Navegando por Autor "Macedo, Edson Anibal de"
Agora exibindo 1 - 2 de 2
- Resultados por página
- Opções de Ordenação
Artigo Cross-modal responses in the primary visual cortex encode complex objects and correlate with tactile discrimination(2011-09-13) Vasconcelos, Nivaldo; Pantoja, Janaina; Belchior, Hindiael; Caixeta, Fábio Viegas; Faber, Jean; Freire, Marco Aurelio M.; Cota, Vinícius Rosa; Macedo, Edson Anibal de; Laplagne, Diego Andrés; Gomes, Herman Martins; Ribeiro, Sidarta Tollendal GomesCortical areas that directly receive sensory inputs from the thalamus were long thought to be exclusively dedicated to a single modality, originating separate labeled lines. In the past decade, however, several independent lines of research have demonstrated cross-modal responses in primary sensory areas. To investigate whether these responses represent behaviorally relevant information, we carried out neuronal recordings in the primary somatosensory cortex (S1) and primary visual cortex (V1) of rats as they performed whiskerbased tasks in the dark. During the free exploration of novel objects, V1 and S1 responses carried comparable amounts of information about object identity. During execution of an aperture tactile discrimination task, tactile recruitment was slower and less robust in V1 than in S1. However, V1 tactile responses correlated significantly with performance across sessions. Altogether, the results support the notion that primary sensory areas have a preference for a given modality but can engage in meaningful cross-modal processing depending on task demand.Apresentado em Evento Representation of freely-explored objects in the primary somatosensory cortex and hippocampus(2010-09) Vasconcelos, Nivaldo; Macedo, Edson Anibal de; Corso, Gilberto; Gomes, Herman; Nicolelis, Miguel; Ribeiro, Sidarta Tollendal GomesWhen a rat freely explores an object in the dark and its whiskers touch different parts of the object with different velocities and angles, tactile information reaches the telencephalon with tantalizing spatio-temporal complexity. To investigate the tactile representation of freely-explored objects in the telencephalon, we performed multielectrode extracellular spike recordings from the primary somatosensory cortex (S1) and hippocampus (HP) of adult rats, as they freely explored novel objects in the dark. Neuronal data were fed to five different binary classifiers: multilayer perceptron, radial basis functions, support vector machines, decision tree and naive Bayes classifier. The classifiers were evaluated using the area under a receiver operating characteristic curve (AUROC). In most cases, it was possible to achieve substantial and significant object classification in both S1 and HP (>0.75 AUROC medians, corrected p<0.05). To assess the distribution of information across neuronal ensembles recorded from S1 and HP we performed a neuron dropping analysis, a bootstrap method that reveals how much information is lost, on average, as neuronal ensembles decrease their size from “n” to 1 neuron. We found that significant object classification is achieved with ensembles as small as 10 neurons in both S1 and HP. The best fit for the neuron dropping curves was akin to a type II functional response curve, which in ecology describes the decelerating intake rate of a consumer as a function of food density. We propose that the representation of freely-explored complex objects by neuronal ensembles in S1 and HP is robust, highly distributed, and shaped by the limited availability of non-redundant information to individual neurons.