Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-12-04T22:45:01Z No. of bitstreams: 1 DanielGomesDeAlmeidaFilho_DISSERT.pdf: 6566932 bytes, checksum: b4e06881e4c037be6166917b5467a5e3 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2015-12-10T19:24:08Z (GMT) No. of bitstreams: 1 DanielGomesDeAlmeidaFilho_DISSERT.pdf: 6566932 bytes, checksum: b4e06881e4c037be6166917b5467a5e3 (MD5) / Made available in DSpace on 2015-12-10T19:24:08Z (GMT). No. of bitstreams: 1 DanielGomesDeAlmeidaFilho_DISSERT.pdf: 6566932 bytes, checksum: b4e06881e4c037be6166917b5467a5e3 (MD5) 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