Visual Perception

Pupil

A black disc in the centre of the eye, which is an opening in the iris that helps to control the amount of light entering the eye.

Electrochemical Energy

A form of energy that the brain can process and interpret, also called neural impulses.

Viterous Humour

A jelly-like substance which helps to maintain the shape of the eyeball and also helps to focus light.

Iris

A ring of muscles which expands and contracts to change the size of the pupil and control the amount of light entering the eye.

Lens

A transparent, flexible, convex structure located behind the pupil, which plays an important role in focusing light on to the retina. The lens adjusts the shape of the eye according to the distance in which the object is being viewed.

Aqueous Humour

A watery fluid that helps to maintain the shape of the eyeball and provides nutrients and oxygen to the eye, as well as carrying away waste products.

Ciliary Muscles

Attached to the end of the lens, these muscles expand and contract, enabling the lens to automatically bulge to focus nearby objects onto the retina and flatten to focus distant objects onto the retina.

The Visual Perception System

Consists of the complete network of physiological structures involved in vision.

Organisation

Involves assembling or arranging the features of a visual image in a meaningful way. Visual perception principles are applied at this stage.

Transmission

Involves sending information in the form of electrical impulses along the optic nerve to the brain.

Cornea

Light initially enters the eye through the cornea, a transparent, convex-shaped covering which protects the eye and helps focus light rays onto the retina at the back of the eye.

Electromagnetic Energy

Light.

Retina

Located at the back of the eye and consists of several layers of nerve tissue and photoreceptors (light sensitive visual receptors). The retina receives and absorbs light, and also processes images.

Feature Detector Cells

The ability to detect certain types of stimuli, like movements, shape, and angles, requires specialized cells in the brain called feature detectors

Fovea

The central focal point on the retina in the eye around which the cones cluster. The fovea has only cones around it, which are better for detecting fine detail.

Photoreceptors

The light-sensitive cells in the retina- the rods and cones. Rods are responsible for vision at low light levels. They do not mediate colour vision, and have a low spatial acuity. Cones are active at higher light levels, are capable of color vision and are responsible for high spatial acuity.

Optic Nerve

The optic nerve is behind the eyeball and transmits visual information to the brain.

Visual Cortex

The portion of the cerebral cortex of the brain that receives and processes impulses from the optic nerves.

Selection

The process by which features of the visual stimuli such as size, colour and movement are detected and coded.

Reception

The process by which the eye receives incoming light from the external environment and focuses it onto the retina where an image of the visual stimulus is captured.

Transduction

The process by which the photoreceptors change electromagnetic energy into electrical impulses which can travel along the optic nerve to the brain.

Interpretation

The process of assigning meaning to visual information so that we can understand what we are looking at.

Visual Perception

The process that enables the brain to interpret visual stimuli.

Blind Spot

Visual information travels along the optic nerve in the eye before it begins its journey to the brain for processing. There is a certain spot on the optic nerve that does not have any receptor cells (the area where the optic nerve leaves the eye), and, as a result, can't receive information. The result is the blind spot.