After the computerised snub, the scan detected activity in an
area of the brain linked to physical pain.
Experts say the study, from the journal Science, is a hint to
the importance the brain places on social ties.
The researchers involved in the study, from the University of
California at Los Angeles, used an MRI scanner to probe the brains
of their test subject as their feelings were manipulated.
These scanners can detect subtle changes in blood flow to various
parts of the brain - which indicate when the region is active.
To provoke the right response, they devised an ingenious computer
simulation designed to be reminiscent of a playground game.
The participants were shown a screen which gave the appearance
of a "ball-throwing" game involving both the volunteer and two
other figures, represented by animated characters.
Psychological pain in humans,
especially grief and intense loneliness, may share some of the
same neural pathways that elaborate physical pain
Dr Jaak Panksepp, Bowling Green State University, Ohio
The test subjects were
told that real people were controlling the other two "people",
and the game took the form of throwing the ball in turn between
all three of them.
Of course, this was an elaborate hoax - there were no other
human players, and the other characters in the game were controlled
entirely by the computer.
At first, the game proceeded as it should, with the ball coming
at regular intervals to the player controlled by the human volunteer.
Mean machine
However, after a while, the two
computer controlled characters started throwing the ball only
to each other, apparently excluding the test subject from the
game.
It was at this point that the
brain reactions were measured by the scanner.
The researchers noticed one key
area of the brain "lighting up" on the scan when this happened.
This area, the anterior cingulate
cortex, is already known to be associated with the brain's response
to the unpleasant feelings linked to physical pain.
This was not just a frustrated
reaction to not being able to play - researchers had already
tested this by having a short period at the start of the game
in which the controls appeared not to work properly.
The researchers wrote: "Evidence
suggests that some of the same neural machinery recruited in
the experience of pain may also be associated with social separation
or rejection."
Powerful feelings
Dr Jaak Panksepp, from the Centre
for Neuroscience, Mind and Behavior at Bowling Green State University
in Ohio, said that feelings of social exclusion were powerful
instincts in animals and humans.
He said: "The feelings induced
by experimental games in the laboratory, are a pale shadow of
the real-life feelings that humans and other animals experience
in response to the sudden loss of social support.
"Psychological pain in humans,
especially grief and intense loneliness, may share some of the
same neural pathways that elaborate physical pain.
"Given the dependence of mammalian
young on their caregivers, it is hard not to comprehend the
strong survival value conferred by common neural pathways that
elaborate both social attachment and the affective qualities
of physical pain."
