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| Scientists take first steps towards
understanding cognitive control Lancet 2000; 355: 2053 - 2060
A brain imaging study, carried out by researchers at the University
of Pittsburgh, PA, USA, has shown which regions of the frontal
lobes are activated during the Stroop task--the most widely studied
selective attention task in cognitive psychology.
This deceptively simple test requires individuals to name the
colour of ink of printed words which themselves are the names
of colours. This is much more difficult when the colour of the
word and its meaning are different; for example when the word
"red" is written in blue ink (see picture). According to Cameron
Carter, one of the authors of the study, "this is because reading
a word is automatic, such that the incorrect response (the word)
and the correct response (its colour) compete with one another".
The latest study examined two different areas of the frontal lobes
(the dorsolateral prefrontal cortex [DLPFC] and the anterior cingulate
cortex [ACC]) in 12 healthy individuals perfoming the Stroop task
(Science 2000; 288: 1835-38 ).
"The left DLPFC showed increased activity when subjects were instructed
that they were going to have to colour name, rather than read,
an upcoming Stroop stimulus", explains Carter. "The increase in
DLPFC activity was strongly correlated with how well they performed
the task." In contrast, ACC activity only increased when individuals
actually named the colour of conflicting stimuli, with this activation
being strongest in individuals who performed poorly. "This suggests
that this frontal region monitors for cognitive conflict, signaling
when attention needs to be more strongly engaged to maintain performance",
explains Carter.
"The big problem is to specify the precise function of these two
areas in cognitive terms. I think we have a long way to go before
this is achieved, but this is precisely the kind of study that
is needed to make progress" comments Chris Frith (Institute of
Neurology, London, UK). |
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