Figure 1.

Visual perceptual learning induces long-term potentiation in the primary visual cortex. A modified version of the visual water box task is used to induce visual perceptual learning (PL) in a group of adult rats (panel A) that are first trained to distinguish a low 0.117 cycles per degree (c/deg) spatial frequency (SF) grating (reference grating) from a 0.712 c/deg SF grating (test grating) and then learned to distinguish the two gratings when they became more and more similar to each other. Two groups of control animals are trained to either distinguish the reference grating from a homogeneous gray (panel B) or to distinguish a low SF vs. a never changing high SF panel (panel C, thus lacking the incremental training). After training, LTP from layer II-III of V1 slices is occluded in PL animals compared to controls, at the level of both vertical and horizontal connections.