ONTOGENETIC ANALYSIS OF SOME EVOKED 



SYNAPTIC ACTIVITIES IN 



SUPERFICIAL NEOCORTICAL NEUROPIL 



DoMiNicK P. Purpura* 



Paul Moore Laboratory of the Department of Neurological Surgery, 



College of Physicians and Surgeons, Columbia University, 



New York 



INTRODUCTION 



The superficial neuropil of neocortex is an elaborately organized sub-pial 

 sheet of axons, dendrites and axodendritic synapses which gives rise to a 

 major portion of the electrical activity recorded from the surface of the 

 brain. Information on its intrinsic synaptic organization may be considered 

 fundamental to an understanding of the different varieties of spontaneous 

 and evoked electrocortical potentials observed under different conditions and 

 the relationship of surface potentials to different patterns of neuronal dis- 

 charges (cf. Purpura, 1959). 



Although some cortical synaptic activities have been analyzed with intra- 

 cellularly located microelectrodes (Branch and Martin, 1958; Buser and 

 Albe-Fessard, 1957; Kandel and Spencer, 1960; Li, 1959; Martin and Branch, 

 1958; Phillips, 1956a, b, 1959; Spencer and Kandel, 1960), the contribution 

 of axodendritic postsynaptic potentials (p.s.p.'s) to these activities has been 

 a matter of conjecture. Apart from a few attempts to analyze cortical dendritic 

 activity with intracellular recording techniques (Li, 1959; Tasaki et al., 1954), 

 most hypotheses concerning the properties of cortical dendrites have evolved, 

 in part, from physiological and pharmacological studies on the nature and 

 origin of evoked superficial negative cortical responses (Chang, 1951; Clare 

 and Bishop, 1955; Eccles, 1951 ; Grundfest, 1958; Purpura, 1959; Purpura and 

 Grundfest, 1956). While it is to be expected that further apphcation and 

 development of microphysiological techniques may permit a more detailed 



* Work of the author, a Sister Elizabeth Kenny Foundation Scholar, was supported 

 in part by a grant (B-I312 C3) from the National Institute of Neurological Diseases and 

 Blindness, and the United Cerebral Palsy Research and Educational Foundation (R-133-60). 

 The data summarized here were obtained in collaboration with Dr. E. M. Housepia, an 

 Parkinson's Disease Foundation Fellow, and Dr. M. W. Carmichael, a Post-Doctoral 

 Fellow in Neuropharmacology, N. I. N. D. B. 



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