A century ago, Hans Berger recorded the first brain activity with electroencephalography, a method that remains invaluable in research and clinical settings to further understand mechanisms involving the cerebral cortices. Different oscillation frequencies, indicative of various mental states such as sleep, rest, wakefulness, concentration and perception, are detectable through electroencephalography. The typical canonical oscillations alter with increasing age or in certain diseases. Emerging research explores how entraining brain oscillations could be a therapeutic target, using sensory stimuli, such as light and sound, to modulate these. This chapter explores the mechanisms and role of astrocytes underlying brain oscillations and their alterations in diseases, with a focus on gamma oscillations in Alzheimer’s disease and major depressive disorder and introduces non-invasive, light-based gamma stimulation as a potential novel treatment approach in two clinical studies, ALZLIGHT (Trial ID: NCT05260177) and FELIX (Trial ID: NCT05680220).