title: Decreased cortical reactivity underlies subjective daytime light sleepiness in healthy subjects: a multichannel near-infrared spectroscopy study.
abstract: 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.
authors.affiliation: Department of Psychiatry and Human Behavior, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Suda
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Sato
authors.forename: Masaki
authors.initials: M
authors.lastname: Kameyama
authors.forename: Makoto
authors.initials: M
authors.lastname: Ito
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Suto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yamagishi
authors.forename: Toru
authors.initials: T
authors.lastname: Uehara
authors.forename: Masato
authors.initials: M
authors.lastname: Fukuda
authors.forename: Masahiko
authors.initials: M
authors.lastname: Mikuni
mesh_terms: D000328:Adult; D001007:Anxiety / Q000503:physiopathology*; D003071:Cognition / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010108:Oxyhemoglobins / Q000378:metabolism; D017397:Prefrontal Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D012044:Regression Analysis; D012894:Sleep Stages / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D014851:Wakefulness / Q000502:physiology*
chemical_list: D010108:Oxyhemoglobins