Decreased Brain Connectivity May Be Tied to Parkinson's Hallucinations

Decreased connectivity between areas of the brain involved in attention and visual processing may contribute to the visual hallucinations often seen in people with Parkinson’s disease, according to a new Dutch study published online in the journal Radiology.

Seeing these disconnections on fMRI (functional magnetic resonance imaging) beforehand may help predict the development of visual hallucinations in Parkinson’s patients.

“Visual hallucinations in Parkinson’s disease are frequent and debilitating,” said study author Dagmar H. Hepp, M.D., from the Department of Neurology and the Department of Anatomy and Neurosciences at Vrije Universiteit (VU) University Medical Center in Amsterdam, the Netherlands.

“Our aim was to study the mechanism underlying visual hallucinations in Parkinson’s disease, as these symptoms are currently poorly understood.”

Very few studies have used fMRI to investigate visual hallucinations in patients with Parkinson’s disease, and even those studies were often limited to task-based methods involving activities that focus on visual stimulation or cognitive tasks.

In addition, the process may become complicated because the presence of visual hallucinations is strongly linked to the development of cognitive decline in Parkinson’s disease. These cognitive deficits may then negatively influence a patient’s ability to perform specific tasks during an fMRI exam.

To examine the connectivity, or communication, between brain areas, the researchers used resting-state fMRI, a method of brain imaging that can be used to evaluate patients who are not performing an explicit task.

The researchers measured brain connectivity in 15 patients with visual hallucinations, 40 patients without visual hallucinations, and 15 healthy controls by calculating the level of synchronization between activation patterns of different brain areas.

The findings show that in all patients with Parkinson’s disease, several brain areas communicated less with the rest of the brain as compared to the control group. However, in patients experiencing visual hallucinations, several additional brain areas showed this decreased connectivity with the rest of the brain, particularly in areas that play a strong role in maintaining attention and processing visual information.

“We found that the areas in the brain involved in attention and visual processing were less connected to the rest of the brain,” said study author Menno M. Schoonheim, Ph.D., from the Department of Anatomy and Neurosciences at VUMC.

“This suggests that disconnection of these brain areas may contribute to the generation of visual hallucinations in patients with Parkinson’s disease.”

While the study offers no direct therapeutic implications for patients with Parkinson’s disease, the researchers note that future studies could help determine whether stimulating these disconnected areas of the brain could help treat patients with visual hallucinations.

Source: Radiological Society of North America