| |
Abstract:
The binding stimulus input to response selection is
influenced by dopamine in the basal ganglia, which is severely
depleted in Parkinson's Disease (PD). We studied 25 PD and 17
healthy control (HC) subjects on an ignored repetition task
requiring subjects to select a cued shape from a display containing
a distractor and target (prime). On subsequent (probe) trials,
subjects again selected a cued shape, but the shape was matched to
the prime distractor shape or location. Negative priming (NP) was
defined as the slowing in probe trials associated with properties
of the prime distractor. Overall, NP effects in PD were larger than
in HC. Partitioning the probe responses into pre-movement and
movement time components revealed an interesting pattern of new
results. In HC, pre-movement times to distractor locations were
unaffected, while the NP effect was entirely carried by slowing of
the movement component. In PD, both pre-movement and movement times
contributed to the large location NP effects. For distractor shape,
HC had shorter pre-movement but longer movement times, canceling
the effect of NP to shape. In PD, distractor shape had no effect on
pre-movement times, but movement time was associated with NP to an
even greater degree than in HC. These results suggest that
alterations of neurochemistry in PD may reduce efficiency in
processing distractor stimuli, and that initiation (pre-movement)
and executional (movement) components of response selection are
differentially affected.
|
