ABSTRACT
In discussing the last link of the action and motor memory circuits I first outline the established connections from ventral midbrain and substantia nigra to the striatum and thalamus. Next, I discuss the transmitter systems involved in these pathways and the effect of damage to these systems. I hope to show that at least two systems are involved, one a branch of the action circuit, the other a branch of the motor memory circuit. Since the motor memory circuit is so closely allied to the action circuit, I discuss both in their transit from ventral tegmentum to striatum and thalamus, and try to show where they diverge. Both circuits seem to course closely linked through the substantia nigra and striatum but diverge from globus pallidus to the thalamus.
