Significance How the brain deals with the barrage of sensory information during wakefulness determines cognitive performance. Strategies include bias toward attending to novel sensory information and an ability to enhance or habituate cortical responses to repeated inputs. Here we show both enhancement and habituation occur simultaneously in different layers of cortex and that the plastic processes involved require activation of the GABA _B subtype of neuronal inhibition. The work demonstrates that the brain can change the way it routes repeatedly presented sensory information in two complementary ways: It optimizes the local cortical representation, including more information as the stimulus is repeated; and it minimizes the output to other areas, preserving only outputs most closely correlated with the local cortical representation.