Responses of ectostriatal neurons during delayed matching-to-sample behavior in pigeons (Columba livia).

We recorded from 71 neurons in the ectostriatum of awake behaving pigeons performing the delayed matching-to-sample task. The ectostriatum is considered to be equivalent to the primate extrastriate cortex. Many of the neurons (n=56, 78.9%) were visually responsive to either or both the red and green stimuli. In addition, a large number of neurons (n=51, 71.8%) exhibited delay activity, that is, a change in activity during the delay period when memory was required compared to the baseline intertrial interval period when memory was not required. We were more likely to encounter a delay neuron when the subjects performed well (>75% correct) compared to when the subjects performed poorly (<75% correct), suggesting that delay activity may carry some functional significance. Finally, the magnitude of the delay activity did not vary across the delay period but remained at a constant elevated or depressed level. Overall, our findings in pigeons are very similar to those reported for primates, and suggest that the pigeon may be an excellent model in which to study the neural mechanisms of visual information processing.