Two directions of plasticity in the sensory-deprived adult cortex.

Damage or deprivation of a localized region of the skin surface has been shown to induce a selective expansion of adjacent skin surface representations in the adult somatosensory cortex. Here, we use repeated optical imaging in conjunction with single unit recordings to assess the plasticity of a single whisker's functional representation in the adult rat. We observed a large-scale expansion of a single whisker's functional representation following innocuous removal of all neighboring whiskers. Surprisingly, the same manipulation can also induce a large-scale contraction of the representation if the animal is removed from its home cage and given a brief opportunity to use its whiskers for active exploration of a different environment. Both the expansion and contraction reverse upon regrowth of the deprived whiskers. Thus, allowing the animal to use its deprived receptor organ in active exploration can determine the direction of plasticity in the adult cortex.