Lateral telencephalic lesions affect visual discriminations in pigeons.

The importance of the lateral telencephalon of the pigeon for visual performance was examined. Lesions in this area markedly impaired both the acquisition and the retention of instrumentally learned hue, intensity and pattern discriminations. Comparable lesions of the thalamofugal visual projection in the dorsoanterior telencephalon did not have an appreciable effect. Laterally lesioned pigeons showed only a minor, non-significant impairment in an instrumental auditory discrimination task. These results generally agree with findings of other authors on domestic chicks but disagree with previous work on pigeons. The visual discrimination performance of laterally lesioned subjects improved gradually over the course of days and weeks without specific experience being necessary, and after 3 months the recovery was virtually complete. The effect of lateral telencephalic lesions is discussed in connection with known visual projections within the avian endbrain and their relationship with other functional systems.