Visuospatial attention to single and multiple objects Is independently impaired in Parkinson's disease
Norton, D. J.; Nguyen, V. A.; Lewis, M. F.; Reynolds, G. O.; Somers, David C.; Cronin-Golomb, Alice
Parkinson’s disease (PD) is associated with deficits in visuospatial attention. It is as yet
unknown whether these attentional deficits begin at a perceptual level or instead reflect disruptions
in oculomotor or higher-order processes. In the present study, non-demented individuals
with PD and matched normal control adults (NC) participated in two tasks requiring
sustained visuospatial attention, both based on a multiple object tracking paradigm. Eye
tracking was used to ensure central fixation. In Experiment 1 (26 PD, 21 NC), a pair of identical
red dots (one target, one distractor) rotated randomly for three seconds at varied
speeds. The task was to maintain the identity of the sole target, which was labeled prior to
each trial. PD were less accurate than NC overall (p = .049). When considering only trials
where fixation was maintained, however, there was no significant group difference, suggesting
that the deficit’s origin is closely related to oculomotor processing. To determine
whether PD had additional impairment in multifocal attention, in Experiment 2 (25 PD, 15
NC), two targets were presented along with distractors at a moderate speed, along with a
control condition in which dots remained stationary. PD were less accurate than NC for
moving (p = 0.02) but not stationary targets. This group difference remained significant
when considering only trials where fixation was maintained, suggesting the source of the
PD deficit was independent from oculomotor processing. Taken together, the results implicate
separate mechanisms for single vs. multiple object tracking deficits in PD.
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