Toshimasa Sato

Frontal lobe function in bipolar disorder: a multichannel near-infrared spectroscopy study.

Frontal lobe dysfunction has been implicated as one of the pathophysiological bases of bipolar disorder. Detailed time courses of brain activation in the bipolar disorder group were investigated using multichannel near-infrared spectroscopy (NIRS), a recently developed functional neuroimaging technology with a high time resolution, and were compared with those in the major depression and healthy control groups. Seventeen patients with bipolar disorder, 11 equally depressed patients with major depression, and 17 healthy controls participated in the study. Changes in oxy hemoglobin concentration ([oxy-Hb]) during cognitive and motor tasks were monitored using frontal and temporal probes of two sets of 24-channel NIRS machines. [oxy-Hb] increases in the bipolar disorder group were smaller than those in the healthy control group during the early period of a verbal fluency task, larger than those in the major depression and healthy control groups during the late period of this task, and were smaller than those in the major depression group during a finger-tapping task. Depressive symptoms and antidepressant dosages did not correlate with [oxy-Hb] changes in the two patient groups. Bipolar disorder and major depression were characterized by preserved but delayed and reduced frontal lobe activations, respectively, in the present high-time-resolution study by multichannel NIRS.

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.

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.

Differential relationships between personality and brain function in monetary and goal‐oriented subjective motivation: Multichannel near‐infrared spectroscopy of healthy subjects

Aim:  To examine relationships between personality traits and cerebral cortex reactivity under different motivating conditions.

57. Comparison of prefrontal activation by low-frequency rTMS using two types of coil: A near-infrared spectroscopy study

lished. Our study aimed to investigate the relationships between pain and the stimulus duration when stimulus intensity is just sufficient to obtain the supramaximal stimulation. Fourteen normal subjects were enrolled for this evaluation. Tibial nerve was stimulated at the ankle with two out of three durations of 0.05, 0.2, and 1.0 ms. Six such combinations were tested in a random order, and subjects were asked to report which duration was more painful at each trial. Following two stimulus patterns were examined: pattern 1 was single supramaximal stimulation, and pattern 2 was a train of five maximal stimulations with 1 Hz, respectively. The stimulus duration with 0.2 ms caused minimum pain for both patterns, followed by 0.05 and 1.0 ms. This result indicate shorter duration is not always less painful. Furthermore, if we use 0.05 ms duration, the intensity necessary for supramaximal stimulation may easily exceed 100 mA for a pathological nerve with increased threshold. It is concluded that 0.2 ms duration, widely employed in Japan, is well appropriate.

S24-4 Near-infrared spectroscopy in psychiatry

good agreement between NIRS and WADA test suggesting the clinical application of NIRS in place of WADA test. Monitoring aphasia recovery: We followed 52 cases with aphasia during recovery phase using language task. In 38%, NIRS showed activations in right frontal areas in the initial phase of recovery, which is followed by switching toward the left side activations. 32% showed activations in the cortical areas surrounding left language area throughout the whole course of recovery. Focus diagnosis in epilepsy: 72 cases were monitored by NIRS during epileptic seizures. In 87%, NIRS showed blood volume increase in the focus area. These findings indicated the clinical feasibility of NIRS in the identification of epilepsy focus. Monitoring the hypnotherapy: In 35 cases, NIRS were monitored during hypnotherapy. In every case, when introduction into good hypnotic trance were achieved, NIRS showed blood flow decease in the frontopolar area. On the contrary, when the introduction into trance was failed, no decrease of blood flow was observed in the frontal lobe. These findings suggest that the NIRS can be utilized to detect whether the patient goes into trance or not which has not been able to be attained by EEG.

S52-1 Approval of NIRS as the advanced medical technology in psychiatry

Objective: This lecture reports a study that examined the long-term effects of subthalamic nucleus (STN) deep brain stimulation (DBS) using both clinical and laboratory motor control measures. Methods: Over a five-year time period, changes in the motor section of the Unified Parkinson’s Disease Rating Scale (UPDRS) and bradykinesia and strength at the ankle joint were evaluated on and off stimulation in 8 patients with Parkinson’s disease (PD). Four patients were also studied at the elbow joint. PD patients originally received unilateral STN DBS between years 2001 and 2003 and were re-evaluated after 5 years of longterm STN DBS between years 2006 2008. At baseline and after 5 years, PD patients were tested off treatment (12 hour withdrawal of medication and stimulation) and on stimulation. In each testing condition patients performed ballistic, single degree of freedom ankle dorsiflexion and ankle plantarflexion movements and peak velocity was calculated. Patients also performed maximal voluntary contractions at the ankle joint in both directions, and peak torque was calculated. Results: Results showed increased motor UPDRS scores from baseline to Year 5, but STN DBS was efficacious in reducing them. The main novel finding was that motor control results showed a marked improvement in peak velocity and peak torque over the five year time period even in the off treatment condition. Discussion: The current findings suggest that STN DBS can have beneficial effects on the motor system over the long-term in discrete motor tasks in which maximal neural output is required. These findings are discussed in relation to different models of basal ganglia circuitry.