amplitude
36.5 Vision Vision is the only photo responsive sense. Visible light travels in waves and is a very small slice of the electromagnetic radiation spectrum. Light waves differ based on their frequency wavelength = hue and amplitude intensity = brightness . In the vertebrate retina, there are two types of light receptors photoreceptors : cones and rods. Cones, which are the source of color vision, exist in three formsL, M, and Sand they are differentially sensitive to different wavelengths. Cones are located in the retina, along with the dim-light, achromatic receptors rods . Cones are found in the fovea, the central region of the retina, whereas rods are found in the peripheral regions of the retina. Visual signals travel from the eye over the axons of retinal ganglion cells, which make up the optic nerves. Ganglion cells come in several versions. Some ganglion cell axons carry information on form, movement, depth, and brightness, while other axons carry information on color and fine detail. Visual information is sent to the superior colliculi in the midbrain, where coordination of eye movements and integration of auditory information takes place. Visual information is also sent to the suprachiasmatic nucleus SCN of the hypothalamus, which plays a role in the circadian cycle.