title: Optimizing the general linear model for functional near-infrared spectroscopy: an adaptive hemodynamic response function approach.
abstract: An increasing number of functional near-infrared spectroscopy (fNIRS) studies utilize a general linear model (GLM) approach, which serves as a standard statistical method for functional magnetic resonance imaging (fMRI) data analysis. While fMRI solely measures the blood oxygen level dependent (BOLD) signal, fNIRS measures the changes of oxy-hemoglobin (oxy-Hb) and deoxy-hemoglobin (deoxy-Hb) signals at a temporal resolution severalfold higher. This suggests the necessity of adjusting the temporal parameters of a GLM for fNIRS signals. Thus, we devised a GLM-based method utilizing an adaptive hemodynamic response function (HRF). We sought the optimum temporal parameters to best explain the observed time series data during verbal fluency and naming tasks. The peak delay of the HRF was systematically changed to achieve the best-fit model for the observed oxy- and deoxy-Hb time series data. The optimized peak delay showed different values for each Hb signal and task. When the optimized peak delays were adopted, the deoxy-Hb data yielded comparable activations with similar statistical power and spatial patterns to oxy-Hb data. The adaptive HRF method could suitably explain the behaviors of both Hb parameters during tasks with the different cognitive loads during a time course, and thus would serve as an objective method to fully utilize the temporal structures of all fNIRS data.
authors.affiliation: Jichi Medical University , Center for Development of Advanced Medical Technology, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan ; Chuo University , Applied Cognitive Neuroscience Laboratory, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan.
authors.forename: Minako
authors.initials: M
authors.lastname: Uga
authors.affiliation: Jichi Medical University , Center for Development of Advanced Medical Technology, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan ; Chuo University , Applied Cognitive Neuroscience Laboratory, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan.
authors.forename: Ippeita
authors.initials: I
authors.lastname: Dan
authors.affiliation: Jichi Medical University , Center for Development of Advanced Medical Technology, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan ; Chuo University , Applied Cognitive Neuroscience Laboratory, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Sano
authors.affiliation: Jichi Medical University , Center for Development of Advanced Medical Technology, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan ; Chuo University , Applied Cognitive Neuroscience Laboratory, 1-13-27 Kasuga, Bunkyo, Tokyo 112-8551, Japan.
authors.forename: Haruka
authors.initials: H
authors.lastname: Dan
authors.affiliation: Jichi Medical University , Center for Development of Advanced Medical Technology, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan ; Jichi Medical University , Department of Neurosurgery, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan.
authors.forename: Eiju
authors.initials: E
authors.lastname: Watanabe
keywords: cortical hemodynamics; diffuse optical imaging; optical topography; regression analysis; statistical analysis; statistical parametric mapping