Masashi Suda

Frontopolar activation during face-to-face conversation: An in situ study using near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a functional brain imaging technique for monitoring brain activation in a natural setting using near-infrared light, and hence, is considered to have some advantages for studies of brain function during social interactions such as face-to-face conversation compared with functional magnetic resonance imaging and positron emission tomography, which have methodological constraints for studying brain mechanisms underlying social interactions: subjects have to lie down on a bed in a small gantry during examination. The purpose of this study was to validate the possible use of NIRS as a functional brain imaging technique for studying social interactions in a natural setting; therefore, we investigated frontal and temporal lobe activation during face-to-face conversation in healthy subjects in the sitting position. The frontal and superior temporal regions were activated during face-to-face conversation, with higher activity in the speaking segments than in the mute segments during conversation particularly in frontopolar NIRS channels. The magnitude of frontopolar activity negatively correlated with the cooperativeness score of the subjects assessed using the temperament and character inventory. These results demonstrated the successful monitoring of brain function during realistic social interactions using NIRS and interindividual differences in frontopolar activity during conversation in relation to the cooperativeness of an individual.

Subjective feeling of psychological fatigue is related to decreased reactivity in ventrolateral prefrontal cortex

The purpose of this study is to examine the relationship between subjective fatigue and brain function. Twenty-three healthy young volunteers participated in this study. Relationships were investigated between subjective fatigue assessed using visual-analogue scale (VAS) score and sleep duration, and cerebral cortex reactivity during a verbal fluency task by 52-channel near-infrared spectroscopy (NIRS). The VAS score negatively correlated with oxygenated hemoglobin concentration ([oxy-Hb]) increases in the bilateral channels over the regions from the ventrolateral part of the frontal lobe to the upper part of the temporal lobe during the verbal fluency task. Sleep duration in the previous night positively correlated with [oxy-Hb] increases in the bilateral channels over the dorsolateral prefrontal lobe also during the verbal fluency task. No significant correlations between the VAS score and sleep duration in the previous night with [oxy-Hb] increases were found during a control task, the left-finger-tapping task. The subjective feeling of psychological fatigue is related to decreased reactivities in the lateral frontal and superior temporal cortices and is unrelated to sleep duration in the previous night, which is reflected in the reactivity in the dorsolateral prefrontal cortices. These results suggest that transient hypofunction and persistent dysfunction in the lateral prefrontal and temporal lobes are among the brain substrates of fatigue. These also demonstrate the advantage of NIRS for investigating brain function during subjective phenomena such as fatigue because it enables examination in a natural setting.

Dieting tendency and eating behavior problems in eating disorder correlate with right frontotemporal and left orbitofrontal cortex: a near-infrared spectroscopy study.

Frontal lobe dysfunctions have been implicated as one of the pathophysiological bases in eating disorder (ED). Neural substrates of ED have been examined in neuroimaging studies employing symptom-related stimuli, such as food and body-image distortion, but with inconsistent results because of differences in study design, task, and stimulus used. In order to elucidate frontal lobe dysfunction correlates of clinical symptoms in ED, we examined the frontal lobe function during a cognitive task, not a symptom-related task, using near-infrared spectroscopy (NIRS), which is suitable for the functional neuroimaging study of ED because of its complete noninvasiveness and natural measurement setting. Regional hemodynamic changes were monitored during a verbal fluency task (letter version) using a 52-channel NIRS apparatus in 27 female ED patients and 27 matched healthy controls, and their correlations with clinical symptoms assessed using the Eating Attitude Scale (EAT-26) were examined. Regional hemodynamic changes were significantly smaller in the ED group than in the control group in the bilateral orbitofrontal and right frontotemporal regions, and negatively correlated with dieting tendency scores in EAT-26 in the right frontotemporal regions and with the eating restriction and binge eating scores in the left orbitofrontal regions. The clinical symptoms of ED are considered to consist of two components: dieting tendency that correlates with the right frontotemporal cortex and eating behavior problems that correlate with left the orbitofrontal cortex.

