Anesthesia-induced loss of consciousness disrupts auditory responses beyond primary cortex

Amit Aaron PNAS

One of the most obvious affects of anaesthesia is that our patients are disconnected from their sensory environment: they don’t respond to questions, they don’t see the operation and they don’t feel the pain of surgery. However it is far from obvious where in the sensory hierarchy this disconnection occures. In this project we used intracranial depth-electrode recordings from single neurons in neurosurgical patients to map auditory responses as they went from wakefulness to anaesthesia. We showed that signals continued to arrive relatively unchanged to primary auditory cortex, but even only a little higher in the hierarchy, only millimeters away, the signals were disrupted. Furthermore we found evidence that feed-back signals in the brain were more affected by loss of consciousness, and a perhaps surprising difference between changes in high gamma responses (increased with anaesthesia) and neuronal firing (decreased with anaesthesia).