Risky choices link the subthalamic nucleus with pathological gambling in Parkinson's disease

Short- and long-term cognitive effects of deep brain stimulation in the caudal zona incerta versus best medical treatment in patients with Parkinson's disease

OBJECTIVE

A growing number of studies are showing positive effects of deep brain stimulation (DBS) in the caudal zona incerta (cZi) in various tremor disorders, as well as motor symptoms of Parkinson's disease (PD). The focus of the present study was to evaluate short- and long-term cognitive effects of bilateral cZi DBS in patients with PD.

METHODS

Twenty-five nondemented patients with advanced PD were recruited to participate in a randomized trial of cZi DBS versus best medical treatment (BMT). The patients in the BMT group were offered surgery after 6 months. Neuropsychological evaluations focusing on assessing verbal and visuospatial memory, attention, and executive function were conducted at baseline and at 6 and 24 months after surgery. Self-reported measures of depression, anxiety, and change in "frontal" behaviors were also completed at all assessment points.

RESULTS

Bilateral cZi DBS in patients with PD generated few adverse cognitive effects. At the short-term follow-up after 6 months, no differences were found between patients randomized to BMT and patients randomized to DBS with regard to most of the cognitive domains assessed. A transient improvement in anxiety was, however, found in the surgical group. At the long-term follow-up 24 months after cZi DBS, no major changes in global cognitive functioning were found, although a decline in attention and self-reported executive function was noted.

CONCLUSIONS

With the exception of a decline in attention and self-reported executive function, bilateral cZi DBS for PD in appropriately screened patients appears to be generally safe with regard to cognitive function, both in the short- and long-term perspective.

Mood and behavioural effects of subthalamic stimulation in Parkinson's disease

Deep-brain stimulation (DBS) of the subthalamic nucleus (STN) is an established treatment for motor complications in Parkinson's disease. 20 years of experience with this procedure have contributed to improved understanding of the role of the STN in motor, cognitive, and emotional control. In Parkinson's disease, the pathological STN neuronal activity leads to motor, cognitive, and emotional inhibition. Deafferentation of the STN by DBS can reverse such behavioural inhibition. The release of this brake allows both motor and non-motor improvement, but can also be associated with excessive motor, cognitive, and emotional behavioural disinhibition. Conversely, the notable reduction in anti-parkinsonian drug dose allowed by motor improvement can unveil mesolimbic hypodopaminergic behaviours such as apathy, anxiety, or depression. Fine-tuning of stimulation parameters with dopaminergic drugs is necessary to prevent or improve pathological behaviours.

Effects of deep brain stimulation of the subthalamic nucleus on inhibitory and executive control over prepotent responses in Parkinson's disease

Inhibition of inappropriate, habitual or prepotent responses is an essential component of executive control and a cornerstone of self-control. Via the hyperdirect pathway, the subthalamic nucleus (STN) receives inputs from frontal areas involved in inhibition and executive control. Evidence is reviewed from our own work and the literature suggesting that in Parkinson's disease (PD), deep brain stimulation (DBS) of the STN has an impact on executive control during attention-demanding tasks or in situations of conflict when habitual or prepotent responses have to be inhibited. These results support a role for the STN in an inter-related set of processes: switching from automatic to controlled processing, inhibitory and executive control, adjusting response thresholds and influencing speed-accuracy trade-offs. Such STN DBS-induced deficits in inhibitory and executive control may contribute to some of the psychiatric problems experienced by a proportion of operated cases after STN DBS surgery in PD. However, as no direct evidence for such a link is currently available, there is a need to provide direct evidence for such a link between STN DBS-induced deficits in inhibitory and executive control and post-surgical psychiatric complications experienced by operated patients.