Optical topography during a Go-NoGo task assessed with multi-channel near-infrared spectroscopy.

In this study we investigated the functional brain activation during response inhibition by means of concentration changes in oxygenated [O2Hb] and deoxygenated [HHb] hemoglobin. 9 subjects were measured with multi-channel near-infrared spectroscopy (NIRS) over the left and right lateral prefrontal cortex. The activation task consisted of three blocks of cued Go-NoGo conditions, which were contrasted with three blocks of cued Go conditions. The Go- and Go-NoGo blocks lasted 30 s each, were presented in alternating order, and were preceded by a 30 s resting period. The results clearly show that both conditions induced a brain activation consisting of significant increases of [O2Hb] and decreases of [HHb]. These effects indicate that an active control condition is necessary for the adequate interpretation of the results. Most importantly, we found significantly higher increases of [O2Hb] and decreases of [HHb] during the inhibition phase as compared to the simple motor response in bilateral inferior frontal regions of the brain, which is in accordance with other brain imaging studies. With the introduction of an active control condition in this study, we improved the methodology of a previous investigation. We conclude that multi-channel NIRS is suitable for the functional identification of the inferior prefrontal brain area activated during response inhibition.