Nucleus cunieformis lesions: Amnestic effects on visual pattern discrimination in the rat

Abstract

Rats were trained on a brightness and pattern discrimination problem following removal of the left posterior half of the neocortex. Electrolytic lesions of the rostral and basolateral portions of the nucleus cuneiformis of the mesencephalic reticular formation on the right side caused serious retention losses of the pattern problem (three animals were unable to relearn), while lesions of similar magnitude to other brainstem areas on the right side did not lead to significant impairments in retention. The animals subjected to transverse lateral midbrain knife-cuts showed a slight but significant loss in retention. These results were interpreted as supporting the view that an occipitoreticular pathway is necessary for the performance of pattern discrimination problems in the albino rat.

Zona incerta: A link between the visual cortical sensory system and the brainstem motor system

“…Finally, the finding that our incertal lesions did not totally abolish the rat's capacity to relearn the pattern discrimination habit raises the possibility that multiple links exist between the visual cortical sensory system and the brainstem motor system. Although this possibility may not be very appealing, it does provide the basis for accounting for the results of earlier experiments suggesting that occipitoreticular (Howze, 1974;Petit & Thompson, 1974;Thompson & Craddock, 1972) and occipitostriate (Livesey & Muter, 1976) pathways may also contribute to pattern discrimination performance in rats .…”

The occipito-striate pathway and visual discrimination performance in the white rat

“…rat. It must be emphasized , however, that occipital efferents to the zona incerta (Thompson & Bachman, 1979) and nucleus cuneiformis of the mesencephalic reticular formation (Petit & Thompson, 1974) may also be implicated in visual discrimination performance. This pattern of results raises the possibility that visually guided behavior may be dependent upon the activation of multiple occipitofugal systems .…”