Dopamine agonists reorient visual exploration away from the neglected hemispace

Objective: To study the effects of bromocriptine, a dopamine agonist, on visual search. Background: The anatomic substrate of spatial attention takes the form of a distributed network with interconnected cortical (frontal, parietal, and cingulate) and subcortical (striatal and thalamic) components. Dopamine appears to exert a modulatory effect on the function of this network. Methods: Seven consecutive right-handed subjects with right-sided cerebral lesions were studied using a computerized target search paradigm. Eye movements were recorded. Results: Bromocriptine caused the subjects to spend more time exploring the ipsilesional hemispace and therefore increased the relative neglect of the contralesional left hemispace. However, target detection accuracy did not change. Bromocriptine thus had a differential impact on the exploratory-motor versus sensory-perceptual components of directed attention. Conclusions: Our results show that bromocriptine may worsen some aspects of hemispatial neglect in patients with lesions that include the postsynaptic components of ascending dopaminergic pathways.