Whereas numerous findings support a distinction between episodic and semantic memory, it is now widely acknowledged that these two forms of memory interact during both encoding and retrieval. The precise nature of this interaction, however, remains poorly understood. To examine the role of semantic organization during episodic encoding and retrieval, we recorded intracranial encephalographic signals as 69 neurosurgical patients studied and subsequently recalled categorized and unrelated word lists. Applying multivariate classifiers to neural recordings, we were able to reliably predict encoding success, retrieval success, and temporal and categorical clustering during recall. By assessing how these classifiers generalized across list types, we identified specific retrieval processes that predicted recall of categorized lists and distinguished between recall transitions within and between category clusters. These results particularly implicate retrieval (rather than encoding) processes in the categorical organization of episodic memories.

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Agradeço à família pelas oportunidades e pelo apoio financeiro e emocional, em especial minha mãe, Ligia Maria Pena Borges, meu pai, Marcio Nunes Cambraia e meus irmãos Maria Claudia e Marcio Rodrigo. À minha orientadora, Prof. Dra. Elenice Seixas Hanna que tem me apoiado desde a graduação. Também a todos os membros do grupo de pesquisa, em especial à prof. Raquel Maria de Melo, às alunas Tereza Brito e Laís Calil que me ajudaram muito na fase de coleta, e à amiga Nagi Hanna Salm Costa. Agradeço o apoio financeiro recebido pelo CNPq. Aos amigos do Taekwondo, em especial Mestre Vinicius Avelino por ter cedido o espaço físico da academia para a realização da coleta de dados. Ao professor João Gilberto Fernandes pelo ótimo trabalho. Ao professor Roberto Brandão por tornar a prática de artes marciais tão reforçadora. Aos membros da banca pela disponibilidade e pelas críticas fundamentais para o aprimoramento deste trabalho.Aos participantes da pesquisa pela importante contribuição à ciência e por estarem dispostos a se deslocar até a academia quantas vezes fosse necessário.

We investigated how base rates affect temporal discrimination. In a temporal bisection task, pigeons learned to choose one key after a short sample and another key after a long sample. When presented with a range of intermediate samples they produced a psychometric function characterized by a bias and a scale parameter. When one of the trained samples was more frequent than the other, only the location parameter changed, with the pigeons biasing their choices toward the key associated with the most frequent sample. We then reproduced the bisection task in a long operant chamber, with choice keys far apart, and tracked the pigeons' motion patterns during the sample. Pigeons learned to approach the short key following sample onset, wait on the "short side" for a few seconds, and then, when the sample continued, depart toward the long key. This time-place curve was affected by sample base rate: The probability of pigeons going directly to the long side after sample onset increased when long samples were more frequent than short samples, indicating a decrease of temporal control. We found no evidence of changes in temporal sensitivity. The results are most consistent with models of timing that take into account biasing effects and competition for stimulus control.