I am very grateful to Dr. Mark Rosenzweig and Dr. Marion C. Diamond for giving me the opportunity to pursue this study and for providing the facilities for experimental work related to their own project. To Dr. T. D. McCown I owe a particular debt for his understanding, encouragement, and support in undertaking neurological studies. Finally, I am very much in debt to T. D. Lanagan for his many helpful suggestions and comments. Naturally, I am to be held entirely responsible for the views put forth in this paper.
Much of the data on which this paper is based were collected while under a NIMH fellowship (Predoctoral) MPM-17, 171-C1 1961–62 while at the Department of Anthropology, University of California, Berkeley. The experimental work on dendritic branching was carried out under a Postdoctoral NIMH fellowship, 1-F2-MH-17, 171–01, 1964, Department of Anatomy, University of California, Berkeley.