Investigando ondas teta: características relacionadas à codificação e reconhecimento a curto prazo

• Autor(a) principal: Farias, Yuri Max Araújo Tavares de
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/12002
• topic: Ritmo teta; EEG; Eletroencefalografia; Memória; Theta rhythm; EEG; Electroencephalography; Memory; CNPQ::CIENCIAS HUMANAS::PSICOLOGIA

The theta frequency band has been associated with success in memory encoding and retrieval. Although its effects on memory are widely investigated, electrophysiological characteristics such as limits of frequency bands, increase or decrease of power and their functions, are in debate due to divergence of results between studies and the variety of factors that can influence the mechanisms of encoding and retrieval. In the present study we investigated electrophysiological characteristics in the theta frequency associated to success in encoding and short-term recognition. The study included 18 right-handed graduated students (12 women), aged between 20 and 30 years (mean 22.8). They reported no history of neurological or psychiatric diseases. The experiment consisted of a study phase in which a computerized task of incidental encoding with semantic categorization of images, and a test phase in which new images were added to the ones presented in the previous phase and randomly presented, being classified by the participants as old or new, assigning a confidence level (from 1 to 3) for each response issued. The electrophysiological data related to encoding and retrieval were analyzed separately by comparing hits (recognized) and miss (forgotten). At encoding it was observed a power decrease in pre-stimulus period and power increase in post-stimulus between 2.5 and 4 Hz in the center-parietal region. At the retrieval, a significant power increase in the pre and post-stimulus period was observed in two frequency bands for which it has been found a dissociated spatial location, in the center-parietal region between 2.5 and 3.5 Hz, and in the fronto-temporal and parieto-occipital regions between 4 and 5.5 Hz. The observed results corroborate the relationship between post-stimulus power increase and success in memory encoding and retrieval. A decrease in pre-stimulus power in encoding is associated with non-intentionality in studying, confirming its cognitive preparation function. The frequency bands outside the boundaries of the standard theta band (4-8 Hz) confirm recent observations of functional dissociation between more circumscribed frequency bands. These results suggest that the pre-stimulus activity in encoding represents a process of preparation and that different functions are performed in parallel in different slow frequency bands.