Plasticity in Adult Auditory Cortex:
From Neuromodulation to Perception

Résumé :

The disciplines of sensory physiology and the neurobiology of learning/memory both focus on the processing of sensory information but have developed separately since the 19th Century. However, their basic experimental paradigms are actually complementary. Hybrid experimental designs that incorporate both paradigms have revealed that learning/memory involve systematic changes in the primary auditory cortex of adult animals and also humans, e.g., a shift of tonal receptive field frequency tuning toward or to the frequency of a behaviorally important sound. Such plasticity has all of the characteristics of associative memory, including specificity, consolidation and long term retention. The nucleus basalis cholinergic system is sufficient to induce both receptive field plasticity and also behavioral memory. Receptive field plasticity increases the area of cortex that becomes tuned to a significant sound, suggesting that there exists a neural Memory Code for acquired stimulus importance, i.e., the area (number of cells) of stimulus representation. This hypothesis is supported by recent studies that demonstrate a direct relationship between tone control of behavior and the size of best cortical tuning to that stimulus. Overall, the findings indicate that the functional organization of primary sensory cortex reflects the storage of learned information throughout life span, i.e., is a direct substrate of memory.