Deficits in inhibitory control and conflict resolution on cognitive and motor tasks in Parkinson’s disease

Abstract

Recent imaging studies in healthy controls with a conditional stop signal reaction time (RT) task have implicated the subthalamic nucleus (STN) in response inhibition and the pre-supplementary motor area (pre-SMA) in conflict resolution. Parkinson's disease (PD) is characterized by striatal dopamine deficiency and overactivity of the STN and underactivation of the pre-SMA during movement. We used the conditional stop signal RT task to investigate whether PD produced similar or dissociable effects on response initiation, response inhibition and response initiation under conflict. In addition, we also examined inhibition of prepotent responses on three cognitive tasks: the Stroop, random number generation and Hayling sentence completion. PD patients were impaired on the conditional stop signal reaction time task, with response initiation both in situations with or without conflict and response inhibition all being significantly delayed, and had significantly greater difficulty in suppressing prepotent or habitual responses on the Stroop, Hayling and random number generation tasks relative to controls. These results demonstrate the existence of a generalized inhibitory deficit in PD, which suggest that PD is a disorder of inhibition as well as activation and that in situations of conflict, executive control over responses is compromised.

Subthalamic nucleus activity dissociates proactive and reactive inhibition in patients with Parkinson's disease

“…The SSRT was on average 402 ± 22 ms and the mean SSD was 227 ± 28 ms. Our behavioral results are compatible with the assumption of go and stop processes independence (Logan et al, 1984), because reaction times measured during GO trials did not correlate with patient's SSRT (r(11) = 0.47, p = 0.123) and reaction times during Unsuccessful STOP trials were significantly shorter than reaction times during GO trials (ANOVA: F(11,3) = 21.53, p b 0.0001; Tukey post-hoc test p = 0.0001). Overall, patients accurately performed the modified SST and behavioral performances were similar to those observed in previous studies with PD patients (Gauggel et al, 2004;Obeso et al, 2011;Ray et al, 2009). …”

Deep Brain Stimulation of the Subthalamic Nucleus, but not Dopaminergic Medication, Improves Proactive Inhibitory Control of Movement Initiation in Parkinson's Disease

“…The third clue was provided by clinical investigations showing that PD patients are generally found to be dysfunctional on measures of response inhibition [21], supporting the view that executive control over responses is compromised in PD [22,23]. However, inconsistent observations are reported regarding the nature of this broad deficit: While some authors found that PD patients have difficulties inhibiting an ongoing reaction [22,24,25], others suggested an enhancement instead of an impairment of inhibitory control [26]. We assume that these inconsistencies are partly due to the fact that current models of inhibitory control of responses, and derived psychophysical methods, are incomplete and unable to evidence important executive mechanisms ignored so far.…”

Theta burst magnetic stimulation over the pre-supplementary motor area improves motor inhibition

“…The conditional stop signal task [4,24,25] allows measurement of (i) how successfully and quickly a participant can inhibit a response when a stop signal is presented (reactive inhibition) and (ii) the extent that participants engage in proactive inhibition i.e. slowing their responses in anticipation of a stop signal (proactive inhibition) (iii) the extent of slowing of response initiation under conditions of conflict or "conflict induced slowing".…”