By Amy Norton

HealthDay Reporter

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

The study focused on Parkinson’s patients who present with hallucinations of presence, a false feeling that another person is nearby.

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

This, in turn, allowed them to map brain activity that appeared to be underlying the hallucinations, including interrupted connections in parts of the frontal and temporal lobes of the brain.

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

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


Right now, the diagnosis usually depends on patients explaining their hallucinations to their doctors, which many are hesitant to do.

So the problem is misdiagnosed, said Fosco Bernasconi, one of the study’s researchers.

“Our robotic procedure offers the opportunity to investigate specific hallucinations in real time and in a fully controlled environment and conditions,” said Bernasconi, a senior scientist at the École Polytechnique Fédérale in Lausanne, Geneva.

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

It involves an abnormal accumulation 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 are movement-related, such as tremors, stiff limbs, and coordination problems.

“But Parkinson’s is complex. It’s much more than a movement disorder,” said James Beck, scientific director of the nonprofit Parkinson’s Foundation.

The disease is a brain, Beck explained, and can cause symptoms ranging from memory and thinking problems, to depression and anxiety, to speech, vision and smell deficiencies.


In addition, there are the symptoms of psychosis, which, according to Beck, is a “hard word” to digest. Hallucinations fall into this category, but issues such as presence hallucinations are considered “mild”.

“People are aware they have them,” Beck said. “They’re completely compelling.”

A patient involved in the new research, Joseph Rey of Geneva, began to have hallucinations of presence after being operated on for Parkinson’s. He would have the recurring feeling that he was accompanied by one or more people, behind or beside him.

Rey, however, was not bothered.

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

Another patient, Maurizio De Levrano of Martigny, Switzerland, experienced hallucinations of presence, which felt like the “ghost of my mother,” in addition to visuals.

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


Visual hallucinations are more common in Parkinson’s than the type of presence, Beck said. Again, people can get upset about 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 Parkinson’s medication or in interactions between different medications a patient takes.

In these cases, Beck said, it might be possible to adjust a medication. There are also two medications, clozapine and pimavanserin, that can be prescribed to relieve hallucinations.

The new research involved 26 Parkinson’s patients who underwent robotic testing. Each patient was asked to make repeated “puncture” gestures, 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 found, was able to provoke hallucinations of presence.

The phenomenon occurred even in patients who did not experience hallucinations in daily life, but was more intense in those who did.


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

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

He noted that hallucinations can boast of more severe symptoms of psychosis, including delusions, in which people believe false things.

Therefore, it is important to remove the “stigmas” around hallucinations, Beck said, and patients and doctors talk about it.

More information

The Parkinson’s Foundation has more advantages 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 City; Scientific translational medicine, April 28, 2021, online


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