Automatic Sensory Predictions: A Review of Predictive Mechanisms in the Brain and Their Link to Conscious Processing

The brain automatically integrates sensory information to form predictions about future events, a process studied through predictive coding. While initially developed for vision, most research has focused on auditory processing, using the mismatch negativity signal as a key measure of prediction error. Auditory prediction errors occur across various states of consciousness, and their presence and characteristics are linked to residual levels of consciousness and the return of awareness. This review covers the neural substrates of auditory predictive processes and their relation to consciousness, then examines how these processes are modulated in states like wakefulness, sleep, anesthesia, coma, meditation, and hypnosis. Future research combining electrophysiological and computational techniques may clarify which predictive processes remain when consciousness fades.

Study at a glance

Abstract

The human brain has the astonishing capacity of integrating streams of sensory information from the environment and forming predictions about future events in an automatic way. Despite being initially developed for visual processing, the bulk of predictive coding research has subsequently focused on auditory processing, with the famous mismatch negativity signal as possibly the most studied signature of a surprise or prediction error (PE) signal. Auditory PEs are present during various consciousness states. Intriguingly, their presence and characteristics have been linked with residual levels of consciousness and return of awareness. In this review we first give an overview of the neural substrates of predictive processes in the auditory modality and their relation to consciousness. Then, we focus on different states of consciousness - wakefulness, sleep, anesthesia, coma, meditation, and hypnosis - and on what mysteries predictive processing has been able to disclose about brain functioning in such states. We review studies investigating how the neural signatures of auditory predictions are modulated by states of reduced or lacking consciousness. As a future outlook, we propose the combination of electrophysiological and computational techniques that will allow investigation of which facets of sensory predictive processes are maintained when consciousness fades away.