Module 18: Vision

Rods

Rods

________: retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones dont respond.

Lens

________: transparent structure behind the pupil that changes shape to help focus images on the retina.

Iris

________: ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening.

Accommodation

________: process by which the eyes lens changes shape to focus near or far objects on the retina.

Young Helmholtz

________ trichromatic (three- color) theory: theory that the retina contains 3 different color receptors- one most sensitive to red, one to green, on to blue- which, when stimulated in combination, can produce the perception of any color.

single bipolar cells

Each cone transmits to a(n) ________ that helps relay the cones individual messages to the visual cortex, which devotes and large area to input the fovea.

Intensity

________: the amount of energy in light or sound waves, which we perceive as brightness or loudness, determined by the waves amplitude (height)

visual scene

To analyze a(n) ________, the brain divides it into subdimensions- motion, form, depth, color- and works on each aspect simultaneously.

Cones

________: retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well- lit conditions.

Supercell clusters

________ in other critical brain areas respond to more complex patterns.

Davide Hubel

________ and Torsten Wiesel received a nobel prize for their work on feature detectors.

Hue

________: dimension of color that is determined by the wavelength of light.

central focus

Fovea: ________ point in the retina, around which the eyes cones cluster (figure 18.3)

Pupil

________: adjustable opening in the center of the eye through which light enters.

optic nerve

Blind spot: point at which the ________ leaves the eye, creating a "blind "spot because no receptor cells are located there (figure 18.5)

visual cortex

In the ________, feature detectors respond to specific features of the visual stimulus.

Visible light

________ is a very small section of the electromagnetic spectrum (figure 18.1)

Wavelength

________ determines the lights hue.

pupil

(3) Surrounding the ________ is the iris, a colored muscle that dilates or constricts in response to light intensity or inner emotions.

18-1

What is the energy that we see as visible light, and how does the eye transform light energy into neural messages

The Stimulus Input

Light Energy

Wavelength

distance from the peak of one wave to the next peak

Hue

dimension of color that is determined by the wavelength of light

Ex

the colors we know, blue, green, etc,

Intensity

the amount of energy in light or sound waves, which we perceive as brightness or loudness, determined by the waves amplitude (height)

Pupil

adjustable opening in the center of the eye through which light enters

Iris

ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

Lens

transparent structure behind the pupil that changes shape to help focus images on the retina

Retina

light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

Accommodation

process by which the eyes lens changes shape to focus near or far objects on the retina

Rods

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones dont respond

Cones

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions

Optic nerve

nerve that carries neural impulses from the eye to the brain

Blind spot

point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there (figure 18.5)

Fovea

central focus point in the retina, around which the eyes cones cluster (figure 18.3)

Cones

detail and color

Rods

Faint light

18-2

How do the eye and the brain process visual information

Ex

Turn your eyes to the left, close them, and then gently rub the right side of your eyelid with your fingertip

Feature detectors

nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement

Parallel processing

processing of many aspects of a problem simultaneously; the brains natural mode of information processing for many functions, including vision

Young-Helmholtz trichromatic (three-color) theory

theory that the retina contains 3 different color receptors-one most sensitive to red, one to green, on to blue-which, when stimulated in combination, can produce the perception of any color

Ex

there are no receptors sensitive to yellow, we see yellow when mixing red and green light, which stipulates both red and green sensitive cones

Opponent-process theory

theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision

Ex

some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green