Cognitive dysfunction in non-demented Parkinson's disease patients: controlled and automatic behavior

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Parkinson's disease (PD) is associated with cognitive impairments affecting both automatic and controlled information processing.
• Executive functions, crucial for planning and regulating behavior, are often cited as impaired in PD patients.
• The role of the striatum in modulating automatic and controlled processes is significant, particularly in skill learning.

Purpose of the Study:

• To critically evaluate the evidence for impaired automatic and controlled information processing in non-demented Parkinson's disease (PD) patients.
• To determine the extent to which observed executive function limitations in PD are a direct consequence of impaired executive functions versus secondary effects of impaired automatic processing.
• To reassess studies on executive functioning in PD, specifically examining the control for automaticity deficits.

Main Methods:

• A comprehensive mental schema framework of executive functioning was utilized.
• Studies investigating executive functioning in non-demented PD patients were critically assessed.
• Emphasis was placed on evaluating the degree to which studies controlled for impaired automaticity.

Main Results:

• PD patients exhibit difficulties in applying and achieving automaticities, often maintaining cortical control instead of transitioning to striatal control.
• Evidence for impaired cognitive flexibility and working memory in PD is convincing, as deficits persist even in tasks with low automatic processing demands.
• Impairments in other executive functions like monitoring, inhibition, and planning are not conclusively demonstrated in non-demented PD patients and may be influenced by factors like fatigue and medication.

Conclusions:

• Observed executive function deficits in non-demented PD patients are not uniformly indicative of direct impairment in these functions.
• Cognitive flexibility and working memory deficits are the most reliably demonstrated executive impairments in PD.
• Limitations in other executive functions may be indirect effects of impaired automatic processing or influenced by confounding factors such as treatment and fatigue.