Project Summary Auditory experience can reshape cortical maps and transform receptive field properties of neurons in the auditory cortex of the adult animal. The exact form of this plasticity depends on the behavioral context, and the spectrotemporal features of the salient acoustic stimuli. This has been shown by combined physiological and behavioral approaches in our previous experiments in which spectrotemporal receptive fields (STRFs) were rapidly and comprehensively characterized simultaneous with the animal behavior. The experiments also contrasted plasticity in single cells across different auditory tasks employing various acoustic signals with controlled spectral and temporal features. These results are consistent with findings of adaptive plasticity in the motor and other sensory systems and support the hypothesis that auditory cortical cells may undergo rapid, context-dependent changes of their receptive field properties when an animal is engaged in different auditory behavioral tasks. This kind of plasticity would likely involve a selective functional reshaping of the underlying cortical circuitry to sculpt the most effective receptive field for accomplishing the current auditory task. During the last 5 years, we explored how this plasticity manifested itself in the dPEG and VPr fields of the ferret auditory cortex. In this grant period, we hope to complete the characterization of this plasticity and also examine its role in two important cognitive functions: Categorization and Encoding of Sequences. We shall conduct our physiological experiments with dense arrays of planar and laminar multielectrode arrays, as well as functional Ultrasound imaging to gain a view of the global distribution of neuronal activity during and after training These experiments will lead to progress in understanding the interactions within an extended neuronal network covering most of the auditory posterior cortical fields in the ferret which give rise to adaptive plasticity.