The long-term goal is to localize the neural structures involved in associative learning of auditory signals. Experiments with 2- deoxyglucose (2-DG) techniques have been designed to functionally map the neural metabolic activity related to the specific components involved in auditory conditioning, namely auditory conditioned stimulus (CS), unconditioned stimulus reinforcers (US), and conditioned responses (CR). Are the learned properties of a sound differentially represented at various levels of the auditory pathway? Which are the brain structures related to attentional and learning processes involved in associative learning? Two experimental protocols have been designed to address these questions using a combination of classical and operant conditioning paradigms in conjunction with autoradiographic 2-DG techniques for the study of behavior in freely moving animals. The basic idea is to quantitate the uptake of 2-DG in the brain of rats during a variety of different behavioral conditioning and control situations. The proposed experiments manipulate the specific components involved in auditory conditioning (CS, US, CR) in an effort to discriminate the neural representation, in terms of 2-DG uptake, of these components independently or combined in paired and unpaired trials. In the first protocol two CSs will be compared, using a differential paradigm with reinforced (CS+) and nonreinforced (CS-) presentations, in order to discriminate the tonotopic from the reinforcing effects of CSs in terms of 2-DG uptake. The 2- DG method provides a tool that allows simultaneous visualization of tonotopic representation and functional activity in the auditory system. This method will be used also in a second protocol comparing the effects of identical CS-US pairings on the brains of four groups of rats: performing animals trained to bar press for reward during a sound signal (discriminative group), or bar pressing regardless of sound (nondiscriminative group), and rats yoked to the above groups and subjected to paired CS-US (classical group) and unpaired CS-US (control group), respectively. It is expected that comparisons using complementary stimulus- response conditions will serve to elucidate the neuroanatomical structures related to the specific components involved in auditory conditioning. The most important outcome of the proposed research would be the identification and functional mapping of rat brain structures responsible for the associative learning and memory of auditory stimuli.
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