Anterograde degeneration in the superior colliculus following kainic acid and radiofrequency lesions of the macaque pulvinar

Abstract

Several studies have reported behavioral deficits following thermocoagulation of the primate pulvinar. However, these deficits may have resulted from damage to corticotectal fibers as they pass through the pulvinar. To evaluate this possibility and to determine whether kainic acid can be used to destroy pulvinar cells without damaging corticotectal fibers, we compared anterograde degeneration in the superior colliculus following kainic acid and radiofrequency lesions of the pulvinar. Kainic acid injections into the pulvinar produced total loss of neuronal perikarya within the inferior and lateral pulvinar. Four to 7 days following the kainic acid lesions, terminal and fiber degeneration within the superior colliculus was no greater than that produced by control injections of saline. By contrast, thermocoagulation lesions of the inferior and lateral pulvinar produced dense fiber and terminal degeneration throughout the superficial and intermediate layers of the superior colliculus. We conclude that whereas thermocoagulation of the pulvinar severely damages the corticotectal tract, kainic acid lesions spare these fibers of passage. Thus kainic acid lesions should provide an effective tool for studying the functional significance of the pulvinar.