Rescuing Visual Perception in Aging Adults by Restructuring the Alpha-Gamma Neural Code - PROJECT SUMMARY/ABSTRACT In the past century, age-related deficits and dementia have surged, and this trend is expected to intensify with the rapidly aging global population. The decline in visual perception associated with aging significantly impacts health, well-being, and overall quality of life. Key aspects of the visual system, namely contrast sensitivity (the ability to distinguish objects from their backgrounds) and 3D structure-from-motion perception (the capacity to recover depth structure from object motion), undergo pronounced deterioration with age and in age-related diseases, such as Alzheimer's disease (AD). These functions are fundamental to human vision, highly informative of everyday perception, substantially compromised in aging and AD, and predictive of AD-related biomarkers, pathophysiology, and disease severity. Despite advancements in understanding age-related perceptual deficits, neurocomputational insights are lacking, and there are currently no available treatments for impaired perception in older age. Neuroscience theory suggests that the interaction between alpha (8-12 Hz) and gamma (>30 Hz) neural oscillations may indicate a cortical signaling state for optimum visual perception efficiency. This state is achieved when gamma power peaks phase-synchronize to troughs of the alpha cycle, facilitating the integration of feedforward (gamma) and feedback (alpha) information streams. We propose to investigate the neurocomputational mechanisms underlying age-related perceptual impairments across the adult lifespan, focusing on the dynamic phase structure of interacting low- and high-frequency electrophysiological oscillations. Our approach employs functional and structural magnetic resonance imaging (f/MRI) and high-density electroencephalography (EEG), combined with source reconstruction techniques, to investigate the role of alpha-gamma phase amplitude coupling in age-related visual perception deficits. We will construct personalized high-definition transcranial alternating-current stimulation (HD-tACS) protocols in an effort to manipulate alpha-gamma interaction, steer contrast sensitivity and motion perception bidirectionally, and restore these functions in older adults. Encouraging preliminary data suggest the potential to causally manipulate the synchronization between alpha and gamma dynamics, resulting in improved contrast sensitivity and 3D shape perception in older adults. Furthermore, altering the phase preference of alpha-gamma interaction appears to rapidly influence psychophysical mechanisms, causing improvements or impairments in perceptual abilities for younger adults. The overarching goals of this research program are to leverage innovative neuroscience tools and analytic procedures to deepen our understanding of the brain mechanisms behind age-related perceptual impairments. Ultimately, the findings aim to contribute new knowledge to the future development of effective, non-pharmacological interventions for enhancing visual perception in healthy aging and Alzheimer's disease.
