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Gaze Behaviours and Visual Perception in Parkinson’s disease – Integrity of the Dorsal Visual Processing Stream and the Role of the Zona Incerta
Negotiating dynamic obstacles and apertures safely depends fundamentally on the integrity of our visual processing system, which revolves around the way we observe, perceive and interact with our environment. Individuals with Parkinson’s disease (PD) can display deficits in eye movements and even perceptual alterations, yet little is known about the implications of such deficiencies on the way they navigate during daily living. When the commonly employed PD treatment options involving medications have been exhausted, deep brain stimulation (DBS) surgery is often offered by neurosurgical teams to treat the symptoms. The zona incerta (Zi) is an alternative brain site that is used in DBS for treating PD. Animal studies suggest that the Zi is involved in controlling eye movements, but the role of the human Zi on gaze behaviours, along with its influence on perception and visuo-locomotor behaviours are unknown.
This research therefore aims to gain further insights into the integrity of the dorsal visual neural pathway that oversees motion and spatial perception in individuals with PD from a functional perspective, through dynamic obstacle avoidance and aperture crossing tasks respectively. This study also aims to assess the role of the Zi in eye movement control, perception and visuo-locomotor integration in people with PD undergoing DBS surgery.
This is the first study that extensively measures gaze behaviours in people with PD to foster our understanding on visual perception-action coupling during functional locomotor activities of daily living (ADL). Through the use of novel, three-dimensional stereoscopic visual stimuli for dynamic obstacle avoidance and a classic aperture crossing task, the findings from this research have significant implications for preventing falls and freezing of gait in individuals with PD. Moreover, one of the primary goals of DBS intervention is to improve the recipients’ quality of everyday living. With the construct of this research designed to reflect locomotor ADL, the objective findings may serve to better inform neurosurgeons about their choice of an unconventional brain target (i.e. Zi) used in treating PD.