Activation of M1 cholinergic receptors in mouse somatosensory cortex enhances information processing and improves detection behaviour

An important function of the brain is to form accurate representations of the world around us. To optimise sensory representations based on the demands of the environment, activity of cortical neurons is regulated by neuromodulators such as Acetylcholine (ACh). As such, ACh is implicated in cognitive functions including attention, arousal and sleep cycles. However, it is not clear how specific ACh receptors shape the baseline activity of cortical neurons and their evoked response to sensory stimuli. Here, we investigate the role of a densely expressed muscarinic ACh receptor 1 (M1) in information processing in the mouse primary somatosensory cortex (vS1) and in the animals sensitivity in detecting vibrotactile stimuli. We show that M1 activation significantly enhances the evoked response of vS1 neurons and the reversal of this enhancement by blocking M1. In addition, we demonstrate that M1 activation results in faster and more reliable neuronal responses, which is manifested by a significant reduction in response latencies and the trial-to-trial variability in neuronal activity. At the population level, M1 activation reduces the network synchrony and thus enhances the capacity of vS1 neurons in conveying sensory information. Consistent with the neuronal findings, we show that M1 activation significantly improves performances in a vibrotactile detection task. Overall, the M1-mediated enhancement in sensory efficiency reflects a multiplicative gain modulation at the neuronal level, resembling the changes observed during high attention states.