title: A NIRS-fMRI investigation of prefrontal cortex activity during a working memory task.
abstract: Near-infrared spectroscopy (NIRS) is commonly used for studying human brain function. However, several studies have shown that superficial hemodynamic changes such as skin blood flow can affect the prefrontal NIRS hemoglobin (Hb) signals. To examine the criterion-related validity of prefrontal NIRS-Hb signals, we focused on the functional signals during a working memory (WM) task and investigated their similarity with blood-oxygen-level-dependent (BOLD) signals simultaneously measured by functional magnetic resonance imaging (fMRI). We also measured the skin blood flow with a laser Doppler flowmeter (LDF) at the same time to examine the effect of superficial hemodynamic changes on the NIRS-Hb signals. Correlation analysis demonstrated that temporal changes in the prefrontal NIRS-Hb signals in the activation area were significantly correlated with the BOLD signals in the gray matter rather than those in the soft tissue or the LDF signals. While care must be taken when comparing the NIRS-Hb signal with the extracranial BOLD or LDF signals, these results suggest that the NIRS-Hb signal mainly reflects hemodynamic changes in the gray matter. Moreover, the amplitudes of the task-related responses of the NIRS-Hb signals were significantly correlated with the BOLD signals in the gray matter across participants, which means participants with a stronger NIRS-Hb response showed a stronger BOLD response. These results thus provide supportive evidence that NIRS can be used to measure hemodynamic signals originating from prefrontal cortex activation.
authors.affiliation: Hitachi, Ltd., Central Research Laboratory, Hatoyama, Saitama 350-0395, Japan. Electronic address: hiroki.sato.ry@hitachi.com.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sato
authors.forename: Noriaki
authors.initials: N
authors.lastname: Yahata
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Funane
authors.forename: Ryu
authors.initials: R
authors.lastname: Takizawa
authors.forename: Takusige
authors.initials: T
authors.lastname: Katura
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Atsumori
authors.forename: Yukika
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Akihide
authors.initials: A
authors.lastname: Kinoshita
authors.forename: Masashi
authors.initials: M
authors.lastname: Kiguchi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Koizumi
authors.forename: Masato
authors.initials: M
authors.lastname: Fukuda
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Kasai
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013647:Task Performance and Analysis
keywords: Blood oxygenation level dependent (BOLD); Finger tapping; Functional magnetic resonance imaging (fMRI); Hemoglobin; Near-infrared spectroscopy (NIRS); Optical topography; Prefrontal cortex; Simultaneous measurement; Working memory