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Abstract:
Division of Neuroscience, Imperial College, Charing Cross
Hospital, London UK. The Wisconsin Card Sorting Test (WCST) is
widely used in patient and neuroimaging studies of cognitive
set-switching. However it is a complex task and poor performance
may be attributable to cognitive deficits other than set-switching.
We presented a simplified version of the WCST to normal individuals
using a computer touch screen. Cards presented at the bottom of the
screen (lower card) had to be matched to one of three upper cards
according to either their shape or colour. Trials were preceded by
a cue indicating the dimension to match by ("shape" / "colour").
Response times and spontaneous eye movements were recorded. The
results showed that response times and number of saccades increased
after a switch in the sorting dimension. Furthermore, saccade
trajectories were significantly biased towards cards which shared
the other stimulus dimension with the lower card. This effect
lasted for 2 trials after a switch, suggesting that the previous
set had not been fully inhibited on these trials. This result
contradicts the notion that inhibition of the previous set is a
discrete process that must be completed prior to reconfiguration of
the new task. Instead, inhibition of the preceding set is a
continuous process, lasting for several trials after a change in
set.
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