Impaired conflict monitoring in Parkinson’s disease patients during an oculomotor redirect task

Abstract

Fallibility is inherent in human cognition and so a system that will monitor performance is indispensable. While behavioral evidence for such a system derives from the finding that subjects slow down after trials that are likely to produce errors, the neural and behavioral characterization that enables such control is incomplete. Here, we report a specific role for dopamine/basal ganglia in response conflict by accessing deficits in performance monitoring in patients with Parkinson's disease. To characterize such a deficit, we used a modification of the oculomotor countermanding task to show that slowing down of responses that generate robust response conflict, and not post-error per se, is deficient in Parkinson's disease patients. Poor performance adjustment could be either due to impaired ability to slow RT subsequent to conflicts or due to impaired response conflict recognition. If the latter hypothesis was true, then PD subjects should show evidence of impaired error detection/correction, which was found to be the case. These results make a strong case for impaired performance monitoring in Parkinson's patients.

Effects of combined MAO-B inhibitors and levodopa vs. monotherapy in Parkinson’s disease

“…Our results suggest that learning impairment is exacerbated when the learning task involves uncertain feedback and response conflict, as in the probabilistic, but not deterministic, learning task. This interpretation is also in agreement with prior research showing that PD patients show impairments in conflict-based decision making tasks (Farooqui et al, 2011; Vandenbossche et al, 2012). This also points to the finding that probabilistic learning has a better potential to reveal differences in drug effects than deterministic learning tasks.…”

A common stochastic accumulator with effector-dependent noise can explain eye-hand coordination

“…One difference in our task compared with others is that hand-alone, eye-alone and eye-hand conditions for the initial eight subjects were embedded in a task which required subjects to redirect their responses to a new target on infrequent random "step" trials. Although such a context is likely to have engaged proactive inhibitory mechanisms, which would delay responses in anticipation of step trials (Chiu et al 2012;Farooqui et al 2011), such delays are expected to be a common factor across all the conditions. In addition, we observed the same pattern of RT shifts between the hand-alone and eye-hand conditions for four subjects during which EMGs were recorded (experiment 3), even though these subjects did not have to redirect their responses.…”

Response inhibition rapidly increases single-neuron responses in the subthalamic nucleus of patients with Parkinson's disease

“…Hence, deficits in post-error behavioral adjustments have been reported in PD patients compared to healthy controls (Farooqui et al, 2011) whereas converging evidences suggest that performance monitoring processes are overactive in OCD patients (Endrass, Klawohn, Schuster, & Kathmann, 2008;Ursu, Stenger, Shear, Jones, & Carter, 2003). Note that in our studies, PD patients displayed a more serious inhibitory deficit than the OCD population in our previous study (SSRT of 242 ± 64 msec in OCD patients against 312 ± 17 msec for PD patients).…”