Figure 7. Model proposing how the observed activity of ipsiversive-preferring SNr neurons could facilitate internally-specified movements relative to stimulus-guided movements.
(A) Line thickness corresponds to level of activity. Activity preceding stimulus-guided rightward movement. A left SNr neuron is moderately weakly active, providing moderately weak inhibition to the left SC (superior colliculus). A right SNr neuron is moderately strongly active, providing moderately strong inhibition to the right SC. This pattern of activity in the SC moderately promotes rightward movement. (B) Activity preceding internally-specified rightward movement. Compared to A, a left SNr neuron is very weakly active, providing very weak inhibition to the left SC; and a right SNr neuron is very strongly active, providing very strong inhibition to the right SC. This pattern of activity in the SC strongly promotes rightward movement.