Discussion
brain injury, hand movements, shoulder movements, ankle movements, hand and shoulder movements
DILATION, CORTEX
This fNIRS study of the hemodynamic response during hand and shoulder movements in healthy subjects confirmed our hypotheses that hand movement is associated with contralateral hemisphere activation in the region of the sensorimotor cortex, and shoulder movement is associated with more medial activation than hand movement. However, in contrast with one of our hypotheses, we did not observe more extensive activation towards the more anterior regions during shoulder movement. These results suggest that fNIRS is a useful alternative to fMRI for the evaluation of proximal limb movement and could be used to investigate cerebral activation in individuals with brain injury.Numerous studies have provided precise information on the neurological control of the hand in animals and humans (Azim and Alstermark Hemodynamic changes have also been described in the ipsilateral supplementary motor cortex (Obrig et al. To our knowledge, only two fNIRS studies compared hand and shoulder movements (Yeo et al. In a more recent study, 20 healthy, right-handed individuals performed similar hand and shoulder tasks to those in our study (Yang et al. Together with the results of those two studies, our results indicate that fNIRS can distinguish between hand and shoulder movements. In all three studies, hand movements were associated with low levels of contralateral activation in the lateral motor regions. The results were less consistent for shoulder movements. Yeo et al. found a marked medial and anterior extension towards the premotor regions, which we did not. Their study does not provide information on right hemisphere activation because the optodes were only placed on the left hemisphere. Unlike our results, which showed exclusive contralateral medial activation, Yang et al. found both contralateral and ipsilateral activation. An fMRI study in 11 healthy subjects studied brain activation during hand, elbow, shoulder, hip and ankle movements (Kocak et al. fMRI and fNIRS are both based on the physiological principles of neurovascular coupling, the process by which active brain regions induce a local increase in blood flow to match their energy demands via the dilation of capillaries and arterioles (Mishra There is a debate as to how to interpret variations in the concentration of each chromophore when the canonical response is not observed. If we take fMRI as the gold standard, HbR would theorically be the most reliable parameter reflecting activation. However, few studies have found strong correlations between HbR concentration and fMRI BOLD signals. HbOThis study has several limitations. The first relates to preprocessing quality. The use of short channels is recommended for the preprocessing of fNIRS data (Yucel et al. 