Decreased cortical reactivity underlies subjective daytime light sleepiness in healthy subjects: A multichannel near-infrared spectroscopy study

Daytime sleepiness is considered to be one of the main problems in modern society. Of the four aspects of sleepiness, namely, subjective sleepiness, performance decrease, sleep propensity, and arousal decrease, subjective sleepiness is the most difficult to assess. Brain mechanisms underlying subjective light sleepiness in daytime were investigated in healthy subjects using multichannel near-infrared spectroscopy (NIRS), which enables the noninvasive measurement of regional cerebral blood volume (rCBV) changes under natural conditions. Forty right-handed healthy volunteers participated in this study. Relationships were investigated between subjective sleepiness and anxiety, assessed using the Stanford Sleepiness Scale (SSS) and State-Trait Anxiety Inventory (STAI), respectively, and cerebral cortex reactivities assessed as oxygenated and deoxygenated hemoglobin concentration ([oxy-Hb] and [deoxy-Hb], respectively) changes during a verbal fluency task using a 24-channel NIRS machine. SSS score correlated negatively with an [oxy-Hb] increase in the bilateral frontal channels mainly in the middle and last third of the verbal fluency task period. Subjective light daytime sleepiness in healthy subjects is considered to be related to decreased prefrontal reactivities in the later part of cognitive activation.

Autistic Traits and Brain Activation during Face-to-Face Conversations in Typically Developed Adults

Background Autism spectrum disorders (ASD) are characterized by impaired social interaction and communication, restricted interests, and repetitive behaviours. The severity of these characteristics is posited to lie on a continuum that extends into the general population. Brain substrates underlying ASD have been investigated through functional neuroimaging studies using functional magnetic resonance imaging (fMRI). However, fMRI has methodological constraints for studying brain mechanisms during social interactions (for example, noise, lying on a gantry during the procedure, etc.). In this study, we investigated whether variations in autism spectrum traits are associated with changes in patterns of brain activation in typically developed adults. We used near-infrared spectroscopy (NIRS), a recently developed functional neuroimaging technique that uses near-infrared light, to monitor brain activation in a natural setting that is suitable for studying brain functions during social interactions. Methodology We monitored regional cerebral blood volume changes using a 52-channel NIRS apparatus over the prefrontal cortex (PFC) and superior temporal sulcus (STS), 2 areas implicated in social cognition and the pathology of ASD, in 28 typically developed participants (14 male and 14 female) during face-to-face conversations. This task was designed to resemble a realistic social situation. We examined the correlations of these changes with autistic traits assessed using the Autism-Spectrum Quotient (AQ). Principal Findings Both the PFC and STS were significantly activated during face-to-face conversations. AQ scores were negatively correlated with regional cerebral blood volume increases in the left STS during face-to-face conversations, especially in males. Conclusions Our results demonstrate successful monitoring of brain function during realistic social interactions by NIRS as well as lesser brain activation in the left STS during face-to-face conversations in typically developed participants with higher levels of autistic traits.

Stimulus intensity dependence of cerebral blood volume changes in left frontal lobe by low-frequency rTMS to right frontal lobe : A near-infrared spectroscopy study

Repetitive transcranial magnetic stimulation (rTMS) has recently been widely employed for the investigation of brain function and treatment of psychiatric and neurological disorders. Although high and low stimulation frequencies are assumed to activate and deactivate brain function, respectively, the optimal parameters of rTMS for treatment of depression have been determined only on the basis of their clinical efficacy. In this study, we administered a 60-s low-frequency rTMS of three grades low intensities over the right dorsolateral prefrontal cortex (DLPFC) in 10 healthy volunteers, and monitored functional changes of the contralateral DLPFC by near-infrared spectroscopy (NIRS) during and immediately after rTMS. Obtained results demonstrated significant [oxy-Hb] decreases during rTMS, and significant differences in the time courses of [oxy-Hb] changes among three stimulus intensities, that is, [oxy-Hb] decreases were most prominent during the latter half of the stimulation and the first 30s of poststimulation only at 15mm condition (58% intensity). These results suggest that monitoring of brain functional changes due to rTMS using NIRS is useful for elucidating the brain mechanisms underlying the clinical effects of rTMS, and the effects of rTMS over contralateral DLPFC are obtained if the stimulus intensities are more than one-half of the motor thresholds.

Cerebral blood volume changes in patients with eating disorders during word fluency: a preliminary study using multi-channel near infrared spectroscopy

OBJECTIVE: This study investigated the characteristics of cerebral oxygenation changes in eating disorders patients (ED) and normal controls during the cognitive tasks, using a highly time-resolved, and non-invasive instrument. METHOD: Eleven female patients with anorexia nervosa or bulimia nervosa were recruited, and 11 healthy females participated. The relative concentrations of oxy-hemoglobin [o-Hb] and deoxy-hemoglobin [d-Hb] were measured during word fluency task using multichannel near infrared spectroscopy (NIRS). RESULTS: The increases of o-Hb and d-Hb during the task were compared between the groups. ED patients showed lower activation and a gradual increase in o-HB during the task. In the frontal, d-HB concentrations decreased during the task in ED patients. CONCLUSION: These specific patterns of oxygenation changes may indicate less supply and less demand of cerebral blood volume. Bedside measurements of cerebral oxygenation changes using NIRS are useful on understanding of neurophysiological features of ED.

