Brains disconnect as people sleep.Consciousness fades during sleep not because the brain shuts down but because it loses its capacity to integrate information via networks of interconnected areas, a new study suggests.
Giulio Tononi of the University of Wisconsin-Madison “University of Wisconsin” redirects here. For other uses, see University of Wisconsin (disambiguation).
A public, land-grant institution, UW-Madison offers a wide spectrum of liberal arts studies, professional programs, and student activities. and his colleagues studied six adults who sat in reclining chairs with their eyes closed and gradually fell asleep. The researchers used a technique called transcranial magnetic stimulation Transcranial magnetic stimulation
A procedure used to treat patients with depression.
Mentioned in: Magnetic Field Therapy
transcranial magnetic stimulation,
n to generate mild magnetic pulses that briefly activated the right-premotor area of each participant's brain. The team targeted that area because it connects to many other parts of the brain.
In volunteers who were awake, magnetic prodding of the premotor area elicited a rise in electrical activity within a fraction of a second, as measured by sensors in a cap worn by each volunteer. Over the next several seconds, brief waves of electrical activity appeared in four other brain regions, the scientists report in the Sept. 30 Science.
During bouts of deep sleep early in the night, the magnetic stimulation magnetic stimulation Neurology A noninvasive method for stimulating the brain and nerves, with a high-current magnetic pulse passed through a coil of wire induced a stronger initial surge of premotor-electrical activity than had occurred during wakefulness wakefulness
believed to occur when the tonic flow of impulses from the reticular activating system exceeds the critical level for sustaining consciousness; reduction of reticular activating system activity is the basis of the pharmacological induction of sedation. . However, that activity rapidly vanished, and brain regions with premotor connections showed no subsequent signs of arousal arousal /arous·al/ (ah-rou´z'l)
1. a state of responsiveness to sensory stimulation or excitability.
2. the act or state of waking from or as if from sleep.
When the researchers magnetically stimulated tissue in another brain network, neural activity again spread only while participants were awake.
Tononi's group plans to investigate whether communication across brain regions partly recovers during late-night sleep and especially during periods of rapid eye movement rapid eye movement
Abbr. REM The rapid periodic jerky movement of the eyes during certain stages of the sleep cycle when dreaming takes place. , when dreaming is common.--B.B.