Behavioral & Systems Neuroscience Talk
Department of Psychology
Friday, October 26 - 3:00pm - Psychology Rm. 101
Institute for Systems Research, University of Maryland College Park
How attention shapes perception through cortical plasticity – insights from task-related plasticity in auditory and frontal cortices in the ferret.
Rapid task-related receptive field plasticity alters the tuning properties of neurons in primary auditory cortex (A1) in a task-specific fashion that enhances their ability to encode the salient spectral and temporal parameters of the current task. We find that the type and sign of plasticity is influenced by motivation, task design, demands, reward valence and overall task performance. We compared task-related plasticity for two categories of stimuli (reference and target stimuli) in A1 vs plasticity observed in secondary, tonotopic cortical areas in the posterior ectosylvian gyrus of the ferret. We also compared these responses in primary and secondary auditory cortex to the behaviorally gated task-related responses we have described in frontal cortex. We trained ferrets on a simple, conditioned avoidance auditory task in which the animals learned to discriminate tonal from noisy stimuli. In secondary areas, we found a relatively heightened response to targets vs. background stimuli during behavior, compared to responses observed in passive listening. This heightened response to the attended auditory target stimulus during behavior is a pivotal change that may lead to categorical encoding of the type we have described in frontal cortex. The secondary auditory cortex is thus likely to play a key role in the transformations of sound from spectrotemporal pattern to recognized auditory object to behavioral meaning from A1 to PFC.
The PFC is also known to play an influential role in controlling the flow of sensory inputs via top-down feedback to sensory cortical areas during behavior, reflecting attentional focus and task objectives and rules. Our recordings from PFC have shown striking behavioral gating of acoustic inputs; rapid, flexible and highly selective encoding of functional classes of acoustic stimuli; post-behavioral persistence of attention-driven modulation; and feature-selective changes in inter-areal coherence between A1 and PFC. These findings mirror earlier results in A1, showing that attention triggered rapid, selective, persistent, task-related changes in spectrotemporal receptive fields. Moreover, stimulation of PFC, paired with pure tone presentation, elicits changes in receptive fields that are similar to those observed in attention-driven behavior. These results suggest that PFC and auditory cortex dynamically establish a two-way functional connection during auditory behavior that controls the flow of salient sensory information and maintains a persistent trace of recent task-relevant auditory stimulus features. We speculate that that plasticity in the auditory network is driven not only by direct top-down projections from PFC to auditory cortex, but also by PFC pathways that recruit neuromodulators that are the engines of adaptive change in auditory processing.
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