Abstract: DESCRIPTION (provided by applicant): Performance on visual tasks improves with training. Our long-term goal is to understand the neural changes that give rise to this form of perceptual learning. We use a task that requires a decision about the direction of weak motion signals in a random-dot stimulus. With training, monkeys, like humans, learn to interpret these motion signals more accurately and quickly. We will identify the neural substrate of these performance gains. In monkeys, several mechanisms contribute to decision formation. Neurons in the middle temporal area (MT) represent the motion information used to perform the task. When the decision is indicated with an eye movement, oculomotor circuits appear to accumulate this motion information over time to form the decision. Our three Specific Aims will identify changes in these mechanisms as performance improves with training. Aim 1 will identify changes in how the brain represents the sensory stimulus. We will record from MT neurons to test whether their sensitivity to motion changes as performance improves. Aim 2 will identify changes in how the brain interprets motion information to form the behavioral response. We will evoke saccadic eye movements with electrical microstimulation of the frontal eye field. These evoked saccades are sensitive to developing oculomotor commands and thus will be used to test how the accumulation process represented in these commands changes with training. Aim 3 will identify changes in how the brain computes the decision. We will record from neurons in the lateral intraparietal area that represent formation of the decision and formation of the eye-movement response in a trained monkey. We will determine how these different neural computations become linked over the course of training. In the long term, these studies will help connect systems-level electrophysiology with the study of plasticity and learning. These connections will aid in the development of computational tools to treat learning disabilities and clinical disorders (e.g., psychosis, dementia and agnosia) that affect the brain's ability to process and interpret information.

Public Health Relevance: This Public Health Relevance is not available.

Thesaurus Terms:
discrimination learning, neural information processing, neural plasticity, neuropsychology, sensory discrimination, temporal lobe /cortex, visual perception
electrophysiology, eye movement, motion perception, neural transmission, neuroanatomy, parietal lobe /cortex, sensory cortex, visual stimulus, visual threshold, visual tracking
Macaca mulatta, behavioral /social science research tag, electrode, electrostimulus, magnetic resonance imaging

Institution: UNIVERSITY OF PENNSYLVANIA
3451 Walnut Street
PHILADELPHIA, PA 19104
Fiscal Year: 2006
Department: NEUROSCIENCE
Project Start: 01-AUG-2004
Project End: 30-JUN-2009
ICD: NATIONAL EYE INSTITUTE
IRG: CVP

Neural correlates of perceptual learning in a sensory-motor, but not a sensory, cortical area

Chi-Tat Law¹ & Joshua I Gold¹

Abstract :
This study aimed to identify neural mechanisms that underlie perceptual learning in a visual-discrimination task. We trained two monkeys (Macaca mulatta) to determine the direction of visual motion while we recorded from their middle temporal area (MT), which in trained monkeys represents motion information that is used to solve the task, and lateral intraparietal area (LIP), which represents the transformation of motion information into a saccadic choice. During training, improved behavioral sensitivity to weak motion signals was accompanied by changes in motion-driven responses of neurons in LIP, but not in MT. The time course and magnitude of the changes in LIP correlated with the changes in behavioral sensitivity throughout training. Thus, for this task, perceptual learning does not appear to involve improvements in how sensory information is represented in the brain, but rather how the sensory representation is interpreted to form the decision that guides behavior.

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