thescientist | General anesthesia has transformed surgery from a ghastly ordeal to a
procedure in which the patient feels no pain. Despite its widespread
use, however, little is known about how anesthesia produces loss of
consciousness—a blind spot brought into sharp focus by the fact that
patients still occasionally wake up during surgery. But over the past 5
years, researchers have made significant progress in understanding what
happens in the brain as consciousness departs and returns.
Peering into the anesthetized brain with neuroimaging and
electroencephalograph (EEG) recordings, scientists have found evidence
to support the “integrated-information theory,” which holds that
consciousness relies on communication between different brain areas, and
fades as that communication breaks down. EEG studies have also revealed
distinctive brain wave patterns that signal when consciousness is lost
and regained, offering easily identifiable markers for this impairment
of communication.
Though many questions remain, advances in brain activity monitoring
promise to shed light the neural basis of consciousness, and to
eradicate the nightmare of mid-surgery awakenings. What’s more, by
combining EEGs with magnetic brain stimulation, researchers may be able
to measure consciousness and track recovery in unresponsive patients
diagnosed as “vegetative,” who in recent years have been shown to
sometimes have higher levels of consciousness than previously realized.
