Cholinergic modulation of stimulus-specific adaptation and prediction error responses in the auditory cortex of the rat

Résumé

A fundamental property of sensory systems is their ability to detect novel stimuli in the environment. The auditory brain contains neurons that decrease their response to repetitive sounds but increase their firing rate against novel or deviant stimuli; the difference between both responses is known as stimulus-specific adaptation (SSA) or neuronal mismatch. This thesis describes 1) the properties of excitatory (fast spiking) and inhibitory (regular spiking) auditory cortical neurons, 2) how acetylcholine (ACh) modulates SSA in the rat auditory cortex and 3) how rats can discriminate behaviorally relevant novel sounds. Results show that 1) fast spiking and regular spiking neurons show similar amounts of deviance detection, 2) ACh increases SSA by ~31% in the auditory cortex. Importantly, ACh increased the neuronal firing rate in response to deviant tones only, and only the prediction error component was affected. This thesis also demonstrates that ACh increases the precision of prediction error signaling and is mediated by muscarinic receptors, gating prediction errors to hierarchically higher processing levels. Finally, 3) the training on the auditory discrimination task had effects on neuronal activity, increasing the deviant detection, neuronal mismatch and prediction error responses.