The distribution of the commissural-associational afferents of the dentate gyrus after perforant path lesions in one-day-old rats.

Lesions were made in the entorhinal cortex of one-day-old rats and the distribution of the axons in the dentate gyrus molecular layer studied with the Holmes silver stain when the animals reached adulthood. The commissural-associational projections, normally restricted to the inner dendritic zones, spread evenly throughout the molecular layer ipsilateral to the lesion. This pattern of aberrant growth is markedly different from that which occurs after entorhinal lesions placed in 7-day-old rats. The results are discussed in terms of the factors that dictate the topography of developing afferents.