Our grip on reality is slim...

Our Grip On Reality Is Slim, Says University College London Scientist
The neurological basis for poor witness statements and hallucinations
has been found by scientists at UCL (University College London). In
over a fifth of cases, people wrongly remembered whether they actually
witnessed an event or just imagined it, according to a paper published
in NeuroImage this week.

Dr Jon Simons and Dr Paul Burgess led the study at the UCL Institute of
Cognitive Neuroscience. Dr Burgess said: "In our tests volunteers
either thought they had imagined words which they had actually been
shown or said they had seen words which in fact they had just imagined
- in over 20 per cent of cases. That is quite a lot of mistakes to be
making, and shows how fallible our memory is - or perhaps, how slim our
grip on reality is!

"Our work has implications for the validity of witness statements and
agrees with other studies that show that our mind sometimes fills in
memory gaps for us, and we confuse what we imagined occurred in a
situation - which is related to what we expect to happen or what
usually happens - with what actually happened.

"Most of us, though, have a critical reality monitoring function so
that we are able to distinguish well enough between what is real and
what is imagined and our imagination does not have too great an impact
on our lives - unless the reality check system breaks down such as
after stroke or in cases of schizophrenia."

The study found that the areas that were activated while remembering
whether an event really happened or was imagined in healthy subjects
are the very same areas that are dysfunctional in people who experience
hallucinations.

Dr Burgess said: "We believe that hallucinations are caused by a
difficulty in discriminating information present in the outside world
from information that is imagined. In schizophrenia the difficulty you
have in separating reality from imagined events becomes exaggerated so
some people have hallucinations and hear voices that simply aren't
there." These results indicate a link between the brain areas
implicated in schizophrenia and the regions that support the ability to
discriminate between perceived and imagined information.

In the tests, healthy subjects were shown 96 well-known word pairs from
pop culture such as 'Laurel and Hardy', 'bacon and eggs', and 'rock and
roll'. The participants were asked to count the number of letters in
the second word of the pair. Often the second word wasn't actually
shown and the subject had to imagine the word - such as 'Laurel and
?'.

Participants were then asked which of the second words they had
actually seen on screen and which ones they had only imagined. The
subjects' brain activity was observed using fMRI scans while they
remembered whether words had been imagined or seen on screen.

When people accurately remembered whether they had actually seen a word
or just imagined it brain activity in the key areas increased - many
of which are found in brain area 10, which is involved in imagination
and reality checking, develops last in the brain and is twice as big in
humans as in other animals. In the people who did not remember
correctly, activation in brain area 10 was reduced.

Source: University College London
http://www.sciencedaily.com/releases/2006/06/060623215216.htm

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