A comparison of levodopa treatment and task demands on visual evoked potentials in hemi-Parkinsonism

In patients with hemi-Parkinsonism the amplitude of visual evoked potential (EP) components was relatively reduced over the hemisphere contralateral to Parkinsonian symptomatology. Chronic levodopa treatment tended to reverse this lateral asymmetry. Before levodopa treatment, participation in a simple attentional task brought about similar EP changes. After levodopa treatment, only patients with left symptomatology responded to the attention task with an enlargement of EP components, largely in the noninvolved hemisphere. These findings suggest that task demands cause changes in the sensory system which are similar to those contributing to “paradoxical kinesia.”