Brain systems and long-term memory.

This paper focuses mainly on those findings derived from lesion studies on the rat which help to identify ensembles of neural structures concerned with the expression of previously learned responses. At the outset, the use of the lesion method in the search for those neurological circuits underlying memory is defended. This is followed by an evaluation of neocortical and subcortical systems in long-term memory. Subsequently, a modest list of tentative functional neural "complexes" involved in the maintenance of certain classes of learned responses is given, based largely upon the author's own research. It is concluded that the key to the understanding of the neurological substrates of long-term memory lies in the identification of those subcortical sites which interact with neocortical sites in the performance of complex learned tasks. The most likely subcortical sites involved in this interaction appear to inhabit the regions of the basal ganglia, limbic midbrain area, and ventral portions of the brainstem reticular formation.