Chronic 40 Hz light flicker mitigates epileptogenesis through a visual pathway associated with the dorsal lateral geniculate nucleus shell

Altered gamma activity is associated with epilepsy. Gamma entrainment using sensory stimuli (GENUS), a non-invasive, exogenous stimulation by rhythmic 40 Hz light flicker, strengthens gamma activity in the primary visual cortex (V1) and suppresses spike generation. Here, we assessed the effect of GENUS on epileptogenesis in male mice with status epilepticus induced by pilocarpine. We found that GENUS immediately increased gamma activity and reduced epileptiform spikes in epileptic mice. After six weeks of GENUS treatment in epileptic mice, significant reductions were observed in neuronal loss and gliosis, brain hyperexcitability was ameliorated, and epilepsy-related behavioral performance was improved. We determined that the increased 40 Hz oscillations and reduced seizure susceptibility induced by GENUS were dependent on the visual circuit associated with ON-OFF direction-selective retinal ganglion cells, glutamatergic neurons in the shell of the dorsal lateral geniculate nucleus, and parvalbumin-expressing fast-spiking interneurons in the superficial 2/3 layer of V1.