Abstract

MACHADO, Birajara Soares; KUNICKI, Ana Carolina Bione; MORYA, Edgard  and  SAMESHIMA, Koichi. Spectral characteristics of the hippocampal LFP during contextual fear conditioning. Einstein (São Paulo) [online]. 2012, vol.10, n.2, pp. 140-144. ISSN 1679-4508.  http://dx.doi.org/10.1590/S1679-45082012000200005.

OBJECTIVE: The hippocampus has an important role in the acquisition and recall of aversive memories. The objective of this study was to investigate the relationship among hippocampal rhythms. METHODS: Microeletrodes arrays were implanted in the hippocampus of Wistar rats. The animals were trained and tested in a contextual fear conditioning task. The training consisted in applying shocks in the legs. The memory test was performed 1 day (recent memory) or 18 days (remote memory) after training. We proposed a measure based on the FFT power spectrum, denominated "delta-theta ratio", to characterize the different behaviors (active exploration and freezing) and the memories types. RESULTS: The delta-theta ratio was able to distinguish recent and remote memories. In this study, the ratio for the 18-day group was smaller than for the 1-day group. Moreover, this measure was useful to distinguish the different behavior states – active exploration and freezing. CONCLUSIONS: The results suggest delta-theta oscillations could reflect the demands on information processing during recent and remote memory recalls.

Keywords : Hippocampus; Memory; Fear [physiology]; Amnesia retrograde.