[Abstract Title]. - Society for Neuroscience

296. Learning and Memory: Physiology and Imaging III
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 296.3/TT9
Topic: F.02.i. Learning and memory: Physiology and imaging
Support: NIH Grant MH58847
NIH Grant MH071847
Title: Modulation of correlated activity in primate entorhinal cortex cell pairs for well-learned
associations compared to new associations
Authors: *A. TAMBINI 1 , E. L. HARGREAVES 2 , W. A. SUZUKI 2 ;
1 Ctr. for Neural Sci., 2 New York Univ., New York, NY
Abstract: Several studies have shown that measures of correlated activity across cells can reflect
complex cognitive operations, such as engaging working memory (Jones & Wilson, 2005) or
goal selection and maintenance (Tsujimoto et al., 2008). Here we compared correlated activity in
response to novel vs. very well-learned associations during the performance of a location-scene
association task (Wirth et al., 2003). 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. Reward was followed by
a 2000-3000 ms inter-trial interval period. Animals typically learned 2-4 new location-scene
associations (new trials) together with 4 highly familiar “reference” associations (reference
trials). We analyzed data from 210 entorhinal cortex cell pairs recorded from two monkeys. In
order to determine the correlated activity across cell pairs, we computed the cross-correlation
coefficient for different trial types and task periods for each pair. Since no a priori direction of
spiking between cells was expected, we computed the bias corrected cross-correlation between
cells with a window of ±25 ms. First, we asked if there were any differences in the overall
correlations across the various trial periods for correctly executed new trials compared to
correctly executed reference trials. We found significantly larger correlations in entorhinal cortex
cell pairs in the scene, delay, and inter-trial interval periods of the task for reference trials
compared to new trials (p