Exploring characteristics of visual search in older adults and people with Parkinson's during adaptive gait.

Freezing of gait is a disabling episodic symptom of Parkinson's disease, typically emerging during complex locomotor tasks such as turning, obstacle negotiation, and gait initiation. These tasks require effective motor planning and proactive visual search of the intended walking route. Current evidence suggests that people with Parkinson's disease and freezing of gait show different patterns of visual search compared to those without freezing of gait and healthy older adults. However, existing reports are based on relatively simple tasks that lack common triggers for freezing of gait and do not adequately control for other factors likely to influence visual search, such as motor symptom severity and balance ability. This study examined visual search behaviour in 24 healthy older adults and 37 people with Parkinson's disease (21 with freezing of gait, 16 without) during a complex walking task requiring repeated turning and navigation through narrow spaces. Visual search characteristics were compared between people with Parkinson's disease and healthy controls, and relationships between visual search, freezing of gait, motor symptom severity, and balance ability were explored within the Parkinson's disease group. Compared with healthy controls, people with Parkinson's disease showed significantly fewer fixations toward areas outside the walking path, longer average fixation durations, and reduced saccade amplitudes, with no differences in proactive visual planning of the intended route. No relationship was found between visual search outcomes and freezing of gait. Reduced fixations to outside-path areas were associated with poorer functional balance independently of motor symptom severity. These findings indicate that restricted visual sampling in Parkinson's disease is primarily associated with balance impairment rather than freezing of gait or motor symptom severity.