The<unk>  (from "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the<unk> , which translates that image into electrical neural impulses to the brain to create visual perception. The<unk>  serves a function analogous to that of the film or image sensor in a camera. The neural<unk>  consists of several layers of neurons interconnected by synapses and is supported by an outer layer of pigmented epithelial cells. The primary light-sensing cells in the<unk>  are the photoreceptor cells, which are of two types: rods and cones. Rods function mainly in dim light and provide black-and-white vision. Cones function in well-lit conditions and are responsible for the perception of colour, as well as high-acuity vision used for tasks such as reading. A third type of light-sensing cell, the photosensitive ganglion cell, is important for entrainment of circadian rhythms and reflexive responses such as the pupillary light reflex. Light striking the<unk>  initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses that are sent to various visual centres of the brain through the fibres of the optic nerve. Neural signals from the rods and cones undergo processing by other neurons, whose output takes the form of action potentials in<unk> l ganglion cells whose axons form the optic nerve. Several important features of visual perception can be traced to the<unk> l encoding and processing of light. In vertebrate embryonic development, the<unk>  and the optic nerve originate as outgrowths of the developing brain, specifically the embryonic diencephalon; thus, the<unk>  is considered part of the central nervous system (CNS) and is actually brain tissue. It is the only part of the CNS that can be visualized non-invasively.
Retina
Forebrain
Hindbrain
Barrel cortex
Brainstem
Auditory cortex
Electuary
Diencephalon