How do visual instructions influence the motor system?

The paper distinguishes the use of visual cues to guide reaching and grasping, and the ability to learn to associate arbitrary sensory cues with movements. Using positron emission tomography (PET), we have shown that the arbitrary association of visual cues and movements involves the ventral visual system (prestriate, inferotemporal and ventral prefrontal cortex), the basal ganglia and the dorsal premotor cortex. Using functional magnetic resonance imaging (fMRI), we have shown that the evoked haemodynamic responses in the ventral visual system are time-locked to the presentation of the visual cues, that the response in the motor cortex is locked to the time of response, and that the response in the dorsal premotor cortex shows cuerelated, movement-related and set-related components. Using PET we have shown that there are learning-related changes in activation in both the ventral prestriate cortex and the basal ganglia (globus pallidus) when subjects learn a visuomotor associative task. We argue that the basal ganglia may act as a flexible system for learning the association of sensory cues and movements.