Temporal lobe and inferior frontal gyrus dysfunction in patients with schizophrenia during face-to-face conversation: A near-infrared spectroscopy study

Schizophrenia (SC) is marked by poor social-role performance and social-skill deficits that are well reflected in daily conversation. Although the mechanism underlying these impairments has been investigated by functional neuroimaging, technical limitations have prevented the investigation of brain activation during conversation in typical clinical situations. To fill this research gap, this study investigated and compared frontal and temporal lobe activation in patients with SC during face-to-face conversation. Frontal and temporal lobe activation in 29 patients and 31 normal controls (NC) (n = 60) were measured during 180-s conversation periods by using near-infrared spectroscopy (NIRS). The grand average values of oxyhemoglobin concentration ([oxy-Hb]) changes during task performance were analyzed to determine their correlation with clinical variables and Positive and Negative Syndrome Scale (PANSS) subscores. Compared to NCs, patients with SC exhibited decreased performance in the conversation task and decreased activation in both the temporal lobes and the right inferior frontal gyrus (IFG) during task performance, as indicated by the grand average of [oxy-Hb] changes. The decreased activation in the left temporal lobe was negatively correlated with the PANSS disorganization and negative symptoms subscores and that in the right IFG was negatively correlated with illness duration, PANSS disorganization, and negative symptom subscores. These findings indicate that brain dysfunction in SC during conversation is related to functional deficits in both the temporal lobes and the right IFG and manifests primarily in the form of disorganized thinking and negative symptomatology.

Volume reduction of ventromedial prefrontal cortex in bipolar II patients with rapid cycling: a voxel-based morphometric study.

Although rapid cycling (RC), a course specifier of bipolar I or II disorder, is particularly common among bipolar II patients compared with bipolar I patients, the pathophysiological lines of evidence regarding bipolar II with RC are still limited. In this preliminary study with a cross-sectional design, we examined the regional gray matter (GM) volume in 14 bipolar II patients with RC, 17 patients without RC and 84 healthy controls by whole-brain and region-of-interest (ROI) analysis methods, using magnetic resonance imaging with voxel-based morphometry. Whole-brain analysis in this study revealed that the bipolar II patients with RC showed GM volume reductions in the bilateral hemispheres of the medial orbital prefrontal cortex, ventromedial prefrontal cortex, anterior cingulate, insula and parahippocampus, in the left hemisphere of the inferior temporal cortex and cerebellum, and in the brainstem, compared with the healthy controls. Moreover, ROI analysis focusing on the ventral prefrontal cortex, i.e., Brodmann areas 10, 11 and 47, revealed that the bipolar II patients with RC showed GM volume reduction in the ventromedial prefrontal cortex, compared with the patients without RC. The findings of our pilot study suggest that the ventromedial prefrontal cortex is associated with the generation of RC in bipolar II disorder.

Associations among parenting experiences during childhood and adolescence, hypothalamus‐pituitary‐adrenal axis hypoactivity, and hippocampal gray matter volume reduction in young adults

Recent human studies have indicated that adverse parenting experiences during childhood and adolescence are associated with adulthood hypothalamus‐pituitary‐adrenal (HPA) axis hypoactivity. Chronic HPA axis hypoactivity inhibits hippocampal gray matter (GM) development, as shown by animal studies. However, associations among adverse parenting experiences during childhood and adolescence, HPA axis activity, and brain development, particularly hippocampal development, are insufficiently investigated in humans. In this voxel‐based structural magnetic resonance imaging study, using a cross‐sectional design, we examined the associations among the scores of parental bonding instrument (PBI; a self‐report scale to rate the attitudes of parents during the first 16 years), cortisol response determined by the dexamethasone/corticotropin‐releasing hormone test, and regional or total hippocampal GM volume in forty healthy young adults with the following features: aged between 18 and 35 years, no cortisol hypersecretion in response to the dexamethasone test, no history of traumatic events, or no past or current conditions of significant medical illness or neuropsychiatric disorders. As a result, parental overprotection scores significantly negatively correlated with cortisol response. Additionally, a significant positive association was found between cortisol response and total or regional hippocampal GM volume. No significant association was observed between PBI scores and total or regional hippocampal GM volume. In conclusion, statistical associations were found between parental overprotection during childhood and adolescence and adulthood HPA axis hypoactivity, and between HPA axis hypoactivity and hippocampal GM volume reduction in healthy young adults, but no significant relationship was observed between any PBI scores and adulthood hippocampal GM volume. Hum Brain Mapp 33:2211–2223, 2012.