Visual hallucinations in Parkinson's disease; clinical and fMRI studies

PhD ceremony: Ms. A.M. Meppelink, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Title: Visual hallucinations in Parkinson's disease; clinical and fMRI studies

Promotor(s): prof. K.L. Leenders

Faculty: Medical Sciences

Parkinson's disease (PD) is a progressive brain disease characterized by motor symptoms like tremor, slowness and stiffness. In addition, non-motor symptoms like visual hallucinations (VH) occur widely. The pathophysiological mechanism of VH is still unknown. A common view about VH is that it is an adverse effect of dopaminergic treatment for PD, but it may also relate to disease processes.In this thesis, associations were studied between impaired visual perception and brain activity in PD with VH using functional MRI (fMRI). Patients with VH were slower in recognizing images that emerged from noise, as compared to patients without VH and healthy volunteers. The researchers found that VH-associated functional defects in PD patients were not associated with gray matter volume loss, but could precede such anatomical changes. Another possible cause of the functional differences is reduction of the level of the neurotransmitter acetylcholine. Further research is necessary to evaluate whether medication can increase the levels of acetylcholine, resulting in a 'normalization' of impaired visual cortex activation in Parkinson's patients with VH.