P300 Event Related Potentials from Rat Brain to Cues for Reinforcement and Non-Reinforcement

Abstract

The P300 Event Related Potential (ERP) is a time locked, averaged EEG to task relevant stimuli. Previous research in our laboratory has shown that the P300 ERP in rats is a correlate of the brains recognition of a conditioned reinforcer. More recently, we found that the P300 ERP to a tone that predicted reinforcement was indistinguishable from one that predicted non-reinforcement, linking the P300 ERP to the information in the cue even when the information was predicting the absence of a reinforcer. Here we compared the P300 ERP to the click of a food hopper under two conditions. In one condition (cued reinforcement) a tone signaled a click that was followed by food delivery. In the other condition, the absence of the tone signaled that the click would not be followed by food delivery (non-cued non reinforcement). We found that the P300 ERP to the non-cued non-reinforcement click rapidly disappeared suggesting that the absence of the tone was informative, predicting nonreinforcement and eliminating the response to the click. We are currently gathering data in a condition where the probability of food delivery following a click is 0.5, but there are no cues to provide information about the relevance of the click. Pending completion and analysis, these data will also be reported at DUCURS.