Near-infrared Spectroscopy, Motor Cortex, Directional Arm Movements, Optical Imaging, Hemodynamic Response

This study aims at determining arm-movement directions from functional near-infrared spectroscopy (fNIRS) hemodynamic signals in order to decode intentional motor commands, originating in the motor cortices of humans, which could be implemented in neuroprosthetic assistive devices for assisting th e physically disabled. Motor cortical hemodynamic responses were recorded using 64 spatially distributed optrodes from 14 normal subjects during free arm orthogonal movements in the xand y-directions on a horizontal plane. The time course of oxy-(HbO2) and deoxy-hemoglobin (Hb), and of their summation (HbO2 + Hb) and difference (HbO2 – Hb) signals, representing the hemodynamic profiles of total oxygen delivery and ext raction, respectively, were computed for the localized neuronal populations in the motor cort ices underlying the optrodes . Analysis of the above hemodynamic signals revealed that they could be temporally, spatially, or spatiotemporally decoupled, depending on the movement d irection . Thus, by analyzing the spatiotemporal profiles of brain activation we could identify the direction of the orthogonal movements uniquely . Our findings demonstrate that movement direction, a key feature of motor commands, can be reliably extracted in real-time from surface recorded fNIRS signals, and support their viability in future noninvasive assistive devices.