Electrolytic lesions to the optic chiasm affect circadian locomotor rhythms in lizards

Electrolytic lesions to 85-95% of both optic nerves at the level of the optic chiasm (OC-X) induce a significant shortening of the freerunning period (tau) of locomotor rhythms in Podarcis sicula held in constant temperature (29°C) and constant darkness. Together with previous data in P.sicula, showing that also retinalectomy (RET-X) in constant darkness mostly induces a shortening of tau, the present results demonstrate that the retinae play a central role in the control of behavioural circadian rhythmicity independently of light perception. The fact that OC-X and RET-X affect locomotor rhythms in the same way (mostly by shortening tau) strongly supports the contention that the influence of the retinae on the circadian system is neurally mediated.