GABAergic mechanisms gate tactile discrimination learning

In contrast to mechanisms mediating synaptic plasticity, the pharmacological basis of perceptual learning remains to be clarified. Here we report that a specific form of perceptual learning is influenced by GABAergic mechanisms. We induced perceptual learning by Hebbian co-activation of the skin of the tip of the right index fingers in human subjects. Under placebo conditions, tactile 2-point discrimination was improved on the co-activated, but not on the left, index finger. This augmentation was completely eliminated by lorazepam, a GABA(A) receptor agonist. No drug effects were found on the left index finger indicating that the drugs had no effect per se on performance. The results demonstrate that perceptual learning is subject to pharmacological gating by basic mechanisms known to mediate and modulate synaptic plasticity. (C) 2003 Lippincott Williams Wilkins.