title: Cholinergic modulation of response gain in the primary visual cortex of the macaque.
abstract: ACh modulates neuronal activity throughout the cerebral cortex, including the primary visual cortex (V1). However, a number of issues regarding this modulation remain unknown, such as the effect and its function and the receptor subtypes involved. To address these issues, we combined extracellular single-unit recordings and microiontophoretic administration of ACh and measured V1 neuronal responses to drifting sinusoidal grating stimuli in anesthetized macaque monkeys. ACh was found to have mostly facilitatory effects on the visual responses, although some cases of suppressive effects were also seen. To assess the functional role of ACh, we further examined how ACh modulates the stimulus contrast-response function, finding that the response gain increased with the facilitatory effect. The response facilitation was completely or strongly blocked by atropine (At), a muscarinic ACh receptor (mAChR) antagonist, in almost all neurons (96% of cells), whereas any residual effect after At administration was fully removed by mecamylamine, a nicotinic AChR (nAChR) antagonist, suggesting a predominant role for mAChRs in this mechanism. Furthermore, we found no laminar distribution bias for the facilitatory modulation, although the relative contribution of mAChRs was smaller in layer 4C than in other layers. The suppressive effect was blocked completely by At. These results demonstrate that ACh plays an important role in visual information processing in V1 by controlling the response gain via mAChRs across all cortical layers and via nAChRs, mainly in layer 4C.
authors: Graduate Schools of Frontier Biosciences and Medicine, Osaka Univ., 1-17 Machikaneyama, Toyonaka, Osaka, Japan.
authors: Shogo
authors: S
authors: Soma
authors: Satoshi
authors: S
authors: Shimegi
authors: Hironobu
authors: H
authors: Osaki
authors: Hiromichi
authors: H
authors: Sato
mesh_terms: D000109:Acetylcholine / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D059329:Cholinergic Neurons / Q000187:drug effects / Q000502:physiology*; D008251:Macaca; D010775:Photic Stimulation; D011976:Receptors, Muscarinic / Q000378:metabolism*; D014793:Visual Cortex / Q000187:drug effects / Q000502:physiology*; D014796:Visual Perception / Q000187:drug effects / Q000502:physiology*
chemical_list: D011976:Receptors, Muscarinic; D000109:Acetylcholine