A Theory of Perceptual Categorization in Primates Program No. 538.7. 2005 Abstract Viewer/Itinerary Planner

S.E. LEW, H.G. REY, S.B. ZANUTTO

Washington, DC

Congreso; Annual Meeting of the Society for Neuroscience.; 2005

Society for Neuroscience

Abstract View A THEORY OF PERCEPTUAL CATEGORIZATION IN PRIMATES S.E.Lew1,2*; H.G.Rey1,2; S.B.Zanutto1,2 1. IIBM, FIUBA, Buenos Aires, Argentina 2. IBYME, CONICET, Buenos Aires, Argentina A neural network model explaining perceptual categorization is proposed. The role of the prefrontal and premotor cortices (PFC and PMC), their interaction with cathecolaminergic structures and, plasticity and activity modulation mechanisms are formalized. In this model, dopamine neurons in the ventrotegmental area (VTA) learn to predict upcoming rewards. Depending on this prediction, PFC and PMC neurons modify their synaptic weights using a hebbian or antihebbian rule. After training, some PFC neurons code learned rules while the remaining ones learn no associations with task relevant responses. However, removing these PFC clusters decreases the overall performance due to system instability. We also propose cathecolaminergic modulation to reproduce exploratory behaviors observed at the beginning of the training and reversal. Information from sensory, inferotemporal and parietal cortices, hippocampus and amygdala converge at the ventromedial PFC, where reward related stimuli are enhanced. We propose that these stimuli generate short term memory, allowing the system to learn simple operant tasks when the dorsolateral PFC (DLPFC) is impaired. Nevertheless, working memory of task relevant stimuli is generated in the DLPFC. The cathecolaminergic modulation improves PFC signal to noise ratio performing a winner take all rule. DLPFC clusters learn to code sample-comparison compound stimuli. Connections between the DLPFC and motor structures (including PMC) clusters, learn the associations between each compound stimuli and a task related response. To test some predictions of the model, we performed a delay matching to category (DMC) experiment with humans. Once the subjects learn to categorize inside a restricted space of morphed stimuli, they can generalize over not trained regions. At the categories border, the latency to respond raises and the performance decreases. In addition, the model predicts other relevant results related to delay matching to sample and DMC paradigms as response selection, stimulus selectivity, latency to half selectivity and category preference in PFC. Citation:S.E. Lew, H.G. Rey, S.B. Zanutto. A THEORY OF PERCEPTUAL CATEGORIZATION IN PRIMATES Program No. 538.7. 2005 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2005. Online.   2005 Copyright by the Society for Neuroscience all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing from the SfN office prior to publication