[Abstract Title]. - Society for Neuroscience

Title: Further characterization of trial outcome cells in the primate MTL cortex during a
location-scene association task
Authors: *E. L. HARGREAVES, W. A. SUZUKI;
Ctr. for Neural Sci., New York Univ., New York, NY
Abstract: We have previously reported that entorhinal neurons differentiate correct from error
trials during the performance of a location-scene associative learning task (outcome-selective
response; Hargreaves et al., 2007). Here, we ask how stable outcome-selective responses of
entorhinal and parahippocampal cells are by examining their activity during the initial learning
of new location-scene associations and during reversals. In this task, animals initiated each trial
by fixating on a central spot for 500 ms. Four identical targets superimposed on a complex visual
scene were then presented for 500 ms followed by a 700 ms delay period, during which only the
fixation spot and targets remained on the screen. The disappearance of the fixation spot cued the
animal to make an eye movement to one of the four targets, of which only one was rewarded. On
correct trials, animals were given a random number of juice reward drops (2-4) 43 ms after a
correct response that lasted an average of 900 ms followed by a 1000 ms inter-trial-interval (ITI).
Following an error trial, no juice was given and the trial progressed immediately to a 2000 ms
ITI. Animals typically learned 2-4 new location-scene associations and for a subset of the
sessions, 2 of the location-scene associations were reversed after the initial learning. We
analyzed 116 units from the entorhinal and parahippocampal cortices of two monkeys. We found
that the activity of 67% (78/116) of the cells were significantly responsive during either the
reward, ITI or both periods relative to baseline (t; p