Parkinson's disease: neuroimaging and clinical studies on cognition and depression

Abstract

Parkinson’s disease (PD) is a movement disorder which is caused by a degeneration of dopamine producing neurons. The disease is characterized by motor symptoms, such as bradykinesia, tremor and rigidity however, cognitive impairments and depression are often present. Cognitive impairments can be found in both automatic and controlled processing. Automatic processing takes advantage of previously established and learned behavioral patterns, while controlled processing is needed in new situations in which previously established and learnt behavioral patterns are not sufficient. The studies included in this thesis investigate cognitive functioning and depression in PD using neuroimaging and clinical methods. Our studies show that the symptoms of PD in the motor, cognitive and emotional domains are associated or overlap. These associations occur both within domains of impairment as well as between domains of impairment. Within the motor domain and the domain of cognition PD patients show deautomatisation and difficulties learning new skills or automaticities. PD patients however, compensate by showing an increased reliance on controlled processing and a decreased reliance on automatic processing. Depression is another domain of impairment in PD. Depression may have a negative influence on cognition in PD. However, both cognitive impairments and motor symptoms can also influence the assessment of depression in PD, since these cognitive impairments and motor symptoms can be part of both PD and primary depression. The diagnosis of depression in PD therefore needs to be carefully considered.