Banca de DEFESA: JOSÉ HENRIQUE TARGINO DIAS GÓIS

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOSÉ HENRIQUE TARGINO DIAS GÓIS
DATE: 06/12/2019
TIME: 09:00
LOCAL: INSTITUTO DO CEREBRO
TITLE:

On the hippocampal neuronal speed coding

KEY WORDS:

hippocampus, spatial navigation, CA1, neuronal coding, speed cells, place cells, path integration, rate coding, theta

PAGES: 75
BIG AREA: Ciências Biológicas
AREA: Fisiologia
SUMMARY:

Edward Tolman postulated the existence of cognitive maps in the brain to explain the animal capability of spatial navigation. Since then, neuroscience seeks to describe brain components underlying this capability. In the present work, I describe advancements in the characterization of a neural subpopulation engaged in coding the scalar velocity of rat bodies. Upon analyzing an open database, I re-discovered the existence of a velocity code present in the rate of emission of action potentials of neurons in the dorsal hippocampus. I found that this code is independent of theta oscillation frequency (4-12 Hz) and stable over space and time; moreover, it also persists in different contexts. I then classified the neurons as excitatory and inhibitory by the action potential waveform shapes, the rate of emission of action potentials and the temporal inter-dependency of action potential emission between pairs of neurons. This classification revealed that, by using Pearson's correlation as a coding metric, in the square open-field arena only inhibitory neurons coded for speed, even though there was a modulation of the average activity of excitatory neurons. Intriguingly, when checking speed coding in the linear arena, Pearson's correlation made indistinguishable the rate coding between neuronal classes. I then formulated the hypothesis that the apparent speed code of pyramidal neurons in the linear arena is spurious, due to a by-product of their spatial code. To prove this, I simulated artificial neurons that emitted action potentials influenced by the actual animal behavior; the simulated neurons coded either speed or space. The simulation replicated real data, that is, Pearson's correlation detected speed code in speed-influenced simulated cells in both arenas, but in space-influenced simulated cells the speed coding was only present in the linear arena. To solve this ethological interdependency, I adopted a linear-non-linear model and the log-likelihood increase to a fixed mean model as a new coding metric. This analysis disentangled the ethological issue, satisfactorily classifying the simulated neurons and confirming the spurious hypothesis coding and the prevalence of speed code in interneurons. The results of the present work demonstrate that a genuine speed code is present in the dorsal hippocampus in inhibitory interneurons.

 

BANKING MEMBERS:
Presidente - 1721223 - ADRIANO BRETANHA LOPES TORT
Interno - 3086031 - DANIEL YASUMASA TAKAHASHI
Interno - 1698305 - RODRIGO NEVES ROMCY PEREIRA
Externo à Instituição - WERNER TREPTOW - UnB
Externo à Instituição - WILFREDO BLANCO FIGUEROLA - UERN