Als we wél bij bewustzijn zijn, dan blijft de hersenactivatie (als respons op een prikkel) niet ter plaatse maar breidt ze zich uit naar andere hersenregio's. Dit is congruent met de information integration theory van het bewustzijn. Die laatste stelt dat we bij bewustzijn de opgedane informatie integreren tot een geheel. Of omgekeerd, als onze hersencellen het contact met diverse andere hersencellen verliezen, dan leidt dit tot een verlies van bewustzijn.
De onderzoekers stellen dat we dus kunnen nagaan in hoeverre een patiënt bij bewustzijn is, door te controleren of de hersenactivatie (als reactie op een prikkel) lokaal blijft of dat ze zich verspreid over de hersenen.
uit: University of Wisconsin-Madison (2010, January 27). Brain responses during anesthesia mimic those during natural deep sleep. ScienceDaily.The brains of people under anesthesia respond to stimuli as they do in the deepest part of sleep -- lending credence to a developing theory of consciousness and suggesting a new method to assess loss of consciousness in conditions such as coma...
Then they used transcranial magnetic stimulation (TMS), a noninvasive technique to stimulate the brain cortical neurons from the scalp, in combination with electroencephalography (EEG), which recorded the TMS-evoked brain responses. What they found is a pattern that looks much as it does when the brain is in deep, non-rapid eye movement (non-REM) sleep, another condition when consciousness fades....
The team believes that the response patterns observed in the awake brain, characterized by long-lasting activations moving over time to different cortical areas, reflect the connectivity of the cortical areas activated by TMS. This could be because when we are awake, the cortex is involved in many activities which require a constant communication between different cortical areas. But in the unconscious brain, this connectivity is temporarily lost, and therefore the TMS-evoked brain responses remain localized.
Ferrarelli says the results lend weight to the idea that a breakdown of cortical connectivity is a key aspect of loss of consciousness, and are consistent with the "integrated information theory of consciousness."...
That is, that the loss of functional connectivity between brain regions is a characteristic that sleep and anesthesia share, and that we think might be causal in the loss of consciousness in both cases."
Tononi says that a similar test of cortical connectivity could be used to provide a non-invasive way to test an unresponsive patient for consciousness during anesthesia or in medical conditions such as coma.
"One practical application would be a test to help assess how conscious a patient is...
Dido
