Stimulus-specific adaptation in the inferior colliculus: The role of excitatory, inhibitory and modulatory inputs.

Patients suffering from pathologies such as schizophrenia, depression or dementia exhibit cognitive impairments, some of which can be reflected in event-related potential (ERP) measurements as the mismatch negativity (MMN). The MMN is one of the most commonly used ERPs and provides an electrophysiological index of auditory change or deviance detection. Moreover, MMN has been positioned as a potentially promising biomarker candidate for the diagnosis and prediction of the outcome of schizophrenia. Dysfunction of neural receptors has been linked to the etiopathology of schizophrenia or the induction of psychophysiological anomalies similar to those observed in schizophrenia. Stimulus-specific adaptation (SSA) is a neural mechanism that contributes to the upstream processing of auditory change detection. Auditory neurons that exhibit SSA specifically adapt their response to repetitive sounds but maintain their excitability to respond to rare ones. Thus, by studying the role of neuronal receptors on SSA, we can contribute to detangle the cellular bases of the impairments in deviance processing occurring in mental pathologies. Here, we review the current knowledge on the effect of GABAA-mediated inhibition and the modulation of acetylcholine on SSA in the inferior colliculus, and we add unpublished original data obtained blocking glutamate receptors. We found that the blockade of GABAA and glutamate receptors mediates an overall increase or decrease of the neural response, respectively, while acetylcholine affects only the response to the repetitive sounds. These results demonstrate that GABAergic, glutamatergic and cholinergic receptors play different and complementary roles on shaping SSA.