S. Sobotka et Jl. Ringo, INVESTIGATION OF LONG-TERM RECOGNITION AND ASSOCIATION MEMORY IN UNITRESPONSES FROM INFEROTEMPORAL CORTEX, Experimental Brain Research, 96(1), 1993, pp. 28-38
We investigated recognition and association memory in the responses of
single units isolated in the inferior temporal cortex of a macaque wh
ile it performed a visual discrimination task. The unit responses show
ed significant recognition memory (a decreased response upon image rep
etition). Furthermore, a recognition memory appeared to be a permanent
feature in these units. Such memory was evident in responses recorded
at least 1 h after the most recent presentations of the more familiar
images and may have been built up over the months of training. For th
ese cells, the shorter-term recognition memory (seconds) and the longe
r-term recognition memory (hour plus) were significantly correlated (0
.68). In these same cells associative memory was investigated with ten
abstract images which had been randomly and permanently paired. The m
onkey had been taught to discriminate these five pairs from other simi
lar pairs of images. Neither the spike count nor temporal response sha
pe (as determined by a principal-components analysis) showed increased
similarity for the images that had been paired. The cells that had bo
th short-term and long-term recognition memory had responses to previo
usly paired stimuli that were no more similar than expected by chance.