Monday, March 31, 2008

Aversive learning enhances perceptual and cortical discrimination

Li, W, Howard, J.D., Parrish, T.B., & Gottfried, J.A. (March 28, 2008). Aversive learning enhances perceptual and cortical discrimination of indiscriminable odor cues. Science, Vol. 319, 1842-1844.

With this study, the authors explored the impact of aversive conditioning on olfactory discrimination. While most conditioning studies examine the acquisition of new behavioral responses (CR) to formerly benign stimuli presentations, this examined how associative learning can actually alter the perceptual processing of the conditioned stimulus (CS) itself. Following a conditioning regimen, behavioral accuracy for distinguishing by smell between a previously indistinguishable pair of molecules (CS+) rose by more than a factor of 2, exceeding both chance and preconditioning performance. Interestingly, following conditioning, no improvement in distinguishing between the unconditioned control pair (CS-) was witnessed, indicating that these effects are specific to the CS+. After conditioning, reorganization of neural coding was also observed in the posterior piriform cortex, where neural representations of odor identity are maintained. This may shed new light on anxiety disorders which are characterized by exaggerated sensory sensitivity and hypervigilance, potentially self-reinforcing patterns.

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