Effects of aging, Parkinson's disease, and dopaminergic medication on response selection and control

Abstract

We examined effects of short-term and long-term dopaminergic medication in Parkinson's disease on conflict monitoring or response selection processes. These processes were examined using event-related potentials (ERPs), while subjects performed a stimulus-response (S-R) compatibility task. An extended sample of young and elderly controls, Parkinson's disease patients with a medication history (PDs) and initially diagnosed, drug-naïve de novo PD patients (de novo PDs) were enrolled. Both PD groups were measured twice (on and off-medication or before and 8 weeks after medication onset).The results show that dopaminergic intervention selectively reduced the pathologically enhanced response selection in compatible S-R relations. This medication effect was already evident after short-term treatment, not differing from long-term treatment and performance in elderly controls. Contrary, age-related attenuations of the N2 in incompatible S-R relations, probably reflecting impaired conflict processing or response control, are unaffected by medication. The results suggest that compatible and incompatible S-R relations demand different neuronal mechanisms within the basal ganglia, as only the former are affected by agonizing the dopaminergic system.

Event-related potentials and cognition in Parkinson’s disease: An integrative review

“…Following the initiation of dopaminergic medication, N2 congruency effects no longer differed from that observed in a control group, potentially indicating that dopaminergic medication might remedy altered N2 congruency effects in drug-naive PD patients (Willemssen et al, 2011; novo | post medication). Thus, the role of dopaminergic medication on N2 congruency effects in PD remains to be clarified in future studies.…”

“…Other ERP measures (N2 latencies: Praamstra et al, 1998;Rustamov et al, 2013;Willemssen et al, 2011;P3 amplitudes and latencies: Praamstra et al, 1998;Stemmer et al, 2007;Willemssen et al, 2011; but see Verleger et al, 2013) were unaltered in PD when examined in flanker tasks. Overall, the evidence suggests that electrophysiological correlates of conflict processing are unaltered in medicated PD patients.…”

“…Inspection of Table 4 reveals that N2 amplitudes in the flanker task have repeatedly been found unaltered in chronically medicated PD patients (Praamstra et al, 1998;Stemmer et al, 2007;Verleger et al, 2010;Willemssen et al, 2011). Similarly, congruency affects N2 amplitudes normally in chronically medicated PD patients, with larger N2 amplitudes elicited on incongruent compared to congruent trials (Rustamov et al, 2013).…”

“…However, one study found attenuated N2 amplitudes on incongruent trials in asymptomatic (and hence non-medicated) carriers of Parkin or PINK1 mutations who are considered to represent pre-clinical PD patients (Verleger et al, 2010). In a similar vein, Willemssen et al (2011;de novo | pre medication) found diminished N2 congruency effects in a group of newly diagnosed, drug-naive PD patients.…”

“…Thus, the role of dopaminergic medication on N2 congruency effects in PD remains to be clarified in future studies. In particular, the effects of medication should be disentangled from learning effects; these two factors were (necessarily) confounded in the study by Willemssen et al (2011) in which the patients were always drug-naive at initial testing, and always medicated at subsequent testing.…”