Detection of Consciously Controlled Motor Cortical Activation by Near Infrared Spectroscopy (NIRS)

Abstract

Custom headgear was developed and fabricated for the purposes of detecting the hemodynamic response in the motor cortex of the human brain by near infrared spectroscopy (NIRS). We present here, results from this NIRS study. Light in the NIR region was incident upon the human motor cortex in anticipation of observing differences in the absorption curves for recordings of periodic motor activation with respect to periods of rest. Frequency domain NIRS was used to obtain the properties of the NIR signal after the light waves had traversed the brain tissue. Analysis of the intensity of the signal reveals that the absorptive properties of the tissue are altered during periods of activation. T en neurologically healthy individuals each performed both a resting and a motor cortical activation task. We examined the shape of the average time domain curve for each of the two tasks and observe distinct differences; therefore, we anticipate that feature differences between these two curves will consistently discriminate between activation task and baseline responses. In particular, we examined the distribution of the peak-to-peak ranges, inter-peak times, the slopes of the average curves, and the magnitude of the extrema with respect to the mean value. These feature differences may be harnessed to discern a binary signal, thereby demonstrating the hemodynamic signal’s potential as an access pathway enabling individuals with severe motor disability.