1. VISION
Module 18

2. Vision We do not see color, we see electromagnetic energy
Two physical characteristics of light:
Wavelength – the distance from the peak of one light or sound wave to the next.
Determines Hue – the dimension of color
Intensity – the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave’s amplitude.

3. The Eye Cornea – transparent protector
Pupil – adjustable opening in the center of the eye through which light enters
Iris – a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
Lens – the transparent structure behind the pupil that changes shape to focus images on the retina.
Accommodation – process of lens changing shape to focus near or far objects on the retina

4. The Retina
Retina – light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information
Receives an upside-down version of the image and does not read the image as a whole
Its receptor cells convert light energy into neural impulses(transduction) that are sent to the brain and constructed into a perceived, upright image.
Receptor cells: rods and cones
Rods – retinal receptors that detect black, white, and grey; necessary for peripheral and twilight vision, when cones can’t respond.
Cones – receptor cells that are concentrated near the center of the retina and that function in daylight or well-lit conditions. They detect fine detail and give rise to color sensations

5. The Retina
Optic nerve – nerve that carries neural impulses from the eye to the brain
Messages are sent through bipolar cells and ganglion fibers
Blind spot – the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.
Fovea – the central focal point in the retina, around which the eye’s cones cluster

7. Visual Information processing
Receptor cells  bipolar cells  ganglion cells  optic nerve  thalamus  visual cortex in occipital lobe
Feature detectors – nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement
Parallel processing – the processing of several aspects of a problem simultaneously; the brain’s natural mode of information processing for many functions
Visual disabilities occur when there is a disruption of these neural networks
Ex- inability to see movement and Blindsight – ability to respond to something not consciously perceived

8. Color Vision
Color – the rejection of the wavelength, our mental construction of the object not actually the object
Low threshold for color – can see 1million color variations
1 in 50 color deficient, usually male - genetically sex-linked
games?pb_page=2&game=timbennett 10/can-you-pass-the-color-blind-test

9. Color Vision 2 color theories:
Young-Helmholtz trichromatic theory – the theory that the retina contains 3 different color receptors – one most sensitive to red, one to green, and one to blue – which when stimulated in combination can produce the perception of any color
Doesn’t explain colorblindness
Opponent-process theory – the theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green
Color processing occurs in two stages: The retina’s red, green, and blue cones respond in varying degrees to different color stimuli (trichromatic theory). Their signals are then processed by the nervous system’s opponent-process cells (opponent-process theory)