The effects of bilateral frontal eye-field, posterior parietal or superior collicular lesions on brightness thresholds in the rhesus monkey.

Monkeys were trained to press whichever of two panels showed a small, circular, luminous stimulus. Their brightness thresholds were measured by decreasing the luminance of this stimulus, titrating their performance to the 75 y0 correct level, and averaging over 1000 trials. Both frontal eye-field and superior collicular lesions produced a small but significant rise in threshold when measured l-2 weeks post-operatively. The rise had disappeared by the sixth post-operative week. Brightness thresholds were not affected by posterior parietal lesions.