It begins with the eye

Figure 4.
(Illustration taken from Freberg, 2006. Discovering Biological Psychology.)


Figure 4 above shows light entering the eye through the cornea and lenses and projected on to the retina, at the back of the eye. 5 types of neurons; the rods and cones, bipolar cells, ganglion cells, amacrine cells and horizontal cells form the retinal layers. The receptors made up of rods and cons, bipolar cells and ganglion cells transmit the signals vertically through the retina, whilst the horizontal and amacrine cells transmit signals horizontally across the retina.

Light is changed to energy in the receptive fields as electrical signals and sent to the visual cortex neurons of the brain via the LGN (lateral geniculate nucleus) through the firing of the ganglion cells when light passes through the receptive field. The ganglion cells respond to the antagonistic receptive photoreceptors. The receptive field consists of on-centre, off-surround ganglion cells and off-centre, on-centre ganglion cells as in figure 5.