Psychophysical study of the chromatic discrimination in pigeons after lesions of thalamic nuclei Rotundus (RT) and Geniculatus Lateralis ventralis (GLv)

The discrimination threshold at 510 and 640 nm has been measured before and after the bilateral lesion with ka?nic acid of two main thalamic structures: the nucleus rotundus (Rt) and the nucleus geniculatus lateralis ventralis (GLv). When the lesion destroys the GLv and the lower part of the Rt, thresholds increase followed by a progressive recuperation. In contrast, when the Rt lesion is complete, and whether the GLv is touched or not, the threshold increase is both higher and does not come down to the pre-operatory levels even after 15 post-operatory sessions.