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Hearing and Donuts (Brain and Bagels) Seminar
December 13, 2019 @ 8:30 am - 9:30 am
Presenter: Kirill Nourski, MD, Ph.D., Research Faculty (Neurosurgery), Univ. of Iowa
Topic: Cortical Responses to Auditory Novelty Across Awareness States and Task Conditions: Intracranial Electrophysiology Studies
Development of a biomarker that can reliably index changes in the brain upon loss of consciousness (LOC) has broad implications for elucidating the neural basis of awareness. Clinically relevant conditions include sedation, LOC under general anesthesia, natural sleep, and disorders of consciousness. Using intracranial recordings from neurosurgery patients, we investigated responses to auditory novelty over short (‘local deviance’) and long (‘global deviance’) time scales. We described distinct patterns of activation of cortical networks involved in auditory novelty detection. Local deviance was associated with predominantly feedforward signaling along the auditory cortical hierarchy, while global deviance detection featured a more complex bidirectional information flow. Changes in cortical novelty responses associated with sedation and LOC under propofol anesthesia indicate that while the presence of global deviance effects can index awareness, their loss cannot serve as a biomarker for LOC. Indeed, global deviance effects were strongly driven by task demands, unlike the more robust local deviance effects and overall activation by auditory stimuli. By contrast, the dramatic reduction of local deviance effects in areas beyond canonical auditory cortex may constitute an alternative biomarker of LOC.