Impaired visual search common in drivers with PD

Drivers with Parkinson's Disease have impaired visual search while driving, and the increased cognitive load of identifying landmarks and traffic signs worsens their driving safety, according to a recent report.The authors of the report note, "...drivers with neurological conditions that affect cognition may not perceive critical roadside information even in the absence of a measurable field defect..." They say roadside information such as landmarks provide cues for navigation, and traffic signs provide safety-relevant information. Driver safety may be affected when this information is missed.The study assessed the ability of 79 drivers with PD to search and recognise roadside landmarks and traffic signs while driving along a four-lane commercial strip. All participants in their study were community-dwelling, independently-living and licensed active drivers. Their ability to identify the roadside targets and the number of at-fault driving safety errors made during the test were compared with the results of the same test in 151 neurologically-normal older adults. The road test was conducted in a vehicle adapted with hidden instrumentation and sensors to record such aspects of driving as lane position, speed, and acceleration. Miniature cameras videotaped the drivers' lane tracking and driving behaviour. The drive lasted approximately 45 minutes and was conducted during "on" time in the PD patients. Drivers were asked to look for and report particular traffic signs and restaurants during the drive.The drivers with PD identified significantly fewer landmarks and traffic signs and made more safety errors than control subjects. However, there was a lack of significant correlation between safety errors and target identification rates, which the authors say suggests that the drivers did not prioritise the target identification task at the expense of safety.Measures of visual speed of processing and attention and visuospatial abilities were associated with target identification rates, and measures of cognitive flexibility was the only independent predictor of safety errors in drivers with PD. The authors note that a subset of drivers with PD performed well on the test, suggesting that some individuals with PD remain good drivers, but they add, "However, a substantial portion of PD patients experience development of progressive cognitive and visual deficits that can impair driving."Reference...