but further studies investigating the role of NIRS short channels in AIS are needed.

Effect of Exercise Therapy on Stress Response Evaluated by IoMT Monitoring System

The Internet of Medical Things (IoMT) system plays a role in various areas of social activity, including healthcare. Telemetry of cardiovascular function, such as blood pressure and pulse, in daily life is useful in the treatment of cardiovascular disease and stress management. However, until now, brain function monitoring technology has not been installed in the IoMT system.In this study, we used near-infrared spectroscopy (NIRS) installed in the IoMT system to evaluate whether consumers who are not medical experts can measure their own brain function correctly. In addition, the IoMT system was used to assess the long-term effects of physical exercise on physical and mental health.We studied a total of 119 healthy adults recruited from a fitness gym in Koriyama, Japan. After receiving instruction in the usage of the IoMT monitoring system including NIRS, the subjects monitored their physical and mental conditions by themselves when they visited the gym. We evaluated the relations between blood pressure (BP), pulse rate (PR), body weight (BW) and age. In addition, we evaluated the left/right asymmetry of the prefrontal cortex (PFC) at rest and BP. We calculated the laterality index at rest (LIR) for assessment of left/right asymmetry of PFC activity; a positive LIR (>0) indicates right-dominant PFC activity associated with higher stress responses, while a negative LIR (<0) indicates left-dominant PFC activity associated with lower stress responses. We studied 47 out of 119 cases who monitored their physiological conditions before and after physical exercise for 6 months for this study.The results showed that the systolic blood pressure and mean blood pressure (p < 0.05) were significantly reduced after the physical exercise for 6 months; body weight did not change significantly (p > 0.05). In addition, NIRS demonstrated that LIR changed to plus values from minus values after exercise (p < 0.01).These results show that (1) consumers who are not-medical experts can measure their own brain function correctly using NIRS; (2) after long-term physical exercise, systemic blood pressure decreased, associated with modulation of PFC activity (i.e., from right-dominant PFC activity to left-dominant activity), indicating that long-term physical exercises caused relaxation in the brain and the autonomic nervous system.

The effects of age on brain cortical activation and functional connectivity during video game-based finger-to-thumb opposition movement: A functional near-infrared spectroscopy study

OBJECTIVES

This study aims to explore the age-related changes in cerebral cortex activation and functional connectivity (FC) during finger-to-thumb opposition movement based on video games (FTOMBVG).

METHODS

A electronic fingercot was developed for FTOMBVG. The oxygenated hemoglobin concentration (Delta [HbO]) signals, measured by functional near-infrared spectroscopy (fNIRS), were recorded from prefrontal cortex (PFC), motor cortex (MC) and occipital lobe (OL) of two groups of subjects (old and young).

RESULTS

The cognitive region of the old group showed bilateral activation, while the young group only showed unilateral activation. Both groups showed a wide range of bilateral activation in the motor region. The FC between cognitive region and motor region of the old group was enhanced considerably.

CONCLUSION

Changes in cerebral cortex activation and the FC of different brain regions in the old group help explain the decline in cognitive executive and motor control function in the old from the perspective of brain functional structure, and provide a theoretical reference for the prevention of neural diseases caused by aging.

Event-Related NIRS and EEG Analysis for Mental Stress Monitoring

Mental disorders caused by chronic stress are difficult to identify, and colleagues in the work environment may suddenly report symptoms. Social barriers exist including the financial cost of medical services and the lack of a perceived need for treatment even if potential patients have a desire to receive mental healthcare. Self-report inventories such as the Beck Depression Inventory (BDI-II) and State-Trait Anxiety Inventory (STAI) can assess the emotional valence for mental health assessment, but medical expertise may be required for interpretation of the results. Contingency plans for clinical supervision and referral sources are necessary for sufficient mental healthcare using self-report inventories. On the other hand, the laterality index at rest (LIR) has been proposed for evaluation of the mental stress level from near-infrared spectroscopy (NIRS) data in the prefrontal cortex in the resting state. However, the potential for long-term monitoring has not been investigated with sufficient evaluation results. In this study, feature values were extracted from both NIRS and EEG signals each week for 10 weeks in four young participants with an average BDI-II score of 17.7, i.e., indicative of mild depression. Temporal changes in LIR and heart rate (HR) were compared with STAI-Y1 and BDI-II scores. We found cross-correlations between the time series of LIR and STAI-Y1 within one-week delay. In addition, the time series of LIR was also correlated with BDI-II with one-week delay. Importantly, by annotating the larger changes in LIR and HR on daily life events, the changes in LIR and HR were different depending on the type of life event that affected these moods.

