Retina. Computer model of part of a healthy human retina, the light-sensitive tissue that lines the inside of the eye. Light strikes specialized nerve cells (neurons, far right) that convert light energy into nerve impulses. The highly-sensitive rods (blue) respond to dim light, while cones (purple) detect red, blue and green light. Each nerve impulse passes along the nerve fibre from the neuron's cell body (round), passing across the synapses (tiny gaps) to other neurons (green & red). Finally, signals pass into the optic nerve (brown, top left) and on to the brain. This model was created at the Laboratory of Neuro Imaging (LONI) at UCLA, USA.