Detecting controlled signals in the human brain by near infrared spectroscopy

We present here results from a preliminary trial of brain activation data collection by near infrared spectroscopy (NIRS). Light in the NIR region was incident upon the human motor cortex in anticipation of observing a detectable change during periods of motor activation with respect to periods of rest. Frequency domain near infrared spectroscopy (NIRS) was used to obtain the amplitude (AC) and intensity (DC) of the NIR signal after it passed through the brain tissue. Analysis of the DC component indicates that the absorptive properties of the tissue are altered during periods of activation. Spectral estimation reveals some frequency components in both amplitude and intensity signals that may serve to discriminate between the periods of activation and the periods of rest. These characteristic differences may be harnessed to control a brain computer interface (BCI).