[Analysis of electrically evoked response in relation to the central pathway of the cat (3). Current source density analysis in area 17 of cats].
We analyzed current source density and multiple unit activity of area 17 of cats in response to transcorneal electrical stimuli to clarify the localization of the transmembrane current flows contributing to the generation of the electrically evoked response. The results of the current source density analysis were as follows. 1. Current sinks within 20 ms were observed in layers 4 and 6. 2. Current sinks corresponding to N3 (latency 35 ms) were detected in layers 4 and lower 3 and current sources were in the supragranular layers. 3. Current sinks with a latency of more than 40 ms were observed in the supragranular layers. Simultaneous multiple unit activity was present in cases 1 and 2. With increased stimulus frequency or double electrical stimuli, the current sinks corresponding to N3 were decreased. These findings indicate that N1 (latency 9 ms) and N2 (latency 20 ms) reflect near-field potentials generated by geniculocortical afferents in layers 4 and 6, and that N3 is a post-and polysynaptic component. In addition, it appears that dipoles consisting of cell bodies and apical dendrites of pyramidal cells in layer 3 generated by satellite cell in layer 4, play a major role in generating N3.
Shimazu
K
K
Department of Ophthalmology, Nagoya University School of Medicine, Aichi-ken, Japan.
Miyake
Y
Y
Fukatsu
Y
Y
Watanabe
S
S
D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D005074:Evoked Potentials, Visual; D008564:Membrane Potentials; D009435:Synaptic Transmission / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*