A Systematic Review of the Application of Functional Near-Infrared Spectroscopy to the Study of Cerebral Hemodynamics in Healthy Aging

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies have shown that healthy aging is associated with functional brain deterioration that preferentially affects the prefrontal cortex. This article reviews the application of an alternative method, functional near-infrared spectroscopy (fNIRS), to the study of age-related changes in cerebral hemodynamics and factors that influence cerebral hemodynamics in the elderly population. We conducted literature searches in PudMed and PsycINFO, and selected only English original research articles that used fNIRS to study healthy individuals with a mean age of ≥ 55 years. All articles were published in peer-reviewed journals between 1977 and May 2019. We synthesized 114 fNIRS studies examining hemodynamic changes that occurred in the resting state and during the tasks of sensation and perception, motor control, semantic processing, word retrieval, attentional shifting, inhibitory control, memory, and emotion and motivation in healthy older adults. This review, which was not registered in a registry, reveals an age-related reduction in resting-state cerebral oxygenation and connectivity in the prefrontal cortex. It also shows that aging is associated with a reduction in functional hemispheric asymmetry and increased compensatory activity in the frontal lobe across multiple task domains. In addition, this article describes the beneficial effects of healthy lifestyles and the detrimental effects of cardiovascular disease risk factors on brain functioning among nondemented older adults. Limitations of this review include exclusion of gray and non-English literature and lack of meta-analysis. Altogether, the fNIRS literature provides some support for various neurocognitive aging theories derived from task-based PET and fMRI studies. Because fNIRS is relatively motion-tolerant and environmentally unconstrained, it is a promising tool for fostering the development of aging biomarkers and antiaging interventions.

Rightward Shift of Two-Channel NIRS-Defined Prefrontal Cortex Activity during Mental Arithmetic Tasks with Increasing Levels of State Anxiety

This study was aimed at clarifying the effect of different levels of state anxiety caused by mental arithmetic tasks on the anxiety- and/or task performance-related activation of the frontopolar prefrontal cortex (PFC). Twenty-six healthy male subjects performed two sets of mental arithmetic tasks, which consisted of two difficulty levels. Anxiety levels were evaluated subjectively by the State–Trait Anxiety Inventory-Form JYZ (STAI). Near-infrared spectroscopy (NIRS) measurements revealed greater levels of oxyhemoglobin in the frontopolar PFC during experimental tasks. When the subjects were divided into three anxiety groups based on STAI scores, arithmetic task performance was reduced in the moderate and high state anxiety groups compared the low state anxiety group during the experimental task, but not in the control task. Increased frontopolar PFC activity during the experimental task was observed on either side in the moderate anxiety group. The laterality of frontopolar PFC activity in moderate and high state anxiety groups shifted from left to right dominance, independent of task difficulty. Our findings suggested that reduced task performance increased the difficulty of the arithmetic tasks and was involved in the state anxiety-associated rightward lateralization of the frontopolar PFC.

Frontal cerebral oxygenation asymmetry: intersubject variability and dependence on systemic physiology, season, and time of day

