Hippocampal lesions in pigeons (Columba livia) disrupt reinforced preexposure but not overshadowing or blocking.

Three experiments examined the effects of hippocampal lesions in pigeons on overshadowing, blocking, and a latent inhibition treatment (non-differential reinforced preexposure) using a simultaneous visual discrimination paradigm. The results showed that hippocampal damage did not influence overshadowing (Experiment 1) or blocking (Experiment 2) but did attenuate the retardation in conditioning associated with non-differential reinforced preexposure to to-be-discriminated stimuli (Experiment 3). Hippocampal birds also displayed impaired autoshaping (Experiments 1, 2, and 3). The correspondence between the behavioural effects of avian and mammalian hippocampal lesions is discussed, and the implications of the present pattern of results for avian hippocampal function are considered.