Driving simulator spots cognitive changes missed by standard tests

People with Parkinson’s disease may show subtle changes in their driving abilities even when standard cognitive tests appear normal, according to a study that used a driving simulator to detect impairments.

The simulator revealed slower reaction times and reduced control of lane position — an indicator of impaired visuospatial accuracy — in drivers with Parkinson’s compared with healthy drivers.

“These findings suggest that driving simulators may play a key role in improving the assessment of driving competence in [Parkinson’s disease], providing insight into real-world challenges faced by this population,” the researchers wrote. The simulator was more sensitive than conventional tests in detecting early impairments “in reaction time and visuospatial accuracy, both critical for safe driving,” they wrote.

The study, “Cognitive alterations related to driving performance in Parkinson’s disease detected by a driving simulator,” was published in Scientific Reports.

Cognitive changes among early Parkinson’s signs

Parkinson’s disease is caused by the progressive loss of the nerve cells that produce dopamine, a signaling molecule involved in motor control. While the presence of hallmark motor symptoms usually guides a Parkinson’s diagnosis, cognitive changes “including deficits in attention, executive function, and working memory” are often present from the early stages, the researchers wrote.

“These impairments not only affect cognitive performance but also influence driving behavior,” they said.

Driving requires the constant integration of attention, visual processing, and rapid reaction time, all functions that can be affected by these early cognitive changes. As a result, even subtle cognitive alterations in Parkinson’s may undermine a person’s ability to drive safely.

Standard driving assessments often fail to detect these changes because they are performed in “abstract, decontextualized environments that fail to replicate the complexity and realism of actual driving situations,” the researchers wrote.

“Driving simulators have emerged as a promising alternative, allowing for detailed and controlled measurement of key driving parameters,” they wrote.

The team recruited seven men with Parkinson’s disease who were still actively driving and seven healthy drivers matched for age and sex. All participants were enrolled and tested from March to June of 2024. The two groups did not differ in driving experience, daily distance driven, or how often they drove each week.

All participants completed a cognitive assessment comprising standard cognitive tests and computerized reaction-time tasks. This was followed by a series of realistic driving simulation tests, with all evaluations completed in a single session lasting about two hours.

The driving simulator consisted of three large screens that provided a wide field of view, along with a steering wheel and pedals that mimicked real driving. Participants completed five driving scenarios: Two involved following a lead vehicle that suddenly slowed or stopped, allowing researchers to measure reaction time and how well drivers adjusted their speed to traffic ahead. The remaining scenarios required right, left, and reverse maneuvers to assess lane keeping, steering control, and visuospatial accuracy.

Standard cognitive test scores were similar between groups, but differences emerged in driving performance.

In the simulator, Parkinson’s patients showed trends toward slower reactions, greater speed variability when following another vehicle, and poorer lane control during turns, though these differences did not reach statistical significance due to the small sample size.

Differences involving left turns were significant, however. Drivers with Parkinson’s drifted farther from the center of the lane and spent more time outside their lanes than healthy drivers, indicating reduced visuospatial accuracy.

Computerized reaction-time testing supported the findings. When participants were asked to press a button as quickly as possible when a plus symbol appeared on the screen, Parkinson’s patients showed reduced visual processing and sustained alertness.

Driving performance was significantly linked to disease severity and treatment doses. More advanced disease was associated with a poorer ability to stay in a lane during both right and left turns and with more time spent outside the lane during left turns. Higher daily doses of levodopa, a standard Parkinson’s medication, were linked to slower reaction times when following another vehicle and with greater lane deviation during left turns.

“Although the actual impact of these deficits on driving safety remains to be fully evaluated, the refinement of driving simulators — such as the one used in this experiment — represents a promising step toward improving the detection of variables that may affect driving performance in people with PD,” the researchers concluded.