Significance: Our study reveals that frontal cerebral oxygenation asymmetry (FCOA), i.e. a difference in the oxygenation between the right and left prefrontal cortex (PFC), is a real phenomenon in healthy human subjects at rest. Aim: To investigate FCOA, we performed a study with 134 healthy right-handed subjects with the systemic physiology augmented functional near infrared spectroscopy (SPA-fNIRS) approach. Approach: Subjects were measured 2 to 4 times on different days resulting in an unprecedented number of 518 single measurements of the absolute values of tissue oxygen saturation (StO 2 ) and total hemoglobin concentration ([tHb]) of the right and left PFC. Measurements were performed with frequency-domain functional near-infrared spectroscopy. In addition, the cardiorespiratory parameters were measured simultaneously. Results: We found that (i) subjects showed an FCOA (higherStO 2 on the right PFC), but not for tHb; (ii) intrasubject variability was excellent for bothStO 2 and tHb, and fair for FCOA; (iii) StO 2 correlated significantly with bloodCO 2 concentration, [tHb] with heart rate, respiration rate (RR), and the pulse-respiration quotient (PRQ), and FCOA with RR and PRQ; (iv) FCOA andStO 2 were dependent on season and time of day, respectively; (v) FCOA was negatively correlated with the room temperature; and (vi) StO 2 and tHb were not correlated with the subjects mood but with their chronotype, whereas FCOA was not dependent on the chronotype. Conclusion: Our study demonstrates that FCOA is real, and it provides unique insights into this remarkable phenomenon.

Development of a Cuff-Less Blood Pressure Monitoring System and Its Application

We present an unobtrusive cuff-less sphygmomanometer based on contact-type and optical pulse sensors for continuous and minimally invasive monitoring of blood pressure (BP). We developed a cuff-less sphygmomanometer that utilizes the pulse arrival time (PAT) to estimate continuous BP. To assess its accuracy, we recruited 10 healthy subjects in whom we carried out BP studies using the cuff-less sphygmomanometer compared with a standard cuff-type device in a stationary sitting patient. Preliminary results showed that the mean difference (MD) of estimated systolic blood pressure and diastolic blood pressure were 0.96 ± 9.6 (mean ± SD) mmHg and 1.14 ± 7.5 mmHg, respectively, compared to the control. The corresponding correlation between the estimated BP values and controls were 0.78 for systolic blood pressure (p < 0.01) and 0.69 for diastolic blood pressure (p < 0.01); thus, there were significant correlations. These results suggest that the developed cuff-less sphygmomanometer has the potential for continuous BP monitoring. Finally, we conducted a preliminary study of simultaneous monitoring of cuff-less BP and near-infrared spectroscopy to evaluate the potential for assessment of autonomic nervous system functions during mental stress tasks.

Right-Left Asymmetry of Prefrontal Cerebral Oxygenation: Does it Depend on Systemic Physiological Activity, Absolute Tissue Oxygenation or Hemoglobin Concentration?

BACKGROUND

We have repeatedly observed a right-left asymmetry (RLA) of prefrontal cerebral oxygenation of subjects during the resting state.

AIM

To clarify if the RLA is a reliably observable phenomenon at the group level and whether it is associated with systemic physiology, absolute tissue oxygen saturation (StO₂) or total hemoglobin concentration ([tHb]).

MATERIAL AND METHODS

StO₂ and [tHb] values at the right and left prefrontal cortex (PFC) were calculated for two 5- min resting phases based on data from 76 single measurements (24 healthy adults, aged 22.0 ± 6.4 years). StO₂ and [tHb] were measured with an ISS OxiplexTS frequency domain near-infrared spectroscopy device. In addition, end-tidal CO₂ (P_ETCO₂), heart rate (HR), respiration rate (RR) and the pulse-respiration quotient (PRQ = HR/RR) were measured and analyzed for the two phases.

RESULTS

On the group level it was found that i) StO₂ was higher at the right compared to the left PFC (for both phases), ii) RLA of StO₂ (∆StO₂ = StO₂ (right)-StO₂ (left) was independent of P_ETCO₂, HR and PRQ, and iii) ∆StO₂ was associated with absolute StO₂ and [tHb] values (positively and negatively, respectively).

DISCUSSION AND CONCLUSION

This study shows that i) RLA of StO₂ at the PFC is a real phenomenon, and that ii) ∆StO₂ at the group level does not depend on P_ETCO₂, HR, RR or PRQ, but on absolute StO₂ and [tHb]. We conclude that the RLA is a real effect, independent of systemic physiology, and most likely reflects genuine properties of the brain, i.e. different activity states of the two hemispheres.

