Flanker compatibility effects in patients with Parkinson's disease: impact of target onset delay and trial-by-trial stimulus variation

Abstract

Parkinson's disease (PD) patients and healthy controls were administered a flanker task that consisted of the presentation of colored targets and distractors. Participants were required to attend to the center target and identify its color. The stimulus displays were either congruent (i.e., the target and flankers were the same color) or incongruent. The time between the onset of the flanker and the target color (the target onset delay) was either short or long. Results indicated that PD patients and controls did not differ in the magnitude of the flanker effect within individual trials in that both groups demonstrated a typical flanker effect at the short target onset delay and neither group demonstrated a flanker effect at the longer delay. However, when performance was examined on a trial-by-trial basis, PD patients demonstrated a slowing of reaction time relative to controls when having to make the same response across consecutive trials at longer inter-trial intervals when the flankers were incongruent across consecutive trials and the display on the second of two trials was incongruent. These results indicate that PD patients are impaired in inhibiting the distractors over an extended delay and that this deficit may impact motor responding in these patients, suggesting that the basal ganglia contribute to the interface of attention and action.

Figure 1

Sequence of stimuli presentation and target onset delay.

Figure 2

Mean reaction times for congruent and incongruent trials at the short target onset delay (TOD) and the long target onset delay (TOD) for the PD patients and NC participants. Error bars represent the standard error of the mean (SEM).

Figure 3

Grouping of n-1 and n couplets for trial-by trial analysis where n-1 trial is congruent. Black “O”s represent green targets and white “O”s represent red targets. Grey “O”s represent the onset of the target location on the n couplet before it changes to one of the two target response colors. Note, timing of the trials are not depicted nor are fixation crosses or blank screens.

Figure 4

Mean of median reaction times for trial-by-trial flanker effects for repetition priming (RP), response change- congruent (RC-C), no response change- incongruent (NRC-I), and response change- incongruent (RC-I) couplets. Error bars represent the standard error of the mean (SEM).