Simultaneous Measurement of Hemodynamic and Neuronal Activities Using Near-infrared Spectroscopy and Single-unit Recording

In this study, a custom-manufactured 8-channel continuous-wave near-infrared spectroscopy (CWNIRS) system was used in combination with a single-unit recording device to simultaneously measure hemodynamic and neuronal activities in the somatosensory cortex of rats. Since the single-unit recording reflects the neuronal activities from an extremely localized cortical region, it requires no complex analysis algorithms and, thus, is frequently employed in research including brain-machine interface (BMI) studies. However, the single-unit recording can be conducted only in an invasive way. To test if the NIRS technique has a potential to be utilized in noninvasive BMI studies, we carefully compared the results obtained by using the two techniques. The forepaws of rats were stimulated and the frequency of neuronal firing and the amplitude and slope of the oxy-hemoglobin increase were found to be proportional to the intensity of the peripheral stimulation. We believe that this result may provide some useful insights into the feasibility of using NIRS in noninvasive BMI studies.