BILATERAL FUNCTIONAL MRI ACTIVATION OF THE BASAL GANGLIA AND MIDDLE TEMPORAL MEDIAL SUPERIOR TEMPORAL MOTION-SENSITIVE AREAS - OPTOKINETIC STIMULATION IN HOMONYMOUS HEMIANOPIA/

Objective: To determine to what extent sensorimotor control is achieve d for each hemisphere separately or interactively during small-field o ptokinetic stimulation in patients with complete homonymous hemianopia . Design: Functional and structural neuroimaging using high-resolution magnetic resonance imaging. Setting: University medical center resear ch facility. Patients: Three patients with complete homonymous hemiano pia after acute infarction of the right posterior cerebral artery. Mai n Outcome Measures: Anatomical location of activated structures during horizontal optokinetic stimulation and T-2-weighted anatomical magnet ic resonance imaging. Results: Occipitotemporal cortical areas (Brodma nn areas 39 and 40) were the only activated cortical structures that s howed statistically significant (P < .01) activation on the affected h emisphere. Of the subcortical areas, activation of thalamic nuclei app eared to be missing on the affected side, whereas the basal ganglia (p utamen, globus pallidus, and caudate nucleus) were bilaterally activat ed. Conclusions: Bilateral activation of the basal ganglia confirms th e concept of the basal ganglia-thalamocortical motor loop and of the e fference copy of oculomotor pathways from each hemisphere. Our finding s suggest 2 possible explanations for the activation of occipitotempor al areas (the human homolog of middle temporal/medial superior tempora l areas) on the infarcted hemisphere: involvement of direct extrastria tal visual pathways or interhemispheric callosal connections between r ight and left middle temporal/medial superior temporal areas.