Altered activation in visual cortex: unusual functional magnetic resonance imaging finding in early Parkinson's disease.

Objective Movement dysfunction in Parkinson's disease (PD) is well documented but its cause remains unclear. This study examined whether motor symptoms are caused by sensory impairment, executive dysfunction or other factors. Methods We examined the integration of tactile and motor programmes using functional magnetic resonance imaging (fMRI) in early stage PD patients compared with neurologically normal controls, to investigate neural mechanisms underlying movement dysfunction. Results Twenty-two control participants exhibited activation in an extensive network of cortical regions involved in tactile-motor integration. Decreased activation in somatosensory and motor regions during performance of passive tactile and movement tasks was found in 21 PD patients. The extrastriate visual cortex exhibited greater activation in controls during performance of the tasks. In contrast, greater activation in bilateral prefrontal regions was found in PD patients. Conclusions These results indicate that the extrastriate visual cortex is a multisensory region playing an important role in sensorimotor integration. The findings suggest that PD patients exhibit decreased activation in the extrastriate visual cortex, possibly related to dysfunctional integrative processing, and compensatory activity in the prefrontal cortex.