Occlusive behavior of negative-wave direct cortical response (DCR) and single cells in the cortex.

Widely accepted use of the direct cortical response (DCR) for the study of neocortical apical dendrites prompted this study of the response of the surface of hippocampal pallium to direct electrical stimuli in rabbits anesthetized with Dial or Evipal. The hippocampus was directly exposed by radical decortication. The most typical response to direct hippocampal stimulation (DHR) is a monophasic 20–25 msec. negative wave. The DHR is linearly graded throughout the early part of its input-output curve, shows no refractoriness, exhibits long lasting (400 msec.) potentiation of a previously conditioned test response, is rapidly (3–5 sec.) inverted by GABA and is associated with two types of d.c. shifts: a) d.c. shift without concomitant loss of the DHR and b) a variant of spreading hippocampal depression. From these properties the DHR would appear to be quite similar to the DCR. However, different bioelectric generators must be postulated since the hippocampal neural geometry is different from neocortex with respect to the orientation of its predominant neurons.

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Comparison of direct cerebral and cerebellar cortical responses in the cat

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1960.199.4.677 ◽

1960 ◽

Vol 199 (4) ◽

pp. 677-682 ◽

Cited By ~ 7

Author(s):

Albert Rhoton ◽

Sidney Goldring ◽

James L. O'Leary

Keyword(s):

Cerebral Cortex ◽

Synaptic Activity ◽

Aminobutyric Acid ◽

Cortical Surface ◽

Gamma Aminobutyric Acid ◽

Positive Polarity ◽

Negative Wave ◽

Negative Spike ◽

Cortical Responses ◽

Direct Cortical Response

Surface-evoked cerebral and cerebellar responses were compared in 35 cats. Single stimuli and 1-second trains (6 and 20/sec.) were used. Effects of gamma aminobutyric acid (GAB) applied to the cortical surface and of Nembutal and procaine injected intravenously were studied. Response of cerebral cortex to a single shock shows at least four components: initial negative spike, second negative wave, after-positivity, and slow negativity. Cerebellum shows only the initial negative spike and the slow negativity, second negative and after-positivity components being absent. In both cerebrum and cerebellum slow negativity shows summation with serial stimulation. Application of GAB to the cerebellar surface causes replacement of the negative spike by a positive one and a concurrent reduction in amplitude of slow negativity. In cerebral cortex Nembutal produces a striking augmentation of singly or serially evoked slow negativity, but marked amplitude reduction or reversal to positive polarity of the serially evoked primary spikes. By contrast procaine abolishes summed slow negativity of cerebral cortex leaving serial spikes unaffected. In the cerebellum Nembutal and procaine have no effect upon the direct cortical response at dosage sufficient to produce cerebral alterations. Thus synaptic activity signaled by the responses studied appears to be more susceptible to Nembutal and procaine in cerebrum than in cerebellum.

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