Visual Perception and Distortions

The visual sensory system consists of a complete network of physiological structures involved in vision

Stimulus: light is reflected, or given out by, a visual image and enters the eye.

Let's take a closer look at the eye.

CORNEA: Transparent, convex-shaped (curved outwards) covering which protects the eye and helps to focus light rays onto the retina at the back of the eye

AQUEOUS HUMOR: A watery fluid which helps to maintain the shape of the eyeball and provides nutrients and oxygen to the eye, as well as carrying away waste products

PUPIL: An opening in the iris that helps to control the amount of light entering the eye.

IRIS: The coloured part of the eye consisting of a ring of muscles that expand or contract to change the size of the pupil and control the amount of light entering the eye

šLENS: A transparent, flexible, convex structure located immediately behind the pupil which plays a major role in focusing light onto the retina

šRETINA: Layer of neural tissue at the back of the eye that receives and absorbs light, and processes images for transmission to the brain (reception and transduction occurs here)

šPHOTORECEPTORS: A light-sensitive visual receptor cell in the eye; see rods and cones

šRODS: Photoreceptor in the eye’s retina that responds to very low levels of light; primarily responsible for night vision

šCONES: Photoreceptor in the retina of the eye that responds to high levels of light and is primarily responsible for vision in light / bright conditions , colour vision and detecting fine details.

šOPTIC NERVE: Carries visual information from the retina to the primary visual cortex.

šBLIND SPOT: A small area on the retina at the back of the eye where there are no photoreceptors so light cannot be detected.

šOPTIC CHIASM: Point where the axons of ganglion cells in the optic nerve cross.

Electromagnetic energy in the form of light enters the eye

Photoreceptors rods & cones detect and respond (reception) AND change (transduce) the electromagnetic energy (light) into the electrochemical energy (a nerve impulse)

The electromagnetic energy has now been changed into electrochemical energy

Neural messages are sent or transmitted via the optic nerve (from the photoreceptors to the thalamus and then visual cortext in the occipital lobe

Transmission can not occur without transduction

Neural message are also called action potentials

When neural messages (or action potentials) are received by the primary visual cortex (in the occipital lobe), interpretation occurs.

Other lobes in the brain will also play a role. For example interpretation (or perception) will occur by drawing on memories.