Human motor-cortex oxygenation changes induced by cyclic coupled movements of hand and foot

Near-infrared spectroscopy (NIRS) was used to assess human motor-cortex oxygenation changes in response to cyclic coupled movements of hand and foot. Using a highly sensitive NIRS instrument, we showed that it was possible to detect reproducible oxygenation patterns using single cycles (20 s) of easy and difficult association tasks. No significant differences in the time corresponding to the maximal changes in concentration of oxy- and deoxyhemoglobin ([O(2)Hb] and [HHb], respectively) were found during easy and difficult association as well as cycles. Only [O(2)Hb] showed a significantly higher value at the end of the difficult association during the first cycle. No significant differences were found for [O(2)Hb] and [HHb] in the other cycles. We conclude that NIRS is a useful addition to functional magnetic resonance imaging in investigating the time course of cortical activation.