Development of an IoT-Based Monitoring System for Healthcare: A Preliminary Study

We present an IoT-based monitoring system for healthcare that allows for long-term measurements of blood pressure (BP), heart rate (HR), and body weight (BW), as well as near-infrared spectroscopy (NIRS) for measurement of prefrontal cortex (PFC) activity. To verify the applicability of the system, it was set up in a local fitness gym for a preliminary study. A total of 39 subjects, selected from members of the gym, participated in the study. We analyzed the BP, HR, and BW data, collected from the subjects over one half-year. In addition, to assess the degree of mental stress of the subjects, we analysed left-right asymmetry of the PFC activity using the laterality index at rest (LIR) of the NIRS parameter. Results show that the subjects were able to measure their physiological data by themselves when they visited the gym, after being instructed how to perform the measurements. Furthermore, the results also indicate that ordinary people can continuously monitor physiological functions such as brain function in a non-medical facility, such as a fitness gym.

Effects of physical training on brain functional connectivity of methamphetamine dependencies as assessed using functional near-infrared spectroscopy

OBJECTIVE

This study aims to assess the effects of physical training based on the functional near-infrared spectroscopy (fNIRS) and heart rate signals.

METHODS

The oxygenated hemoglobin concentration (Delta [HbO₂]) signals were recorded from the left prefrontal cortex (LPFC), right prefrontal cortex (RPFC), left motor cortex (LMC) and right motor cortex (RMC) of 23 subjects with methamphetamine (METH) dependencies at resting, spinning training and strength training states. The wavelet phase coherence (WPCO) values were calculated in four frequency intervals: I, 0.6-2; II, 0.145-0.6; III, 0.052-0.145; and IV, 0.021-0.052 Hz. During the spinning training and strength training states, heart rate signals were recorded at 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 min, respectively.

RESULTS

After physical training, the brain regions of LPFC, RPFC and LMC showed different degrees of activation in the subjects with METH dependencies (p <  0.05). The WPCO values between the brain regions significantly altered after spinning training and strength training (p <  0.05) in frequency intervals I, II, III and IV.

CONCLUSIONS

The altered WPCO values indicated physical training could affect brain functional connectivity (FC) to a certain extent in the subjects with METH dependencies. These findings provide a method for the assessment of the effects of physical training in FC and will contribute to the development of drug rehabilitation methods in subjects with METH dependencies.

Psychophysiological Responses to Stress Related to Anxiety in Healthy Aging

Abstract. The aim of the study was to explore the effects of situational stress and anxiety in a group of healthy elderly, both in terms of psychophysiological correlates and cognitive performance. Eighteen participants ( Mage = 70 ± 6.3; range 60–85) were assessed for anxiety and were instructed to perform a computerized math task, under both a stressful and a control condition, while near-infrared spectroscopy (NIRS) signal and electrocardiography (ECG) were recorded. NIRS results evidenced an increased activation of right PFC during the entire procedure, even if effect sizes between left and right channels were larger during the experimental condition. The amount of right activation during the stressful condition was positively correlated with anxiety. Response times (RTs) were slower in more anxious than in less anxious individuals, both during the control and stressful conditions. Accuracy was lower in more anxious than in less anxious individuals, only during the stressful condition. Moreover, heart rate (HR) was not modulated by situational stress, nor by anxiety. Overall, the present study suggests that in healthy elderly, anxiety level has a significant impact on cerebral responses, and both on the amount of cognitive resources and the quality of performance in stressful situations.

Cortical and Autonomic Patterns of Emotion Experiencing During a Recall Task

Abstract. Emotions characterized by opposite valences (positive vs. negative) seem to lead to specific patterns of autonomic and cortical activity. For example, according to valence or approach-withdrawal hypotheses, specific emotions lead to an asymmetrical activation of left or right prefrontal cortex (PFC). The aim of the present study was to explore the psychophysiological underpinnings of emotion experiencing using a paradigm with higher ecological validity than is typically accomplished in neuroimaging research. A total of 28 healthy participants were instructed to recall personally-relevant situations from the past that caused positive (happiness) or negative (anger) emotions, during a 2 min silent preparatory phase and a subsequent 3 min verbal phase. A wearable electrocardiographic (ECG) recording system and a portable 2-channel near-infrared spectroscopy (NIRS) device were used to collect heart rate (HR), high frequencies of heart rate variability (HF-HRV), and the hemodynamic responses of prefrontal cortex during the entire procedure. Results showed that during both anger and happiness recall tasks, HR increased and high frequencies of HRV decreased with respect to the baseline. HR and HF-HRV reached, respectively, their highest and lowest points during the verbal phase of anger recall task. NIRS data evidenced a bilateral increase of oxyhemoglobin concentration changes during both anger and happiness recall tasks, which was highest during the verbal phases. However, no lateralization patterns were found. Overall, present results suggest that the experience of negative emotions, if compared with positive ones, is characterized by a combination of reduced parasympathetic activation and/or increased sympathetic activation. Thus, cardiological data provided partial support to autonomic specificity of emotions. However, the recall paradigm did not evidence an asymmetry of PFC activity during the experience of emotions with opposite valences, probably due to the high number of factors impacting prefrontal activity during a recall paradigm.

