Neural representations of skilled movement

The frontal and parietal cortex are intimately involved in the representati on of goal-directed movements, but the crucial neuroanatomical sites are no t well established in humans. In order to identify these sites more precise ly, we studied stroke patients who had the classic syndrome of ideomotor li mb apraxia, which disrupts goal-directed movements, such as writing or brus hing teeth, Patients with and without limb apraxia were identified by asses sing errors imitating gestures and specifying a cut-off for apraxia relativ e to a normal control group, We then used MRI or CT for lesion localization and compared areas of overlap in those patients with and without limb apra xia, Patients with ideomotor limb apraxia had damage lateralized to a left hemispheric network involving the middle frontal gyrus and intraparietal su lcus region. Thus, the results revealed that discrete areas in the left hem isphere of humans are critical for control of complex goal-directed movemen ts.