Temporal Light Modulation Activation in Visual Cortex – A 7T fMRI Study on Healthy Subjects

This study investigates the effects of high-frequency temporal light modulation (TLM) on neural activity using functional magnetic resonance imaging (fMRI) in healthy individuals (age 18–50 years). We examined stimulation frequencies both below (50 Hz) and above (≥100 Hz) the perceptible threshold for visual flicker. Our findings revealed that 50 Hz TLM, which is perceived as flickering, leads to substantial activation in visual regions, particularly the lateral occipital cortex. Notably, 100 Hz TLM, which is not perceived as flickering, also elicited similar but weaker activation patterns, indicating that high-frequency TLM can affect neural responses even without conscious perception. Additionally, we observed deactivation in several brain regions during TLM stimulation, suggesting a shift in attentional focus to external stimuli. These results underscore the potential for high-frequency TLM to influence brain activity, with implications for cognitive performance and health. Overall, this study highlights the importance of considering both visual and nonvisual effects of TLM on neural activity, particularly for individuals sensitive to visual stress.