Effects of Positive and Negative Mood Induction on the Prefrontal Cortex Activity Measured by Near Infrared Spectroscopy

The neurophysiological mechanism of positive versus negative emotions is insufficiently understood. In the present study, we examined the effect of event recall tasks on the prefrontal cortex (PFC) activity using near infrared spectroscopy (NIRS). Nine healthy adults were instructed to recall episodes of their life associated with positive (happiness) and negative (anger) emotion, both silently and verbally. Heart rate (HR) changes were simultaneously measured. NIRS showed an increased oxyhemoglobin (oxy-Hb) in the bilateral PFC during silent and verbal recall of both positive and negative episodes. The changes of oxy-Hb in the bilateral PFC during silent recall of negative episodes were significantly larger than those during silent recall of positive episodes (p < 0.01). There was no difference in average changes of oxy-Hb between silent and verbal recall of negative episodes (p > 0.95), while changes of oxy-Hb during verbal recall of positive episodes were larger than those during silent recall of positive episodes (p < 0.05). Both verbal and silent recall of positive and negative episodes increased HR; however, verbal recall caused larger increases of HR than silent recall (p < 0.01). The present results suggest that recall of negative episodes affect the PFC activity, which plays a key role in cognitive control of emotions, more than positive episodes.

Effects of Antioxidant Supplements (BioPQQ™) on Cerebral Blood Flow and Oxygen Metabolism in the Prefrontal Cortex

Pyrroloquinoline quinone (PQQ) is a quinone compound originally identified in methanol-utilizing bacteria and is a cofactor for redox enzymes. At the Meeting of the International Society on Oxygen Transport to Tissue (ISOTT) 2014, we reported that PQQ disodium salt (BioPQQ™) improved cognitive function in humans, as assessed by the Stroop test. However, the physiological mechanism of PQQ remains unclear. In the present study, we measured regional cerebral blood flow (rCBF) and oxygen metabolism in prefrontal cortex (PFC), before and after administration of PQQ, using time-resolved near-infrared spectroscopy (tNIRS). A total of 20 healthy subjects between 50 and 70 years of age were administered BioPQQ™ (20 mg) or placebo orally once daily for 12 weeks. Hemoglobin (Hb) concentration and absolute tissue oxygen saturation (SO2) in the bilateral PFC were evaluated under resting conditions using tNIRS. We found that baseline concentrations of hemoglobin and total hemoglobin in the right PFC significantly increased after administration of PQQ (p < 0.05). In addition, decreases in SO2 level in the PFC were more pronounced in the PQQ group than in the placebo group (p < 0.05). These results suggest that PQQ causes increased activity in the right PFC associated with increases in rCBF and oxygen metabolism, resulting in enhanced cognitive function.

Functional hemispheric asymmetry in female prefrontal hemodynamics corresponding to changes in auditory sense during pregnancy and child raising

