Cholinergic top-down modulation based on the free-energy principle

Acetylcholine (ACh) has a key role in the cortex in perception. Although cholinergic modulations have been revealed in recent experimental studies, it remains unclear what is the essential role of ACh. In order to clarify the crucial computational function of ACh in perceptual inference, we propose a model of cholinergic top-down modulation based on the free-energy principle in this paper. We made the only assumption that ACh modulates the magnitude of top-down processing. Then, dynamics of the ACh level is derived by the free-energy principle. Our model suggests that ACh reports uncertainty of top-down information and reduces noise of top-down input. Thus, ACh can contribute to precise perception.