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Electrophysiological characterization of the hippocampal circuitry during the sleep-wake cycle of the rat

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Author(s):
Eduardo Ekman Schenberg
Total Authors: 1
Document type: Doctoral Thesis
Press: São Paulo.
Institution: Universidade de São Paulo (USP). Instituto de Psicologia (IP/SBD)
Defense date:
Examining board members:
Koichi Sameshima; Luiz Roberto Giorgetti de Britto; Marcelo Bussotti Reyes; Sidarta Tollendal Gomes Ribeiro; Luiz Eduardo Ribeiro do Valle
Advisor: Koichi Sameshima
Abstract

The Ammons horn, central structure of the hippocampus, can be subdivided in at least three regions: CA1, CA2 and CA3. While CA1 and CA3 have been extensively studied given the hippocampus involvement in cognitive processes such as memory and pathological ones such as epilepsy, CA2 remains largely ignored. However, this sector contains specific neuroanatomical, biochemical e physiological characteristics, being resistant to induction of plasticity and receiving a specific afference from the supramammillary nucleus in the hypothalamus, involved in the generation/maintenance of the theta rhythm, central oscillations to hippocampal functioning. Therefore, the objective of this study was to characterize electrophysiological patterns of interaction in the three areas of the Ammons horn bilaterally. Results revealed that CA2 has a mean interspike interval larger than CA1 and CA3 during slow wave and REM sleep. During these stages of the sleep-wake cycle, coherence between CA1-CA2 was higher than CA1-CA3 and CA2-CA3 in the three animals evaluated, in three frequency bands: theta (6 to 12 Hz), slow gamma (30 to 50 Hz) and fast gamma (90 to 110 Hz) ipsilaterally. Coherence between contralateral fields was predominant in the theta band and almost zero in other frequencies. These results add to some previous published data showing that CA2 is distinct from the other subfields and that this small region of the Ammons horn may exert important roles in modulating activity in the other hippocampal fields and parahippocampal regions during memory and pathologies such as epilepsy (AU)

FAPESP's process: 06/04351-9 - Characterization of electrophysiological interaction in hippocampal circuitry during learning
Grantee:Eduardo Ekman Schenberg
Support type: Scholarships in Brazil - Doctorate