New Insights Into Parkinson’s Hallucinations

By Amy Norton
HealthDay reporter

MONDAY May 3, 2021 (HealthDay News) – Parkinson’s disease is widely considered a movement disorder, but it can cause a range of symptoms, including hallucinations. Now, a new study has shed light on what goes on in the brain during these disturbances.

The study focused on Parkinson’s disease patients who have so-called presence hallucinations – a false sense that another person is nearby.

The researchers found that they were able to induce hallucinations in a group of Parkinson’s disease patients using a fairly simple “robot ghost test” – which involved a robotic arm that touched the patient’s back.

This, in turn, allowed them to map the brain activity that seemed to underlie the hallucinations – including interrupted connections in parts of the frontal and temporal lobes of the brain.

Experts said the results – reported on April 28 in the newspaper Scientific translational medicine – could lead to a better understanding of hallucinations in Parkinson’s disease.

One possible hope, the researchers said, is to develop an objective way to diagnose and delve into each patient’s hallucinations.


Currently, the diagnosis usually depends on whether patients talk to their doctor about their hallucinations – which many are reluctant to do.

The problem is therefore underdiagnosed, said Fosco Bernasconi, one of the researchers in the study.

“Our robotic procedure offers the possibility of studying specific hallucinations in real time and in a fully controlled environment and conditions,” said Bernasconi, principal investigator at the Ecole Polytechnique Fédérale de Lausanne in Geneva.

Parkinson’s disease affects nearly one million people in the United States alone, according to the Parkinson’s Foundation.

This is an abnormal buildup of a protein called alpha-synuclein in the brain. Over time, the brain loses cells that produce dopamine, a chemical that helps regulate movement and emotional responses.

The most visible symptoms of Parkinson’s disease are related to movement – such as tremors, stiff limbs, and problems with coordination.

“But Parkinson’s disease is complex. It’s more than a movement disorder, ”said James Beck, Scientific Director of the Parkinson’s Nonprofit Foundation.

The disease is a disease of the brain, Beck explained, and it can cause symptoms ranging from problems with memory and thinking, to depression and anxiety, to impaired speech, vision and speech. ‘smell.


Then there are the symptoms of psychosis – which, Beck noted, is a “hard word” for people to digest. Hallucinations fall into this category, but problems such as presence hallucinations are considered “mild”.

“People know they have it,” Beck said. “They are completely convincing.”

A patient involved in the new research, Joseph Rey from Geneva, began hallucinating presence after undergoing surgery for Parkinson’s disease. He would have the recurring sensation of being accompanied by one or more people, either behind him or by his side.

Rey wasn’t bothered by it, however.

“I call them my guardian angels,” he said. “They don’t hurt me. They follow me everywhere. It’s reassuring in a way, because I’m not alone.”

Another patient, Maurizio De Levrano from Martigny, Switzerland, experienced hallucinations of presence – what looked like “my mother’s ghost” – as well as visual hallucinations.

“I see kinds of spiders falling from the ceiling out of the corner of my eye,” he said. “I know full well they’re not there, but instinctively I always have to turn around and look.”


Visual hallucinations are more common in Parkinson’s disease than in the presence type, Beck said. Again, people may not be bothered by them.

“But it’s still important to let your doctor know,” Beck said.

On the one hand, he explained, hallucinations are sometimes related to changes in drugs for Parkinson’s disease or interactions between different drugs that a patient is taking.

In those cases, Beck said, it might be possible to adjust a drug. There are also two drugs – clozapine and pimavanserin – that can be prescribed to relieve hallucinations, he noted.

The new research involved 26 Parkinson’s disease patients who underwent the robotic test. Each patient was asked to make repeated gestures of “pricking”, while a robotic arm mimicked the gesture on the patient’s back. Sometimes the human and the robot were out of sync in their gestures – and this, the researchers said, could trigger presence hallucinations.

The phenomenon occurred even in patients who did not experience hallucinations in everyday life – but it was more intense in those who did.


In separate studies of 30 additional patients and a group of healthy adults, Bernasconi’s team used MRI scans to see how patterns of brain activity were related to presence hallucinations.

“Hopefully,” Beck said, “this will allow for more investigation to better understand these hallucinations, and possibly lead to new therapies.”

Hallucinations, he noted, can portend more serious symptoms of psychosis, including delusions – where people believe things that are not true.

So it’s important that the “stigma” around hallucinations is lifted, Beck said, and that patients and doctors talk about it.

More information

The Parkinson’s Foundation has more on the symptoms of psychosis.

SOURCES: Fosco Bernasconi, PhD, senior scientist, École Polytechnique Fédérale de Lausanne, Geneva, Switzerland; James Beck, PhD, senior vice president, scientific director, Parkinson’s Foundation, New York; Scientific translational medicine, April 28, 2021, online

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