THE BASAL GANGLIA AND CHUNKING OF ACTION REPERTOIRES

The basal ganglia have been shown to contribute to habit and stimulus- response (S-R) learning. These forms of learning have the property of slow acquisition and, in humans, can occur without conscious awareness . This paper proposes that one aspect of basal ganglia-based learning is the recoding of cortically derived information within the striatum. Modular corticostriatal projection patterns, demonstrated experimenta lly, are viewed as producing recoded templates suitable for the gradua l selection of new input-output relations in cortico-basal ganglia loo ps. Recordings from striatal projection neurons and interneurons show that activity patterns in the striatum are modified gradually during t he course of S-R learning. It is proposed that this recoding within th e striatum can chunk the representations of motor and cognitive action sequences so that they can be implemented as performance units. This scheme generalizes Miller's notion of information chunking to action c ontrol. The formation and the efficient implementation of action chunk s are viewed as being based on predictive signals. It is suggested tha t information chunking provides a mechanism for the acquisition and th e expression of action repertoires that, without such information comp ression would be biologically unwieldy or difficult to implement. The learning and memory functions of the basal ganglia are thus seen as co re features of the basal ganglia's influence on motor and cognitive pa ttern generators. (C) 1998 Academic Press.