We carried out further research into the prefrontal hemodynamics corresponding to changes in a women's auditory sense during pregnancy and child raising. A total of forty-six volunteers took part in our experiment, and we divided them into several groups in accordance with the progress of their child raising. For the auditory tasks performed by the volunteers, we used two auditory stimulations: the sound of baby crying, and a classical music as a control. Hemodynamic changes at the prefrontal regions were measured using a 2 ch functional near-infrared spectroscopy (fNIRS) along with a 47 ch fNIRS instrument equipped with 3×5 probes (22 ch). Judging the results of the female groups about their prefrontal hemodynamics, there were almost no significant differences across the groups in the dynamics with the music task. However, in the section of the baby crying task, their hemodynamics were regarded as significant compared to the control. Concerning the time scale of the changes in the hemodynamic response to the two tasks, especially in the postnatal group, we took notice of the possibility that higher activations were clearly observed at the right sides of their brains than their left sides. Our experimental results not only demonstrated that postnatal women within one and a half years of their childbearing might have acute ears, but also revealed the hemispheric asymmetry in their prefrontal hemodynamics, as compared to pregnant and nonpregnant volunteers. We inferred that the pregnancy-inducing expression of such women's special capabilities is definitely due to a boost-up of a built-in female disposition, which is destined for expressions of maternal love.

Towards multilevel mental stress assessment using SVM with ECOC: an EEG approach

Mental stress has been identified as one of the major contributing factors that leads to various diseases such as heart attack, depression, and stroke. To avoid this, stress quantification is important for clinical intervention and disease prevention. This study aims to investigate the feasibility of exploiting electroencephalography (EEG) signals to discriminate between different stress levels. We propose a new assessment protocol whereby the stress level is represented by the complexity of mental arithmetic (MA) task for example, at three levels of difficulty, and the stressors are time pressure and negative feedback. Using 18-male subjects, the experimental results showed that there were significant differences in EEG response between the control and stress conditions at different levels of MA task with p values < 0.001. Furthermore, we found a significant reduction in alpha rhythm power from one stress level to another level, p values < 0.05. In comparison, results from self-reporting questionnaire NASA-TLX approach showed no significant differences between stress levels. In addition, we developed a discriminant analysis method based on multiclass support vector machine (SVM) with error-correcting output code (ECOC). Different stress levels were detected with an average classification accuracy of 94.79%. The lateral index (LI) results further showed dominant right prefrontal cortex (PFC) to mental stress (reduced alpha rhythm). The study demonstrated the feasibility of using EEG in classifying multilevel mental stress and reported alpha rhythm power at right prefrontal cortex as a suitable index.

Decreased functional connectivity and disrupted neural network in the prefrontal cortex of affective disorders: A resting-state fNIRS study

BACKGROUND

Affective disorders (AD) have been conceptualized as neural network-level diseases. In this study, we utilized functional near infrared spectroscopy (fNIRS) to investigate the spontaneous hemodynamic activities in the prefrontal cortex (PFC) of the AD patients with or without medications.

METHODS

42 optical channels were applied to cover the superior frontal gyrus (SFG), middle frontal gyrus (MFG), and inferior frontal gyrus (IFG), which constitute one of the most important affective networks of the brain. We performed resting-state measurements on 28 patients who were diagnosed as having AD and 30 healthy controls (HC). Raw fNIRS data were preprocessed with independent component analysis (ICA) and a band-pass filter to remove artifacts and physiological noise.

RESULTS

By systematically analyzing the intra-regional, intrahemispheric, and interhemispheric connectivities based on the spontaneous oscillations of Δ[HbO], our results indicated that patients with AD exhibited significantly reduced intra-regional and symmetrically interhemispheric connectivities in the PFC when compared to HC. More specifically, relative to HC, AD patients showed significantly lower locally functional connectivity in the right IFG, and poor long-distance connectivity between bilateral IFG. In addition, AD patients without medication presented more disrupted cortical organizations in the PFC, and the severity of self-reported symptoms of depression was negatively correlated with the strength of intra-regional and symmetrically interhemispheric connectivity in the PFC.

LIMITATIONS

Regarding the measuring technique, fNIRS has restricted measurement depth and spatial resolution. During the study, the subgroups of AD, such as major depressive disorder, bipolar, comorbidity, or non-comorbidity, dosage of psychotropic drugs, as well as different types of pharmacological responses were not distinguished and systematically compared. Furthermore, due to the limitation of the research design, it was still not very clear how pharmacological treatment affected the resting state cortical organization of the prefrontal lobe, and the degree of the effect in patients with AD.

CONCLUSION

These results strongly supported that RSFC measured by fNIRS could be a useful and powerful way of delineating the neuropathology of AD.

