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Aims: Electrical and pharmacological stimulation of the superior colliculus (SC) has been described to mediate a variety of behaviours ranging from freezing, escape and orientation. Here, we investigated the effect of prolonged optogenetic stimulation of the SC. Methods: We used the stable step-function opsin (SSFO), a modified ChR2 channel, which stays active for 20-30 minutes. The right SC of C57Bl6J mice was stereotactically injected with an AAV2/7-CaMKII-SSFO vector. Stimulation consisted of a 2s blue light pulse of 50 mW/mm2on day 1, 3 and 5 and a different batch of animals was stimulated with light powers ranging from 0,05 mW/mm2 to 50 mW/mm2. Results: Upon stimulation with the highest light power, all mice displayed strong escape behaviour at first, running around in their cage. After about 30 seconds they quieted down and showed a counter-clockwise turning behaviour for up to 30 minutes. Using lower light power, there was no escape response , leaving only the long-lasting contralateral orientation turning. Conclusions: At high light powers, SSFO-mediated SC stimulation resulted in a short escape response, despite the prolonged nature of the stimulation that is indicated by the long-lasting turning behaviour. These findings suggest that the circuit for escape behaviour might respond mainly to stimulus onset and loses its responsiveness upon prolonged stimulation. Furthermore, as lower light powers only elicited turning behaviour, stimulus size appears to be an important factor in triggering escape but not orientation. In summary, our data indicate differential response properties of the collicular circuits mediating escape and orientation.