Hyperstriatal lesions and classical conditioning in the pigeon.

In two experiments, pigeons with bilateral lesions of the hyperstriatum were compared with unoperated control birds and operated control subjects having bilateral lesions of the neostriatum on tasks designed to test two hypotheses of hyperstriatal function. In Experiment 1, hyperstriatal lesions impaired both the acquisition and maintenance of autoshaped responding as well as maintenance responding in response-omission training. In Experiment 2, hyperstriatal birds displayed depressed levels of responding relative to control birds on a classical go-no-go alternation schedule. These results support the view that hyperstriatal selectively disrupt classical conditioning and go against the view that hyperstriatal lesions exaggerate perseverative responding. A surprising aspect of the results was the performance of the operated control subjects that showed better performance in the acquisition of autoshaping and superior differentiation on the go-no-go schedule compared with the unoperated control birds.