Resting state and personality component (BIS/BAS) predict the brain activity (EEG and fNIRS measure) in response to emotional cues

INTRODUCTION

The present study explored the role of resting state and personality component (BIS/BAS measure) on prefrontal cortical responsiveness to emotional cues. Indeed, we supposed that lateralized resting activity (right vs. left) and approach (BAS) versus avoidance (BIS) attitude may explain the successive emotional processing within the prefrontal cortex (PFC) based on the stimulus valence (positive and negative emotional cues).

METHODS

Hemodynamic (functional near-infrared spectroscopy, fNIRS) and electroencephalographic (EEG) measures were considered. The resting and experimental brain activity were registered when subjects (N = 21) viewed emotional positive versus negative stimuli (International Affective Picture System, IAPS). LIR _eeg and LIR _nirs (lateralized Index Response) during resting state, and LI _eeg and LI _nirs during emotional processing were acquired.

RESULTS

A set of regression analyses was applied to the multiple measures. The predictive effect of resting activity and approach/avoidance dichotomy were elucidated. Indeed, more left/right resting activity (for both LIR _eeg and LIR _nirs) predicted the successive more brain left/right response (LI _eeg and LI _nirs) to emotional cues. Second, significant effects were revealed as a function of valence (increased right response to negative stimuli; increased left response to positive stimuli) during emotion processing. Third, higher BAS values explained an increased left cortical activity in resting state and in experimental condition for positive cues. In contrast, higher BIS values marked an increased right activity in resting state and in experimental condition in response to negative cues.

CONCLUSION

The significance of trait component for both resting and emotional cue processing was discussed at light of the present results.

Temporal Comparison Between NIRS and EEG Signals During a Mental Arithmetic Task Evaluated with Self-Organizing Maps

Simultaneous monitoring of brain activity with near-infrared spectroscopy and electroencephalography allows spatiotemporal reconstruction of the hemodynamic response regarding the concentration changes in oxyhemoglobin and deoxyhemoglobin that are associated with recorded brain activity such as cognitive functions. However, the accuracy of state estimation during mental arithmetic tasks is often different depending on the length of the segment for sampling of NIRS and EEG signals. This study compared the results of a self-organizing map and ANOVA, which were both used to assess the accuracy of state estimation. We conducted an experiment with a mental arithmetic task performed by 10 participants. The lengths of the segment in each time frame for observation of NIRS and EEG signals were compared with the 30-s, 1-min, and 2-min segment lengths. The optimal segment lengths were different for NIRS and EEG signals in the case of classification of feature vectors into the states of performing a mental arithmetic task and being at rest.

Gender and Age Analyses of NIRS/STAI Pearson Correlation Coefficients at Resting State

According to the valence asymmetry hypothesis, the left/right asymmetry of PFC activity is correlated with specific emotional responses to mental stress and personality traits. In a previous study we measured spontaneous oscillation of oxy-Hb concentrations in the bilateral PFC at rest in normal adults employing two-channel portable NIRS and computed the laterality index at rest (LIR). We investigated the Pearson correlation coefficient between the LIR and anxiety levels evaluated by the State-Trait Anxiety Inventory (STAI) test. We found that subjects with right-dominant activity at rest showed higher STAI scores, while those with left dominant oxy-Hb changes at rest showed lower STAI scores such that the Pearson correlation coefficient between LIR and STAI was positive. This study performed Bootstrap analysis on the data and showed the following statistics of the target correlation coefficient: mean=0.4925 and lower confidence limit=0.177 with confidence level 0.05. Using the KS-test, we demonstrated that the correlation did not depend on age, whereas it did depend on gender.

