Contribution of classic photoreceptors to entrainment.

The ability to phase shift and entrain in response to light is spared in retinally degenerate mice (rd/rd). In the present work, fewer retinally degenerate C57BL/6 mice than wildtypes entrained in dim lights, suggesting that rods and/or cones contribute toward entrainment even though they are not necessary. Thresholds for entrainment appear to be a more sensitive test of deficits in entrainment than phase shifts in response to light pulses.