The Shifting Structure of Brain Networks at the Transition into Unconsciousness
Laura Lewis, Harvard University
The discovery of anesthetic drugs revolutionized medicine, transforming surgery from a traumatic ordeal to a painless, precise procedure. However, how and why these drugs cause unconsciousness was still a mystery, leading to thousands of cases of accidental awakening every year. More broadly, the neuroscience of conscious states is at a very early stage, with many unanswered questions: how does the brain cause us to wake up, lose consciousness, dream, or hallucinate? This talk will outline some challenges and progress in the neuroscience of altered states of consciousness, and describe recent work focusing on how the brain switches between awake and unconscious states. We studied how anesthetics cause unconsciousness by recording brain activity in patients undergoing surgery, and by using genetically engineered viruses in mice to manipulate specific brain areas. These experiments have discovered patterns of brain activity that cause unconsciousness by fragmenting the brain’s network structure. They reflect a recent shift from a ‘global’ view of unconscious states to a ‘local’ one: that is, rather than an entire organism being awake or asleep, single regions of the brain may show sleep-like activity while other areas do not. We are now exploring how the principles discovered using anesthesia – how brain networks reorganize and thereby alter information processing – may enable the brain to generate other altered states of consciousness, such as dreams, hallucinations, and coma.