Electroencephalographic reactivity to unimodal and bimodal visual and proprioceptive demands in sensorimotor integration.

We used electroencephalography to see how the brain deals with altered sensory processing demands in lower extremity movements. In unimodal conditions, sensory processing demands were altered with subjects performing movement to a small or large visual target, or with a small or large weight to modify proprioception. In bimodal conditions, both weight and targets needed to be met. We assessed activity over primary sensorimotor, premotor and parietal areas before and during knee movements. In unimodal conditions, the primary sensorimotor area showed the least sensitivity to the maximally increased sensory demand in both vision and proprioception, while the premotor region was most sensitive to proprioceptive demands, and the parietal region showed greatest sensitivity to visual demands. In bimodal conditions, intermediate levels of sensory processing demand maximally increased activation at premotor and parietal regions. However, when visual and proprioceptive demands were both maximal, activation decreased and was similar to that seen with the lowest level of sensory processing demand. As behavior was consistent across conditions while activation at these regions decreased, we suggest that additional brain areas, possibly high order cognitive and attentional regions, may be required to augment the function of the traditional sensorimotor network in lower extremity movements with increasingly difficult sensory processing demands.