Influence of Pleasant and Unpleasant Auditory Stimuli on Cerebral Blood Flow and Physiological Changes in Normal Subjects

The prefrontal cortex (PFC) plays an important role in emotion and emotional regulation. The valence asymmetry hypothesis, proposes that the left/right asymmetry of the PFC activity is correlated with specific emotional responses to stressors. However, this hypothesis still seems to leave room for clarifying neurophysiological mechanisms. The purpose of the present study was to investigate the effects of stimuli with positive and negative valence sounds (hereafter PS, NS) selected from the International Affective Digitized Sounds-2 on physiological and physiological responses, including PFC activity in normal participants. We studied the effect of both stimuli using 12 normal subjects (mean age 26.8 years) on cerebral blood oxygenation in the bilateral PFC by a multi-channel NIRS, alpha wave appearance rate in theta, alpha, beta by EEG, autonomic nervous function by heart rate, and emotional conditions by the State-Trait Anxiety Inventory (STAI) and the visual analogue scale (VAS). PS was selected over 7.00 and NS were fewer than 3.00 in the Pleasure values. Sounds were recorded during 3 s and reproduced at random using software. Every task session was designed in a block manner: seven rests with Brown Noise (30 s) and six tasks (30 s) blocks. All participants performed each session in random order with eyes closed. A paired Student's t-test was used for comparisons (P<0.05). PFC activity showed increases bilaterally during both stimuli with a greater activation of the left side in PS and a tendency of more activation by NS in the right PFC. Significantly greater alpha wave intensity was obtained in PS. Heart rate tended to show smaller values in PS. The STAI level tended to show smaller values in PS, and a significantly greater VAS score was obtained in PS which indicated 'pleasant'. Despite the limitations of this study such as the low numbers of the subjects, the present study indicated that PS provided pleasant psychological and physiological responses and NS unpleasant responses. The PFC was activated bilaterally, implying a valence effect with the possibility of a dominant side.

Skill acquisition and stress adaptations following laparoscopic surgery training and detraining in novice surgeons

BACKGROUND

Surgical training and practice is stressful, but adaptive changes in the stress circuitry (e.g. perceptual, physiological, hormonal, neural) could support skill development. This work examined skill acquisition and stress adaptations in novice surgeons during laparoscopic surgery (LS) training and detraining.

METHODS

Twelve medical students were assessed for skill performance after 2 h (BASE), 5 h (MID) and 8 h (POST) of LS training in weeks 1-3, and then after 4 weeks of no training (RETEST). The stress outcomes included state anxiety, perceived stress and workload, heart rate (HR), heart rate variability (HRV), and salivary testosterone and cortisol concentrations. Functional near-infrared spectroscopy was used to assess cortical oxygenation change, as a marker of prefrontal cortex (PFC) activity.

RESULTS

Skill performance improved in every session from BASE (p < 0.01), with corresponding decreases in state anxiety, stress, workload, low- and high-frequency HRV in the MID, POST and/or RETEST sessions (p < 0.05). Left and right PFC were symmetrically activated within each testing session (p < 0.01). The stress and workload measures predicted skill performance and changes over time (p < 0.05), with state anxiety, mean HR and the HRV measures also showing some predictive potential (p < 0.10).

CONCLUSIONS

A 3-week LS training programme promoted stress-related adaptations likely to directly, or indirectly, support the acquisition of new surgical skills, and many outcomes were retained after a 4-week period without further LS training. These results have implications for medical training and education (e.g. distributed training for skill development and maintenance, stress resource and management training) and highlighted possible areas for new research (e.g. longitudinal stress and skill profiling).

Resting lateralized activity predicts the cortical response and appraisal of emotions: an fNIRS study

This study explored the effect of lateralized left-right resting brain activity on prefrontal cortical responsiveness to emotional cues and on the explicit appraisal (stimulus evaluation) of emotions based on their valence. Indeed subjective responses to different emotional stimuli should be predicted by brain resting activity and should be lateralized and valence-related (positive vs negative valence). A hemodynamic measure was considered (functional near-infrared spectroscopy). Indeed hemodynamic resting activity and brain response to emotional cues were registered when subjects (N = 19) viewed emotional positive vs negative stimuli (IAPS). Lateralized index response during resting state, LI (lateralized index) during emotional processing and self-assessment manikin rating were considered. Regression analysis showed the significant predictive effect of resting activity (more left or right lateralized) on both brain response and appraisal of emotional cues based on stimuli valence. Moreover, significant effects were found as a function of valence (more right response to negative stimuli; more left response to positive stimuli) during emotion processing. Therefore, resting state may be considered a predictive marker of the successive cortical responsiveness to emotions. The significance of resting condition for emotional behavior was discussed.