Cognetics detect risk for cognitive decline in Parkinson's disease

When does a fleeting sensation of a presence become a warning sign?

Up to 60% of people with Parkinson's disease experience minor hallucinations — fleeting sensations of a presence (presence hallucination) when no one is there, or glimpsing of an undefined and moving figure at the edge of vision. Although these experiences are known to precede more complex visual hallucinations and are considered early markers of cognitive risk, standard neuropsychological assessments have repeatedly failed to detect any objective cognitive difference between patients who have minor hallucinations and those who do not.

In a new study published in the Journal of Parkinson’s Disease led by Dr. Jevita Potheegadoo, we combined clinical neuropsychological testing with a robotic procedure that determines patients’ hallucination susceptibility (by experimentally inducing presence hallucinations — the sensation of an unseen person standing nearby (Bernasconi et al., 2021; Potheegadoo et al., 2022).

First, we found that patients with minor hallucinations had significantly higher hallucination susceptibility than patients without any hallucinations. Critically, this heightened susceptibility was linked to lower performance on frontal subcortical cognitive functions such as executive control, attention, and working memory, although this relationship that was entirely absent when relying on standard testing alone. Patients with minor hallucinations also reported greater subjective cognitive difficulties in daily life.

These findings demonstrate that the robotic hallucination-induction procedure should be combined with clinical neuropsychological assessments, thereby revealing a subtle but meaningful cognitive vulnerability in early Parkinson's disease that would be missed by standard clinical tools. The present approach that links techniques from cognitive science and robotics is called cognetics (Rognini & Blanke, 2016) and offers a more sensitive method of identifying patients at risk of cognitive decline. Our current work determines the potential of cognetics for earlier cognitive decline detection and extends the approach to other neurodegenerative diseases.

This work was also presented and discussed with patients and care-givers in a dedicated webinar organised by France Parkinson on March 9^th 2026 (available here).