set refers to the process of updating or "shifting" cognitive
strategies in response to changes in the environment. For
example, in some neuropsychological
tests, patients are first asked to perform according to
some rule (e.g., given a choice between a red and a yellow
object, always choose the red object). Next, patients are
asked to switch to a new rule (e.g., always choose the larger
object, regardless of color). Successful performance requires
the ability to abandon an old strategy and start responding
according to a new rule.
Patients with damage to the frontal
are often impaired at tasks which require shifting set. They
may have difficulty abandoning the old rule -- continuing
to pick the red object even though they know their choice
is wrong -- and they may also have difficulty learning a new
rule to replace the old one.
Patients with Parkinson's disease may also
have trouble shifting set. This is because Parkinson's disease
in the substantia
nigra, a brain region that normally helps regulate function
in the frontal lobes; as the neurons in the substantia nigra
die, the frontal lobes may become somewhat dysfunctional.
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain