Shinichi Shiotsuka

Activation of the visual cortex imaged by 24-channel near-infrared spectroscopy

Near-infrared spectroscopy (NIRS) is a noninvasive technique for continuous monitoring of the amounts of total hemoglobin (total-Hb), oxygenated hemoglobin, (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb). The purpose of the present study was to demonstrate the utility of NIRS in functional imaging of the human visual cortex. A new NIRS imaging system enabled measurements from 24 scalp locations covering a 9 cm sq area. Topographic images were obtained from interpolations of the concentration changes between measurement points. Five healthy subjects between 25 and 49 years of age were investigated. After a resting baseline period of 50 s, the subjects were exposed to a visual stimulus for 20 s, followed by a 50 s resting period in a dimly lit, sound attenuating room. The visual stimulus was a circular, black and white, alternating checkerboard. In four of five subjects the visual cortex was the most activated area during visual stimulation. This is the first reported use of a NIRS-imaging system for assessing hemodynamic changes in the human visual cortex. The typical hemodynamic changes expected were observed; the total-Hb and oxy-Hb increased just after the start of stimulation and plateaued after 10 s of the stimulation period.

Activation of visual cortex in REM sleep measured by 24‐channel NIRS imaging

To visualize dreaming brain functions we studied hemodynamic changes in the visual cortex during the transition from non‐rapid eye movement (NREM) to rapid eye movement (REM) sleep, using a 24‐channel Near‐Infrared Spectroscopy (NIRS) imaging method. Results were compared to the activation in visual cortex by visual stimulation during wakefulness. Subjects were four healthy males between 25 and 49 years of age. Five all‐night polysomnographic and NIRS recordings were made. Increases in the oxygenated hemoglobin concentration in visual cortex were observed from nine of 14 REM periods. The activated areas were broader during REM sleep than during visual stimulation. These findings suggest that activation of visual cortex in REM sleep might represent dream‐related brain activity.

Cerebral blood volume in the sleep measured by near‐infrared spectroscopy

Abstract We investigated the relationship between hemodynamic changes in the cortex measured by near‐infrared spectroscopy (NIRS) and the polysomnographic changes during sleep. Four healthy male volunteers participated in the study. Near‐infrared spectroscopy measuring and polysomnographic recordings were done simultaneously during sleep. In many case, oxy‐hemoglobin (oxy‐Hb) decreased and deoxy‐hemoglobin (deoxy‐Hb) increased during the transition from wakefulness to sleep, and oxy‐Hb increased toward deep sleep. Oxy‐Hb and deoxy‐Hb had larger fluctuations during REM sleep than those during non‐REM sleep. During REM sleep, oxy‐Hb often showed a lower level and deoxy‐Hb showed a higher level than those during the preceding and following non‐REM sleep.

Simultaneous recording by NIRS and VEP revealed the dominant response in left primary visual cortex

Introduction Visual evoked potential (VEP) is the response of electrical activity of neurons recorded during 0 (ETH) 300 msec after the stimulation. Functional MRI, PET and NIRS that were recently used for functional brain mapping record the hemodynamic change of the brain which occur a few seconds after the stimulation and continue for several seconds. It is very important to compare these two methodologies for combining conventional EEG studies with new findings in the brain mapping. In the present study simultaneous recording of the response of primary visual field (Vl) was done using conventional VEP and 22-channel NIRS.