Memory in the cortex of the primate.

Memory is viewed as hierarchical and distributed in primary and association areas of cerebral cortex. Different memory neural networks are interconnected at various levels in this hierarchy, sharing neurons and connections. All memory is essentially associative in its generation, structure and retrieval. External and internal stimuli, to which we attend by virtue of their biological relevance or for other reason, can at any time activate ("turn on") the neuronal network to which they belong by previous association. This is the basis of knowledge and remembering. The reverberation in recurrent circuits may keep the network in an active state, that is, serving behavior, attention and consciousness. Monkey neuropsychological and electrophysiological data, and human tomographic (brain metabolism) evidence are presented supporting these concepts.