An investigation of Hebbian phase sequences as assembly graphs

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 (Naïve 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 assemblies correspond to primitive building blocks of representation, nearly unchanged in 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.

Repercussões da terapia comunitária no processo de trabalho na estratégia saúde da família: um estudo representacional

The Community Therapy (CT) is in a practice of therapeutic effect and may also be considered as a technology takes care of the therapeutic procedure group, whose purpose is to promote health, prevent illness, developed within primary care in mental health. In this study we sought to understand the social representations of health professionals who work with the Community Therapy, on use of the Family Health Strategy (FHS) in the city of Joao Pessoa. This is a field research with a qualitative view Moscovician Theory of Social Representations, held with seven professionals of the FHS, therapists of Community Health District II. The empirical data were obtained by carrying out two thematic therapies in April 2009, which were wheeled CT. It was used as a technique for analyzing the collective subject discourse, and the data presented through graphs, charts, maps, pictures and graphics and arranged in three stages: Subjects of the study, characterizing the study participants; Social Representations of Therapist Community presenting and discussing the social representations of therapists community studied on CT, and Consequences of Community Therapy at the Family Health Strategy, discussing the meanings attributed by the study participants about changes in FHS. Meanings were attributed to the CT by the therapists studied originated from the speeches, songs, drawings and constructed, and that presented by schematic illustration show the relation between the representations: life, listening, faith / light, change, transformation. The web, symbol of CT, appeared on the images constructed by the representatives of the study and represents the formation of bonds that allows the construction of social support networks that strengthen relationships among community. In the study, proved by professionals who have the meanings about the changes in the work process from the introduction of CT, and shown that the change took place within a more welcoming attitude on the part of professionals, the relationship between Team members had no significant changes, explained by the low compliance of team members to the CT in relation to the user front, the bond was strengthened, and this involved strengthening the role of the therapist community. It is recognized, thereby transforming the character of CT in building links with users, requiring, however, that the team is viewed as offering therapeutic services, not the professional therapist. Therefore, the CT for being a new phenomenon in health services and community belonging, it fits like a novelty which affects the construction of a representation dispute. Still, can contribute to the reorganization of mental health care in line with the new model of mental health care advocated by the Psychiatric Reform.

An investigation of Hebbian phase sequences as assembly graphs

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 (Naïve 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 assemblies correspond to primitive building blocks of representation, nearly unchanged in 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.