B Setlow*, G Schoenbaum & M Gallagher, Soc. Neurosci Abstract (2002)

Considerable evidence suggests that ventral striatum is involved in processing information about cues that predict outcomes with innate biological significance. To investigate encoding of cues predicting appetitive and aversive outcomes, we recorded single-unit neural activity in ventral striatum in rats during acquisition and reversal learning in a go/no-go odor discrimination task. In this task, rats sampled one of two odors on each trial. One odor (positive) signaled delivery of a sucrose solution and the other (negative) a quinine solution. Rats had to learn to withhold responding at a fluid well following the negative odor to avoid the quinine. Neural activity was recorded as the rats learned new discriminations using novel odor cues and during subsequent reversal learning.
Analysis of neural activity during odor sampling revealed that 103/256 neurons (40%) fired selectively to one of the two odors during a period of accurate performance (27 fired more to the positive odor, and 76 fired more to the negative). This selective firing was not evident during early training (suggesting little encoding of odor identity), but developed prior to accurate go/no-go performance (suggesting little relation to motor responses). In addition, 30% of the odor-selective neurons reversed their selectivity when odor-outcome contingencies were reversed. There were no differences in the way in which positive vs. negative odor-selective neurons developed or reversed their selectivity. These data suggest that odor-selective firing reflected learning about both appetitive and aversive outcomes associated with the odors.

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