Multiple memory systems

Multiple memory systems describes how memories can be declarative or non-declarative; incentive learning produces one type of non-declarative memory. Patients with bilateral hippocampal damage have declarative memory deficits (amnesia) but intact non-declarative memory; patients with striatal dysfunction, for example, Parkinson’s patients who lose striatal dopamine have impaired incentive learning but intact declarative memory. Rats with lesions of the fornix (hippocampal output pathway), but not lesions of the dorsal striatum, have impaired spatial (declarative) memory; rats with lesions of the dorsal striatum, but not fornix, have impaired stimulus–response memory that relies heavily on incentive learning. These memory systems possibly inhibit one another to control responding: in rats, a group that received fornix lesions and had impaired spatial learning did better on an incentive task; in humans, hippocampus damage was associated with improvement on an incentive learning task and striatal damage was associated with increased involvement of the hippocampus in a route-recognition task.