Cholinergic depletion prevents expansion of topographic maps in somatosensory cortex

Although the role of acetylcholine in processing stimuli in the cerebral cortex is becoming defined, the impact of cholinergic activity on the character of cortical maps remains unclear. In the somatosensory cortex, topographic maps appear capable of lifelong modifications in response to alterations in the periphery. One factor proposed to influence this adaptational ability is the presence of acetylcholine in the cortex. The studies presented here, using the 2-deoxyglucose technique, demonstrate that the unilateral removal of a digit in cats, followed by stimulation of an adjacent digit, produces a pattern of metabolic activity in the somatosensory cortex that is dramatically expanded when compared with the opposite (normal) hemisphere. In contrast, experiments in which the somatosensory cortex was depleted of acetylcholine and the animal received a similar amputation led not to patterns of expanded metabolic activity, but rather to reductions in the evoked metabolic distribution. These studies implicate acetylcholine in normal map formation and in the maintenance of the capacity of cortical maps to adapt to changes in the periphery.