Abstract
Functional connectivity is defined as spatial correlation between low-frequency cerebral hemodynamic oscillations (< 0.1 Hz) at different regions. Functional connectivity analysis is useful for brain science, so it is desired to conveniently perform the analysis based on NIRS while its signals come partly from the extra-cranial layer. The purpose of this study is to estimate functional connectivity in the frontal cortex from NIRS measurement with two kind of high density multi-distance probes. Ten healthy subjects participated in the experiments after providing written informed consent. Cerebral hemodynamic changes were measured at frontal areas in a resting state by optical topography with source-detector distance (SD) =15, 30mm or 7.5, 30mm. The effective intra-cranial hemodynamic changes were obtained by ICA (Funane's method) for SD=15, 30mm data. Functional connectivity was analyzed based on inter-channel correlation. The results showed that small SD (=7.5mm) components as well as the extra-cranial components corresponding to skin blood flow had high correlation in the whole area, suggested that the connectivity might be overestimated from 30mm components.
