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Updated: Aug 26, 2025
Simultaneous Data Collection of fMRI and fNIRS Measurements Using a Whole-Head Optode Array and Short-Distance Channels
Published on: October 20, 2023
Characterization of forehead blood flow bias on NIRS signals during neural activation with a verbal fluency task
Akitoshi Seiyama1, Tatsuro Miura1, Yuji Sasaki2
1Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan; Creative Design & Data Science Center, Akita International University, Yuwa, Akita 010-1292, Japan.
Abstract:
The major problem of near-infrared spectroscopy (NIRS) for brain activity measurement during verbal fluency task is the overlapping forehead scalp blood flow (FBF) on the target cerebral blood flow (CBF). There could be among-individual differences in the influence of FBF on CBF. We investigated effects of FBF on CBF by comparing signals obtained through a laser Doppler flowmeter (LDF) and NIRS using the modified Beer-Lambert Law (MBLL). Among 25 healthy individuals, 7 participants showed a strong correlation between LDF and NIRS signals (rs >0.500). There were no significant differences according to age or sex. Subsequently, we applied the hemodynamic separation method to the values calculated using the MBLL (Δ[oxy-Hb]M): to separate the concentration of oxygenated hemoglobin in the forehead (Δ[oxy-Hb]F) and cerebral cortex (Δ[oxy-Hb]C). First, we found that the influence of Δ[oxy-Hb]F on Δ[oxy-Hb]C in the high rs group was almost twice as large as that in the low rs group. Second, presence of sex and age differences in the influence of Δ[oxy-Hb]F on Δ[oxy-Hb]C were suggested. Based on the results, we discuss the factors affecting FBF and the resulting variations in NIRS signals.
