Deep brain stimulation for optimal visual search strategy in Parkinson's Disease

About This Grant

PROJECT SUMMARY Parkinson's Disease (PD) constitutes a prevalent neurodegenerative condition affecting approximately 10 million individuals on a global scale. The disorder engenders a range of visual deficits that encompass abnormal eye movements, including fixational saccades — essential for sustaining retinal sensitivity during prolonged fixation — and non-fixational saccades, pivotal for efficient scanning during visual search tasks. The visual navigation impairments in PD transcend mere eye movement dysfunction. They manifest as an impairment in higher visual function, such as the complex interplay of top-down process such as visual reaction time and adaptation of prior knowledge based on contextual cues – referred to as contenxutal visual priors. This constellation of issues results in hindrances across activities such as driving, reading, walking, and navigating through the surrounds – that is impaired visuo-spatial navigation. Despite the far-reaching effects of PD on visual function, treatment options remain limited. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) emerges as a promising PD treatment, particularly for motor symptoms, but its impact on visual navigation remains unclear. The strategic location of the STN near pathways controlling higher-order visual behavior, coupled with its connectivity to the cerebellum and higher order visual areas, enables the modulation of visuo- spatial navigation through the control of saccades and higher-order visual processing. This study hypothesizes that bilateral STN DBS enhances fixational and non-fixational saccades and higher-order visual processing, crucial for visual search and navigation in PD. It suggests that improved saccadic eye movement control relates to active electrode contact near the dorsal STN region and activation of cerebello-thalamic pathway, while better higher-order visual processing correlates with modulation of ansa lenticularis and lenticular fasciculus. Aim 1 focuses on evaluating if STN DBS enhances saccades to target visual navigation issues and identifies STN regions associated with these enhancements. This is done through non-invasive video oculography, measuring eye movement parameters during visual search tasks with STN DBS on and off. Additionally, imaging and DBS modeling guide the identification of beneficial STN regions for saccades. Aim 2 addresses whether STN DBS enhances visual reaction time and contextual priors. This aim investigates whether active electrode contact location near ansa lenticularis and lenticular fasciculus results in these enhancements while preserving motor symptom benefits. Visual parameters during visual search tasks with STN DBS on and off will be analyzed. The study's clinical implications are profound, leading to more effective PD treatments, enhancing Veterans’ independence, well-being, delivering high-quality care to US Military Veterans – closely aligned with the mission of the Veterans Health Administration. Furthermore, the multidisciplinary approach contributes valuable insights into DBS applications beyond PD, potentially benefiting a broader population of Veterans.