Characterizing Eye Movements after Pediatric Cortical Resection: Neural Bases and Cognitive Implications - PROJECT SUMMARY Eye movements serve as the front-end of the visual system, sampling visual information to bridge low-level visual input and high-level visuo-cognitive processes. Smooth pursuit for tracking object motion, and saccades for fixating objects are particularly important for these functions. Oculomotor coordination of these movements requires a brain network spanning the cortex and subcortex, to provide input to the oculomotor muscles. While smooth pursuit and saccade circuitry overlaps, they have possibly different developmental trajectories. As such, disrupting these networks at different points in childhood may cause eye movement deficits, whose patterns may elucidate mechanisms of compensation and recovery of the circuits generating intact eye movements. While various brain lesions have resulted in ipsilesional smooth pursuit and contralesional saccade deficits in adults, oculomotor disruption has not been described after pediatric lesions. Up to 11% of pediatric epilepsy patients undergo pediatric epilepsy surgery to treat drug-resistant seizures, and surgery may involve resection of either or both smooth pursuit and saccade network areas. Studying eye movement patterns in these patients is crucial for delineating the recovery and limitations of oculomotor coordination and its role in cognitive processes when the brain is at maximal neuroplastic potential. This study combines behavior and imaging methods to investigate the integrity of smooth pursuit and saccades after pediatric cortical resection, and the postsurgical malleability of these circuits. Aim 1 of this proposal characterizes smooth pursuit and saccade profiles after pediatric hemispherectomy compared to controls. Hemispherectomies result in only one functional hemisphere and are usually performed in childhood. As such, this work will reveal the response of the oculomotor system at the limits of available functional cortex in humans, and while developmental plasticity is possibly at its peak. Aim 2 uses functional MRI to study the neural correlates of smooth pursuit and saccades after focal pediatric cortical resections in two major cortical oculomotor areas – frontal and parietotemporal– compared to controls. This aim will demonstrate how focal disruptions impact eye movement profiles, and whether unaffected neural circuitry adapts to support any intact or compensatory oculomotor function. Finally, Aim 3 examines the neuro-cognitive implications of oculomotor network disruption under more naturalistic conditions in fMRI. Visual search task performance will be correlated with neural activity after pediatric resections involving both oculomotor and attentional areas (frontal, parietal), relative to controls. Overall, this proposal will advance understanding of oculomotor disruption and its neural and cognitive correlates after pediatric epilepsy surgery. This work will inform an understanding of surgical risk, and future interventional investigations. My training plan leverages the expertise of my mentors and resources at Carnegie Mellon and University of Pittsburgh to develop skills in rigorous design and analysis of eye movement and neuroimaging data which I will apply, in future, to pediatric neurology populations.
