Probability discrimination learning in hippocampectomized rats

Rats with hippocampal lesions or neocortical lesions and normal rats were trained on a spatial probability discrimination task where one side of a T maze was reinforced on 70% of the trials and the other side on the remaining 30% of the trials. Training was to a criterion of 39 correct trials out of 40 using a noncorrection procedure. There was no difference between the learning rates of normal rats and with neocortical lesions, but the rats with hippocampal lesions learned the discriminiation more rapidly than the other two groups. These results indicated that the hippocampus does not function as a stimulus gating system, but is probably concerned in the selection and rejection of hypothese (central-sets).