Abstract
Objective: This study investigated selective attention in people with Parkinson’s disease (PD) using the Priming-of-Popout (PoP) paradigm. Background: Attentional deficits have been previously reported in PD. The aim of this study was to investigate attentional deficits in PD with a new experimental Priming-of-Popout (PoP) paradigm that controlled for response selection deficits as a confounding variable, rarely done in previous studies. Methods: 12 nondemented and non-depressed PD patients (6466.5years, self-assessed Hoehn &Yahr: 2.4 (range:1-3.5)) and 12 age-matched controls (6365.7years) participated. The PoP paradigm is a speeded reaction time task, and the participants were instructed to respond to the shape of an odd coloured target (singleton) while ignoring three distractors displayed in another second colour. By design, this task is well- suited to examine attentional pop-out effects, because it is possible to disambiguate the effect of colour, which is an attention-driven feature, from the effect of shape, which defines a specific response. There were two conditions in the experiment. In one (mixed) condition, the singleton colour varied randomly being either red or green. In the other (pure) condition, the participant was told at the beginning of the block which singleton colour (e.g. red) would occur throughout the entire block. We predicted that the RT difference between the mixed and the pure conditions would be greater for PD patients than age-matched controls. Furthermore, in the mixed condition, group differences in colour repetition/alternation effects were investigated. Results: PD patients were generally slower in performing the PoP task (p<.015). Both controls and PD patients had increased reaction times in the mixed compared to the pure condition. The difference between these two conditions was 62ms larger in the PD than in the control group, and this group difference was marginally significant (p<.08). No difference was found between PD patients and controls when comparing colour repetition and alternation in the mixed condition. Conclusions: These preliminary results suggest that selective attention deficits may be present in PD, even after controlling for the confounding effects of response selection.