Figure 2.

Effects of neurotoxic lesions of the orbitofrontal cortex (OFC) on performance in a reinforcer devaluation task. (a) Control rats and rats with bilateral neurotoxic lesions of the OFC were trained to associate a conditioned stimulus (CS, light) with an unconditioned stimulus (US, food). Over four sessions, both lesioned and control rats developed a conditioned responding at the food cup during light presentation. This food-cup response is represented as the percentage of total behavior. The lesion had no effect on the development of the food-cup response. (b) The rats then received presentations of the food item in their home cages followed by illness induced by lithium chloride (LiCl) injection. Some rats in each group received paired presentations of food and illness (black circles and squares); others received unpaired presentations (white circles and squares). Rats that received paired presentations stopped consuming the food item (i.e. the food stimulus was ‘devalued’). Again, no effect of lesion was observed. (c) The following day, the rats were returned to the training environment, and conditioned responses to the light cue were measured. When exposed to the light CS, control rats that had received paired presentations of food and illness (for which the food had been devalued; white bars on the left) showed reduced conditioned responses to the food cup compared with unpaired controls (white bars on the right; asterisk indicates P<0.05). Rats with OFC lesions did not show this decrease in conditioned response as a result of reinforcer devaluation. Lower panels adapted, with permission, from [23] © (1999) the Society for Neuroscience.