Perceptual Learning Directs Auditory Cortical Map Reorganization through Top-Down Influences

• Published in: The Journal of neuroscience 2006-05, Vol.26 (18), p.4970-4982
• Main Authors: Polley, Daniel B, Steinberg, Elizabeth E, Merzenich, Michael M
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Animals; Auditory Cortex - cytology; Auditory Cortex - physiology; Auditory Perception - physiology; Auditory Threshold - physiology; Behavior, Animal; Brain Mapping; Dose-Response Relationship, Radiation; Evoked Potentials, Auditory - physiology; Evoked Potentials, Auditory - radiation effects; Female; Models, Neurological; Neuronal Plasticity - physiology; Neuropsychological Tests; Rats; Reaction Time - physiology; Recognition (Psychology) - physiology
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/JNEUROSCI.3771-05.2006

The primary sensory cortex is positioned at a confluence of bottom-up dedicated sensory inputs and top-down inputs related to higher-order sensory features, attentional state, and behavioral reinforcement. We tested whether topographic map plasticity in the adult primary auditory cortex and a secondary auditory area, the suprarhinal auditory field, was controlled by the statistics of bottom-up sensory inputs or by top-down task-dependent influences. Rats were trained to attend to independent parameters, either frequency or intensity, within an identical set of auditory stimuli, allowing us to vary task demands while holding the bottom-up sensory inputs constant. We observed a clear double-dissociation in map plasticity in both cortical fields. Rats trained to attend to frequency cues exhibited an expanded representation of the target frequency range within the tonotopic map but no change in sound intensity encoding compared with controls. Rats trained to attend to intensity cues expressed an increased proportion of nonmonotonic intensity response profiles preferentially tuned to the target intensity range but no change in tonotopic map organization relative to controls. The degree of topographic map plasticity within the task-relevant stimulus dimension was correlated with the degree of perceptual learning for rats in both tasks. These data suggest that enduring receptive field plasticity in the adult auditory cortex may be shaped by task-specific top-down inputs that interact with bottom-up sensory inputs and reinforcement-based neuromodulator release. Top-down inputs might confer the selectivity necessary to modify a single feature representation without affecting other spatially organized feature representations embedded within the same neural circuitry.