Role of the anterior cingulate cortex in the control over behavior by Pavlovian conditioned stimuli in rats.

To investigate the contribution of the anterior cingulate cortex (ACC) to stimulus–reward learning, rats with lesions of peri- and postgenual ACC were tested on a variety of Pavlovian conditioning tasks. Lesioned rats learned to approach a food alcove during a stimulus predicting food, and responded normally for conditioned reinforcement. They also exhibited normal conditioned freezing and Pavlovian– instrumental transfer, yet were impaired at autoshaping. To resolve this apparent discrepancy, a further task was developed in which approach to the food alcove was under the control of 2 stimuli, only 1 of which was followed by reward. Lesioned rats were impaired, approaching during both stimuli. It is suggested that the ACC is not critical for stimulus–reward learning per se, but is required to discriminate multiple stimuli on the basis of their association with reward. The rodent anterior cingulate cortex (ACC) has been extensively implicated in stimulus–reinforcer learning, in aversive and appetitive situations. The ACC receives nociceptive information and is involved in the coordination of autonomic responses (Fisk & Wyss, 1997; Hsu & Shyu, 1997; Neafsey, Terreberry, Hurley, Ruit, & Frysztak, 1993); early studies found that aspirative lesions of the ACC attenuated classically conditioned bradycardia in the rabbit (Buchanan & Powell, 1982). The rabbit ACC is also involved in active avoidance behavior. Using a task in which rabbits must learn to step in response to a tone (conditioned stimulus, CS) to avoid a shock, while ignoring a different tone (CS–), Gabriel et al. have shown electrophysiologically that discriminated neuronal activity (discharge to the CS but not the CS–) occurs within the ACC early in avoidance training (Gabriel, Foster, Orona, Saltwick, & Stanton, 1980; Gabriel & Orona, 1982; Gabriel, Orona, Foster, & Lambert, 1980; Gabriel, Vogt, Kubota, Poremba, & Kang, 1991). Lesions of the ACC impair the avoidance response (Gabriel, 1993; Gabriel, Kubota, Sparenborg, Straube, & Vogt, 1991), attributed to the loss of associative infor