Interhemispheric transfer of visual discrimination in pigeons with supraoptic decussation (DSO) lesions before and after monocular learning.

Pigeons were monocularly trained on a horizontal vs vertical line orientation discrimination. In one group of birds the supraoptic decussation (DSO) was lesioned prior to monocular training, while in another group the lesion was made after the birds learned the task. Both groups were then monocularly trained on the same task with the previously untrained eye. The brains of the birds were examined histologically after the behavioral experiment. In both groups the birds that had damage restricted to the dorsal part of the DSO showed successful interocular transfer and those with completely lesioned DSO did not show the transfer. The results suggest that the tecto-fugal pathway, which connects the two hemispheres via the ventral part of the DSO, is the crucial pathway for interocular transfer, and that memory for a monocularly learned discrimination is unilateral.