Final answer:
Retinal ganglion cells (RGCs) convey light presence information to the suprachiasmatic nucleus (SCN), helping to regulate circadian rhythms.
Step-by-step explanation:
The retinal ganglion cells (RGCs) carry information about the presence of light to the suprachiasmatic nucleus (SCN) to help regulate sleep-wake cycles. The SCN, located in the hypothalamus, is considered the body's internal clock that controls our circadian rhythms. These specialized RGCs have photosensitive axons that directly project to the SCN from the optic chiasm. They do not process visual images but rather respond to the presence or absence of light, thereby sending information critical for the synchronization of the body's circadian rhythm with the external environment.