RECOGNITION MEMORY - NEURONAL SUBSTRATES OF THE JUDGMENT OF PRIOR OCCURRENCE

Recognition memory relies on two processes: (i) identification and (ii ) judgement concerning prior occurrence. A system centred on perirhina l cortex appears to be responsible for judgement of prior occurrence b ased on discrimination of the Familiarity of stimuli or their recency of occurrence; in contrast, a hippocampal system probably supplies inf ormation concerning the episodic, contextual aspects of recognition me mory. This review chiefly concerns the perirhinal system and, in parti cular, neurones that signal the prior occurrence of stimuli by a decre ase in response. Details concerning such decremental responses are giv en and it is argued that such responses in peririnal cortex are adequa te for and central to discrimination of stimulus familiarity and recen cy in a wide range of situations. Information is given of similar type s of neuronal responses in anatomically related brain regions and what may be deduced about the operation of the recognition memory system, The possibility is discussed that the neuronal responses that signal i nformation concerning the recent occurrence of stimuli may contribute to repetition priming as well as recognition memory. Other described c hanges in the activity of individual neurones such as response enhance ments, or sustained (delay) activity may allow solution of specialised forms of recognition memory tasks where relatively short-term working memory is adequate. Implications of the multi-faceted nature of recog nition memory for the interpretation of results are emphasised. Unsolv ed problems and avenues for future experimentation, including determin ing the nature of possible underlying synaptic plastic changes, are di scussed. (C) 1998 Published by Elsevier Science Ltd. All rights reserv ed.