Banca de QUALIFICAÇÃO: BRYAN DA COSTA SOUZA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE: BRYAN DA COSTA SOUZA
DATA: 19/12/2014
HORA: 14:00
LOCAL: INSTITUTO DO CÉREBRO
TÍTULO:

Characterization of place cells and their relation with local field potential oscillations in the hippocampal-entorhinal circuitry

 

PALAVRAS-CHAVES:

place cell, place field, theta oscillations, gamma oscillations, hippocampus, entorhinal cortex

PÁGINAS: 60
GRANDE ÁREA: Ciências Biológicas
ÁREA: Fisiologia
RESUMO:

Since the discovery that the hippocampus is involved in memory formation in the 50's, this region and its circuitry have been extensively studied. In particular, many have described the emergence of network oscillations of multiple frequencies depending on behavioral state, which are believed to be important for hippocampal functions. The main inputs to the hippocampus arise from the entorhinal cortex (EC) and form a loop involving the dentate gyrus, CA3 and CA1 hippocampal subfields and then back to EC. Current theories state that CA1, the main output stream of the hippocampus, would interplay inputs from EC and CA3 through network oscillations of different frequencies, namely high gamma (60-100 Hz; HG) and low gamma (30-50 Hz; LG) oscillations, respectively, which tend to be nested in different phases of the theta (5-12 Hz) cycle. Beyond memory, the hippocampus has also been found to play an important role in spatial navigation. In rats and mice, place cells show a close relation between firing rate and the animal position in a restricted area of the environment, the so-called place field. The firing of place cells peaks at the center of the place field and decreases when the animal moves away from it. Besides, place cells also present a spatio-temporal relation with the theta cycle known as phase precession so that they consistently change the theta phase of spiking as the animal traverses the place field. In the present dissertation we use a dataset freely available online to make extensive computational analyses aimed at reproducing classical and new results about the activity of place cells. In particular, we carefully revisit the debate of whether phase precession is due to changes in firing frequency or space alone, and conclude that the phenomenon cannot be explained by either factor independently but by their conjunctive influence. We also perform novel analyses investigating further characteristics of place cells in relation to network oscillations in the hippocampal-entorhinal loop. We find that place cells are differently modulated by theta when they fire inside or outside the place field. Moreover, our results also show that the firing of place cells within the theta cycle is modulated by HG and LG amplitude in both CA1 and EC, matching the cross-frequency coupling results found at the local field potential level.We conclude that place cell firing is embedded in large network states reflected in local field potential oscillations that are believed to have a role in encoding and retrieval and might be seen as a dynamic state rather than a fixed property of the cell.

MEMBROS DA BANCA:
Presidente - 1721223 - ADRIANO BRETANHA LOPES TORT
Interno - 2069422 - DIEGO ANDRES LAPLAGNE
Interno - 1660044 - SIDARTA TOLLENDAL GOMES RIBEIRO