Role of the anterior cingulate cortex in the control over behaviour by Pavlovian conditioned stimuli in rats
R.N. Cardinal^1*. J.A. Parkinson², H. Djafari Marbini¹, A.J. Toner¹, T.W. Robbins¹, B.J. Everitt¹
1. Exp Psychol, 2. Anatomy, Univ Cambridge, Cambridge CB2 3EB, United Kingdom

The anterior cingulate cortex (Ant Cing) in the rat has previously been shown to be critical for the acquisition of autoshaping, a measure of Pavlovian conditioning in which animals come to approach a conditioned stimulus (CS+) that predicts food delivery, and not to approach a second, nonpredictive stimulus (CS–). Here we demonstrate that Ant Cing lesions do not impair the acquisition of temporally discriminated approach to a single magazine light CS that predicts food. Lesioned animals were able to respond instrumentally for this CS, now acting as a conditioned reinforcer, and the potentiation of responding by intra-accumbens amphetamine was unaffected. Lesioned rats also acquired a normal freezing response to a discrete CS paired with footshock. However, these same subjects were impaired at autoshaping. A second group of Ant Cing-lesioned rats were tested on a Pavlovian-instrumental transfer task, in which an appetitive CS potentiates ongoing instrumental responding, and no impairment was found.
   These results suggested that the Ant Cing is only critical for the normal expression of appetitive conditioning when multiple stimuli must be discriminated or disambiguated on the basis of their association with reward. To test this hypothesis, a third group of Ant Cing-lesioned rats were trained on a temporally discriminated approach task using two stimuli (a CS+ and a CS–). In support of the disambiguation hypothesis, while sham-operated controls approached the source of food during the CS+ more than during the CS–, Ant Cing-lesioned rats failed to discriminate, approaching equally during both stimuli.

Supported by: MRC (UK)

Key words: autoshaping, discrimination, motivation, appetitive