Expanded domain of learning-induced primary auditory cortical plasticity

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DESCRIPTION (provided by applicant): Auditory learning is accompanied by specific physiological plasticity in the primary auditory cortex (A1). The processing and representation of acoustic frequencies and other acoustic parameters that gain behavioral importance through learning are generally emphasized, e.g., by selective decreased threshold or tuning shifts to the frequency of a reinforced stimulus. Research in learning-induced auditory plasticity has mainly focused on determinations of which acoustic parameters are affected (e.g., frequency, level, FM modulation). Recent studies indicate that there is a need to take into account non-auditory factors. The goals of this research project are to determine some of the factors that influence the induction of associative learning-induced cortical plasticity and to investigate the functional behavioral effects of the development of such specific plasticity. The proposed experiments were designed after initial research showed that the development of specific plasticity in A1 was determined not by the magnitude of learning or the amount of learning about absolute frequency, but rather by the type of learning strategy used to solve the apparently simple problem of bar-pressing for water, contingent on the presence of a tone. I will investigate factors that are likely to play important roles in governing frequency-specific plasticity in the primary auditory cortex in auditory associative memory: learning strategy and amount of training. I will also explore possible behavioral functional effects of learning-induced cortical plasticity: improved perceptual detectability and stronger memory. Instrumental conditioning of rats to bar-press for water rewards contingent upon tone presentations will be used to study learning, specificity of behavior and the strength and specificity of associative memory. Complete electrophysiological recordings across the entire rat hearing frequency range in primary auditory cortex will be used to correlate tuning changes with behavior. The findings will help to illuminate some of the learning influences on specific auditory cortical plasticity (learning strategy, length of training) and establish its relationship to behavior both perceptually (conditioned stimulus detectability) and mnemonically (strength of associative memory). Findings from the proposed studies could be used towards the development of auditory learning therapies for use after artificial cochlear implantation in humans to help acquire higher-level auditory function. The results from the proposed experiments could also lead to the development of ideal non-invasive therapies using learning tasks that induce cortical plasticity for regain of function after stroke, or other cortical destruction.