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Regional properties of dorsal and ventral hippocampus in suppression of intralaminar thalamic unit responses
Author(s) -
Burchell Andrea,
McKenzie J. S.,
Rogers D. K.
Publication year - 1977
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.490030303
Subject(s) - subiculum , entorhinal cortex , hippocampal formation , neuroscience , dentate gyrus , hippocampus , parahippocampal gyrus , thalamus , stimulation , chemistry , psychology , temporal lobe , epilepsy
In chloralose‐anaesthetized, Flaxedil‐paralysed cats, the suppression of extralemniscal thalamic units by dorsal and ventral hippocampus was investigated. Unitary responses to test somatic stimuli, recorded in centrolateral and neighbouring thalamic nuclei, were interacted with conditioning electric stimulation in different regions around the hippocampal arch, including parahippocampal gyrus (entorhinal and retrosplenial areas). Stimulation of dorsal (DHC) and ventral (VHC) hippocampus suppressed roughly equal proportions of responses. However, within each of DHC and VHC, effectiveness depended on the region stimulated. In DHC, fields CA1 and CA3, subiculum (SUB), and retrosplenial area, but not field CA4 or dentate gyrus, usually suppressed extralemniscal units at currents below 1.0 mA. In VHC, the most effective regions were entorhinal cortex, CA3, and CA4 with dentate gryus (FD), while stimulation of CA1 or subiculum was almost ineffective, at currents below 1.0 mA In VHC, the regions were ranked for effectiveness: Entorhinal cortex = CA3> FD > SUB > CA1. No topographic relationship was found between hippocampal region and thalamic loci for unit suppression. Lemniscal‐type unit responses in ventrobasal thalamus were unaffected by stimulation of the hippocampus or parahippocampal gryus. Interruption of the fornix‐fimbria system prevented suppression elicited from CA1 of DHC, or from CA3 but not FD of VHC. It had no effect on suppression elicited from retrosplenial or entorhinal cortex. Hippocampal regional variation of effectiveness in suppressing extralemniscal pathways may contribute to the differential behavioural involvements reported for different hippocampal structures.