Preparation for movement in the cat. II. Unit activity in the basal ganglia and thalamus

Of the movement-related units in the globus pallidus and entopeduncular nucleus 30--40% show early (more than 500 msec) onsets of their movement-related activity preceding self-initiated 'elbow'-flexing movements in cats. The medial pericruciate motor cortex and the VL-VA thalamic nuclei display similar distributions of onset times, in contrast to the lateral cruciate cortex where 97% of neurons change their activity much later. The possible significance of the early activity is discussed in relation to the notion of 'response set'. It is suggested that these data support the concept that the basal ganglia participate in the enabling and sequencing of movements rather than in directly causing them to occur.