When the opsin is activated by photon absorption, the G-protein Transducin starts the signaling cascade that closes the ion channels and hyperpolarizes the receptor. To transmit information on magnetic directions indicated by the amount of Cry1a singlets or triplets, the radical pair mechanism could either independently use the signaling cascade of UV/V opsin, or it could have a separate signaling pathway that affects the state of the ion channels in the outer membrane. 6-Thio-2-Deoxyguanosine Identifying the UV/V cones as magnetoreceptors raises the Rituximab crucial question about the perceptual separation of visual and magnetic information. At the photoreceptor level, the activation of the Cry1a molecule is combined with that of the UV/V opsin to a single output of the UV/V cone. Consequently, mechanisms are needed to separate the two components of the common signal for further processing. Zapka and colleagues recently speculated that if the detection of magnetic directions and daytime vision occurred in the same type of photoreceptors, high light-induced activation might override or mask the magnetic compass, and considered the possibility of a second receptor mechanism for magnetoreception during the day. However, when birds use their magnetic compass under ��white�� light of high intensity with all four cone types activated, the primary processes of magnetoreception are the same radical-pair processes as at night, as indicated by the disrupting effect of radio-frequency fields. Several mechanisms are conceivable for separating magnetically induced and visual output, which could be performed directly at the retinal level or more centrally. A comparison of the output of adjacent UV/V cones with and without cryptochrome can be ruled out, because the present study shows that every UV/V cone contains Cry1a. Yet other comparisons, e.g. with the blue cones, seem possible, as there is some overlap in the excitation range of these two cones. Too strong asymmetry of activation by the visual stimulus, e.g. if one of the receptors were strongly activated and the other hardly at all, would hamper this comparison.