title: Vector-based phase classification of initial dips during word listening using near-infrared spectroscopy.
abstract: This study examined the classification of initial dips during passive listening to single words by analysis of vectors of deoxyHb and oxyHb measurements simultaneously derived from near-infrared spectroscopy. The initial dip response during a single-word 1.5-s task in 13 healthy participants was significant only in the language area, which includes the left posterior superior temporal gyrus and angular gyrus. Event-related vectors of responses to comprehended words moved significantly into phase 4, a dip phase, whereas vectors of responses to unknown words moved into a nondip phase (P<0.05). The same results were reproduced after previously unknown words were learnt by the participants. Among the five dip phases, reflecting variations in transient oxygen metabolic regulation during a task, the frequency of occurrence of hypoxic-ischemic initial dips (decreased oxyHb) was around three times that of the canonical dip (increased deoxyHb and oxyHb). Phase classification of event-related vectors enhances the slight amount of oxygen exchange that occurs in word recognition, which has been difficult to detect because of its small amplitude.
authors.affiliation: Department of Brain Environmental Research, KATOBRAIN Co. Ltd, Tokyo, Japan.
authors.forename: Kayoko
authors.initials: K
authors.lastname: Yoshino
authors.forename: Toshinori
authors.initials: T
authors.lastname: Kato
mesh_terms: D000161:Acoustic Stimulation / Q000145:classification* / Q000379:methods*; D000328:Adult; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping / Q000145:classification / Q000379:methods; D032882:Comprehension / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D019265:Spectroscopy, Near-Infrared / Q000145:classification* / Q000379:methods*; D013702:Temporal Lobe / Q000502:physiology*; D055815:Young Adult