Corticospinal fibres from the medial aspect of the cerebral hemisphere in the cat. An experimental study with the Nauta method.

Abstract

Using the silver impregnation method of Nauta (1957), corticospinal fibres have been shown to take origin from the cerebral cortex of the medial aspect of the hemisphere in the cat. From the medial wall of the anterior sigmoid gyrus and the anterior cingulate area of the cingulate gyrus corticospinal fibres descend in both lateral funiculi of the cord to sacral cord segments. The fibres in the contralateral lateral funiculus are more numerous than those in the ipsilateral. The ipsilateral component is relatively much greater in the projection from the medial wall of the anterior sigmoid gyrus than in the projection from the primary sensorimotor cortex (Nyberg-Hansen and Brodal 1963). The corticospinal fibres demonstrated in the present study terminate within Rexed's laminae IV–VII as do those from the latter cortical region. The findings are discussed in relation to relevant fibre connections of the supplementary motor area and the anterior cingulate area, and to physiological stimulation and ablation experiments on the medial cerebral cortex. Special emphasis is put on the probability that the supplementary motor area in the cat is localized to the medial wall of the anterior sigmoid gyrus.