Restructuring the Alpha-Gamma Code in Aging Vision

Tests whether age-related visual deficits arise from disrupted alpha-gamma coupling in visual cortex (V1) and MT. Uses fMRI, source-resolved HD-EEG, and personalized complex-waveform HD-tACS to (1) quantify aging effects on phase-amplitude coupling, (2) drive PAC into a preferred "gamma-at-alpha-troughs" state, and (3) bidirectionally change perception by aligning gamma to alpha troughs vs peaks. Two five-day, double-blind, sham-controlled studies (n=120 each) target contrast sensitivity (V1) and 3D shape-from-motion (MT), aiming for mechanistic insight and remediation in older adults with implications for ADRD.

Inclusion Criteria: * 18+ years of age or older * normal or corrected-to-normal visual acuity, color vision, and stereo vision Exclusion Criteria: * not pregnant, * no metal implants in head, * no implanted electronic devices, * no history of neurological problems or head injury, * no skin sensitivity, * no claustrophobia, * no dementia (normal Mini Mental State Examination between 24-30; Montreal Cognitive Assessment \> 25) * no depression (normal Beck Depression Inventory II \24; MoCA\>25) * cannot be taking any psychoactive medication.