Why do we lose consciousness?

THAT'S THE WHY:If you've ever had surgery under general anaesthetic, hopefully you don't remember it. But why do our brains turn down the dimmer switch as the drugs hit? What happens when we lose that conscious awareness?

A study presented at a major conference last month may offer a glimpse into the inhibitory changes that sweep through the brain as we go under.

The research, presented at Euroanaesthesia 2011, used a technology with the tongue-twisting name “functional electrical impedance tomography by evoked response”.

Developed at the University of Manchester, the device uses 32 electrodes around the patient’s head and monitors electrical activity deep within the brain.

By looking at healthy volunteers and anaesthetised patients scheduled for surgery,

the researchers have been studying three-dimensional images of conductivity changes in the brain, watching what happens to communications between groups of brain cells.

“Our findings suggest that unconsciousness may be the increase of inhibitory assemblies across the brain’s cortex,” says Prof Brian Pollard from the University of Manchester in a release.

“We have been able to see a real-time loss of consciousness in anatomically distinct regions of the brain for the first time.

“We are currently working on trying to interpret the changes that we have observed. We still do not know exactly what happens within the brain as unconsciousness occurs, but this is another step in the direction of understanding the brain and its functions.”