Researchers have captured what happens in the split second before the emergence of consciousness, a fundamental state of human life.
“Without consciousness, nothing else matters…”
At the precise moment we become aware of stimuli, a wave of electrical activity flows from the visual cortex in the rear of the brain to the frontal lobes, the researchers report.
“There is a very tight window of a few milliseconds when we [become] aware of stimuli and before the experience is passed on to be coded in our memory and analyzed,” says Hal Blumenfeld, professor of neurology at Yale University and senior author of the research, which appears in the journal Cerebral Cortex.
Information about events around us constantly bombard our brains, but we only become conscious of a few of them. When stimuli do not trigger consciousness, the visual cortex activates but there is no wave and information is not passed on.
In the milliseconds when subjects become conscious of a stimulus and the wave begins, the visual cortex switches off—as does brain’s default mode, when the brain is idling and processing internal thoughts.
“It is a switch and wave network that allows the brain to concentrate on the stimuli undistracted,” Blumenfeld says.
The research team surgically embedded sensors in the brains of subjects and then, while the participants watched a movie, showed them flickering images of a face. The researchers recorded local changes in the visual cortex regardless of whether subjects reported seeing the faces. But widespread switch and wave-like electrical activity in the brain was striking and consistent only as subjects became consciously aware of the faces on the screen, the researchers report.
Limits on consciousness play a role in a host of maladies, from coma and Alzheimer’s to attention deficit disorder and schizophrenia. Consciousness is central to all human existence, whether sick or healthy, Blumenfeld argues.
“Without consciousness, nothing else matters,” he says. “Our quality of life itself is tied to consciousness.”