Temporal lobe epilepsy is the most common type of epilepsy in adults, is often 
medically refractory, and due to broad actions and long-time scales, current 
systemic treatments have major negative side-effects. However, temporal lobe 
seizures tend to arise from discrete regions before overt clinical behaviour, 
making temporally and spatially specific treatment theoretically possible. Here 
we report the arrest of spontaneous seizures using a real-time, closed-loop, 
response system and in vivo optogenetics in a mouse model of temporal lobe 
epilepsy. Either optogenetic inhibition of excitatory principal cells, or 
activation of a subpopulation of GABAergic cells representing <5% of hippocampal 
neurons, stops seizures rapidly upon light application. These results 
demonstrate that spontaneous temporal lobe seizures can be detected and 
terminated by modulating specific cell populations in a spatially restricted 
manner. A clinical approach built on these principles may overcome many of the 
side-effects of currently available treatment options.