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Retinal Input

Meaning

Retinal Input refers to the light-based sensory information received by the photoreceptor cells and, critically, the intrinsically photosensitive Retinal Ganglion Cells (ipRGCs) in the eye, which transmit signals not for image formation but for regulating non-visual biological processes. This input is the primary zeitgeber, or time-setter, for the human circadian system, directly influencing the central biological clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. It is the master environmental signal for neuroendocrine timing and synchronization.