18:00 19 April 2006
NewScientist.com news service
Everybody has experienced a sense of “losing oneself” in an activity — being totally absorbed in a task, a movie or sex. Now researchers have caught the brain in the act.
Self-awareness, regarded as a key element of being human, is switched off when the brain needs to concentrate hard on a tricky task, found the neurobiologists from the Weizmann Institute of Science in Rehovot, Israel.
The team conducted a series of experiments to pinpoint the brain activity associated with introspection and that linked to sensory function. They found that the brain assumes a robotic functionality when it has to concentrate all its efforts on a difficult, timed task — only becoming "human" again when it has the luxury of time.
Ilan Goldberg and colleagues used functional magnetic resonance imaging (fMRI) to scan the brains of nine volunteers during the study. Participants were shown picture cards and told to push buttons to indicate whether or not an animal was depicted.
The series was shown slowly the first time, and at three times the rate on the second run through. On its third showing, the volunteers were asked to use the buttons to indicate their emotional response to the pictures. The experiment was then repeated using musical extracts, rather than pictures, and asked to identify whether a trumpet played.
Goldberg found that when the sensory stimulus was shown slowly, and when a personal emotional response was required, the volunteers showed activity in the superfrontal gyrus — the brain region associated with self-awareness-related function.
But when the card flipping and musical sequences were rapid, there was no activity in the superfrontal gyrus, despite activity in the sensory cortex and related structures.
“The regions of the brain involved in introspection and sensory perception are completely segregated, although well connected,” says Goldberg, “and when the brain needs to divert all its resources to carry out a difficult task, the self-related cortex is inhibited.”
The brain’s ability to “switch off” the self may have evolved as a protective mechanism, he suggests. “If there is a sudden danger, such as the appearance of a snake, it is not helpful to stand around wondering how one feels about the situation,” Goldberg points out.
It is possible that research into how the brain switches self-awareness on and off will help neurologists gain a deeper understanding of autism, schizophrenia and other mental disorders where this functionality may be impaired.
Journal reference: Neuron (vol 50, p 329)
19 April 2006
Watching the brain ‘switch off’ self-awareness
via New Scientist