Ipsilateral afferents to the commissural zone of the fascia dentata, demonstrated in decommissurated rats by silver impregnation

An ipsilateral pathway to the commissural zone of the dentate fascia has been demonstrated in the rat using the Fink‐Heimer silver impregnation method. The pathway arises in one or both of the CA3c and CA4 hippocampal subfields. As lesions of these structures normally will cause degeneration of commissural fibers terminating in the dentate fascia, animals without commissural fibers were provided for this study. This was done by transecting the hippocampal commissures in eight day old rats which were allowed to survive until the adult stage at which time all stainable, degenerating commissural fibers had disappeared. Lesions involving the CA3c/4‐subfields were then made. The resulting degeneration in the commissural zone of the dentate fascia was shown to be of purely ipsilateral origin.