Abstract
Non-motor symptoms like cognitive impairment are a huge burden for patients with Parkinson’s disease. We examined conflict adaptation by using the congruency sequence effect as an index of adaptation in 17 patients with Parkinson’s disease and 18 healthy controls with an Eriksen flanker task using functional magnet resonance imaging to reveal possible differences in executive function performance. We observed overall increased response times in patients with Parkinson’s disease compared to healthy controls. A flanker interference effect and congruency sequence effect occurred in both groups. A significant interaction of current and previous trial type was revealed, but no effect of response sequence concerning left or right motor responses. Therefore, top-down conflict monitoring processes are likely the main contributors leading to the congruency sequence effect in our paradigm. In both groups incongruent flanker events elicited activation in the middle temporal gyrus, inferior parietal cortex, dorsolateral prefrontal cortex and the insula in contrast to congruent flanker events. A psychophysiological interactions analysis revealed increased functional connectivity of inferior parietal cortex as a seed to the left prefrontal thalamus during incongruent vs. congruent and neutral stimuli in patients with Parkinson’s disease that may reflect compensatory facilitating action selection processes. We conclude that patients with Parkinson’s disease exhibit conflict adaptation comparable to healthy controls when investigated while receiving their usual medication.
Highlights
Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide and is marked by motor dysfunctions as well as non-motor symptoms (Schapira et al, 2017)
We are interested in whether the congruency sequence effect (CSE) emerges mainly from top-down conflict monitoring or bottom-up feature repetition, which may be disentangled by evaluating response sequences, and whether patients with PD differ from healthy controls (HC) due to impaired conflict adaptation (Botvinick et al, 1999; Rustamov et al, 2013)
Concerning the significant interaction “Current trial type * Previous trial type”, response times (RT) were faster in both groups if the current and previous trial were the same trial type, regardless of the motor response alternating or repeating left or right (Fig. 3a–d, supplementary Table 2)
Summary
Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide and is marked by motor dysfunctions as well as non-motor symptoms (Schapira et al, 2017). Brain Imaging and Behavior incongruent as compared to congruent trials This effect is referred to as “congruency sequence effect (CSE)” (Duthoo et al, 2014). The concept of conflict adaptation states that a similar level of conflict during consecutive flanker events reduces RTs (Botvinick et al, 2001) while the theory of feature repetition states that a stimulus priming effect accelerates responses to repeated stimuli and repeated motor responses (Mayr et al, 2003; Nieuwenhuis et al, 2006). We are interested in whether the CSE emerges mainly from top-down conflict monitoring or bottom-up feature repetition, which may be disentangled by evaluating response sequences, and whether patients with PD differ from HC due to impaired conflict adaptation (Botvinick et al, 1999; Rustamov et al, 2013)
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