Auditory Predictive Coding across Awareness States under Anesthesia: An Intracranial Electrophysiology Study
Journal of Neuroscience August 20, 2018 K. Nourski, M. Steinschneider, A. Rhone et al.
During propofol anesthesia, loss of consciousness (LOC) is accompanied by a loss of auditory novelty responses (local deviance effects) in higher-order cortical areas beyond auditory cortex, while responses to longer-timescale novelty (global deviance effects) are suppressed under sedation and absent after LOC. However, the absence of global deviance effects does not reliably indicate LOC. The study recorded electrocorticographic signals from four hierarchical cortical levels in six neurosurgical patients. Local deviance effects were preserved in all regions except prefrontal cortex during sedation, and after LOC they were lost outside auditory cortex. Global deviance effects were suppressed under sedation and absent after LOC. The loss of local deviance effects in higher-order areas may serve as an alternative biomarker of LOC.