A bilateral cortico-striate projection

During the course of studies on the projection of the cerebral cortex upon the striatum in the rabbit (Carman, Cowan, and Powell, 1963) and the cat (Webster, 1964) degeneration was seen bilaterally in Nauta preparations of the striatum in some, but not all, animals. For two main reasons this observation was not included in the earlier study. First, because of the difficulty of interpreting any findings of bilateral degeneration in silver preparations, and, particularly as it is well known that the striatum commonly shows pseudo-degeneration, it was imperative to exclude this possibility by the preparation of further material using both the frozen and paraffin Nauta methods. Secondly, because degenera-tion was seen in the contralateral striatum in only a certain number of brains, and it was not until a systematic study of these, and other, brains was undertaken that it became apparent that in all these cases the sensori-motor cortex had been involved to a greater or lesser extent. In view of the obvious significance of this finding for functional studies, and as it represents a striking departure from the generally accepted views concerning the organization of neocortical projection fibres within the telence-phalon, it was felt necessary to establish the validity of the observations as rigorously as possible. Repeated examination of the earlier material and of several brains especially prepared for this purpose has now made it clear not only that a contralateral projection from the cerebral cortex to the striatum exists in the three species which have been studied, but also that it has a localized origin from the region of the sensori-motor cortex and a localized termination within the striatum corresponding closely in its distribution with that to the ipsilateral striatum from the same cortical area. The material used for the present study need not be described in detail as the methods used for the placing of the cortical lesions and the neuro-histological techniques used have been given in the In addition to this material we have prepared several rabbit and rat brains specifically for this investigation, using essentially the same techniques. In all, almost 100 brains of these three species have been independently examined , and evidence for a bilateral projection has been found in 20 animals. The evidence for this projection depends upon the collective findings in several brains, but only a few typical examples will be described in full. The findings in the remaining experiments will …