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Previous issue date: 2014-07-22 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Hebb prop?s que sinapses entre neur?nios que disparam de forma s?ncrona s?o fortalecidas formando assembleias de c?lulas e sequ?ncias de fase. A primeira, numa escala menor, ? um conjunto de c?lulas sincronizadas, que funcionam de forma transit?ria como um sistema fechado de processamento; a ?ltima, numa escala maior, corresponde ? ativa??o sequencial de assembleias de c?lulas neuronais capazes de representar percep??es e comportamentos. Atualmente, o registro de grandes popula??es neuronais permite a detec??o simult?nea de diversas assembleias neuronais. No ?mbito da teoria de Hebb, o pr?ximo passo l?gico ? a an?lise das sequ?ncias de fase. Neste trabalho investigamos seq??ncias de fase como padr?es de ativa??es consecutivas de assembleias, analisando a rela??o entre comportamento animal e atributos de grafos de assembleias. Foram estudados trens de disparo neuronal registrados no hipocampo e neoc?rtex de 5 ratos adultos, antes, durante e depois da explora??o de novos objetos (per?odos experimentais). Para definir um grafo de assembleia, cada assembleia correspondeu a um n?, e cada aresta correspondeu ? sequ?ncia temporal de ativa??o de n?s consecutivos. A soma da ativa??o de todas as assembleias foi proporcional ? taxa de disparo, mas a atividade de assembleias individuais n?o. O repert?rio de assembleias permaneceu est?vel ao longo dos per?odos experimentais, indicando que a experi?ncia com novos objetos n?o criou novas assembleias no rato adulto. Os atributos de grafos das assembleia, por outro lado, variaram significativamente entre os estados comportamentais e per?odos experimentais e foram distintos o suficiente para permitir a classifica??o autom?tica dos per?odos experimentais (classificador Naive Bayes; AUROCsm?ximas variaram entre 0,55 a 0,99) e estados comportamentais (vig?lia, sono de ondas lentas e sono de movimento r?pido dos olhos; AUROCs m?ximas variaram entre 0,64 e 0,98). Nossos achados refor?am a teoria Hebbiana de que as assembleias neuronais correspondem a estruturas primitivas de representa??o, quase inalteradas na maturidade, enquanto as seq??ncias de fase s?o inst?veis entre os estados comportamentais e mudam ap?s novas experi?ncias. Os resultados s?o compat?veis com um papel das sequ?ncias de fase no comportamento e cogni??o. / Hebb proposed that synapses between neurons that fire synchronously
are strengthened, forming cell assemblies and phase sequences. The former,
on a shorter scale, are ensembles of synchronized cells that function transiently
as a closed processing system; the latter, on a larger scale, correspond to the
sequential activation of cell assemblies able to represent percepts and
behaviors. Nowadays, the recording of large neuronal populations allows for the
detection of multiple cell assemblies. Within Hebb?s theory, the next logical step
is the analysis of phase sequences. Here we detected phase sequences as
consecutive assembly activation patterns, and then analyzed their graph
attributes in relation to behavior. We investigated action potentials recorded
from the adult rat hippocampus and neocortex before, during and after novel
object exploration (experimental periods). Within assembly graphs, each
assembly corresponded to a node, and each edge corresponded to the
temporal sequence of consecutive node activations. The sum of all assembly
activations was proportional to firing rates, but the activity of individual
assemblies was not. Assembly repertoire was stable across experimental
periods, suggesting that novel experience does not create new assemblies in
the adult rat. Assembly graph attributes, on the other hand, varied significantly
across behavioral states and experimental periods, and were separable enough
to correctly classify experimental periods (Na?ve Bayes classifier; maximum
AUROCs ranging from 0.55 to 0.99) and behavioral states (waking, slow wave
sleep, and rapid eye movement sleep; maximum AUROCs ranging from 0.64 to
0.98). Our findings agree with Hebb?s view that neuronal assemblies
correspond to primitive building blocks of representation, nearly unchanged in 10
the adult, while phase sequences are labile across behavioral states and
change after novel experience. The results are compatible with a role for phase
sequences in behavior and cognition
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19446 |
| Date | 22 July 2014 |
| Creators | Almeida Filho, Daniel Gomes de |
| Contributors | 50591797100, http://lattes.cnpq.br/0649912135067700, Maciel, Sergio Tulio Neuenschwander, 45548927604, http://lattes.cnpq.br/9217956361436464, Laplagne, Diego Andres, 70638083460, http://lattes.cnpq.br/0293416967746987, Galves, Jefferson Antonio, 22042482820, http://lattes.cnpq.br/5430021088108855, Miranda, Jos? Garcia Vivas, Ribeiro, Sidarta Tollendal Gomes |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM NEUROCI?NCIAS, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | Portuguese |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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