Module 19: Vision: Sensory and Perception Processing

Transduce

Transform

How do we see?

Light travels in waves, and the shape of those waves influences what we see

Wavelength

The distance from the peak of one light or sound wave to the next

Hue

The color that is determined by the wavelength of light that we see

Intensity

The amount of energy in a light or sound wave, which influences what those with typical vision or hearing perceive as brightness or loudness

Intensity is determined by the wave’s…

amplitude (height)

Cornea

Where light enters the eye from

Purpose of the Cornea

Bends light to help provide focus

Pupil

Small adjustable opening that light passes through after it passes the cornea

Iris

Surrounds the pupil and controls its size, colored muscle that dilates or constricts in response to light intensity, also responds to cognitive and emotional states

Lens

The transparent part of the eye that the light hits after passing through the pupil, then focuses the light rays into an image on our retina

Retina

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

Accomodation

A process where the eye's lens changes shape to focus near or far objects on the retina

Myopia

Nearsightedness, seeing near objects clearly but not distant objects

How do we understand the world?

The retina does not ‘see’ a whole image. Its millions of receptor cells convert the particles of light energy into neural impulses to forward those to the brain, which reassembles them, right side up, into what we perceive

Rods

Retinal receptors that detect black, white, and gray, and are sensitive to movement

What are rods responsible for when cones don’t respond?

Peripheral and twilight vision

Cones

Retinal receptors that are concentrated near the center of the retina and function in well-lit conditions, detect fine detail and give rise to color sensations

Bipolar Cells

Retinal neurons that carry signals from photoreceptors (rods + cones) to ganglion cells

Ganglion cells

Neurons that are essential for vision, activated by bipolar cells

Optic nerve

The nerve that carries neural impulses from the eye to the brain

How is an optic nerve formed?

Made up of ganglion cells whose axons twine together like rope

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/main point in the retina where the eye’s cones cluster

How are messages transmitted from the eye to the brain?

One cone transmits a message to one bipolar cell, which relays the message to the visual cortex

Why are connections so direct (ONE cone connects to ONE bipolar cell)?

These direct connections preserve the cone’s precise info, making them better able to detect more detail

Color processing

When we see a specific color, that color is being reflected, while all other colors are being absorbed

Young-Helmholtz Trichromatic (three-color theory)

The theory that the retina contains three different types of color receptors: one most sensitive to red, one to green, and one to blue (when stimulated in combination, can produce the perception of any color)

Color-Deficient Vision

Cones don’t work properly, causing difficulty seeing or distinguishing certain colors 

Opponent-Process Theory

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

Some cells are inhibited by red and stimulated by green, meaning we can’t see colors that are reddish-green. This is an example of the…

Opponent-process theory

Feature Detectors

Nerve cells in the brain’s visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement

Supercell Clusters

Groups of cells that respond to more complex patterns of information

Fusiform Face Area

A region in the temporal lobe that responds to faces and is crucial for face perception and recognition

Parallel Processing

Processing multiple aspects of a stimulus or problem simultaneously

Gestalt

An organized whole/our tendency to put together pieces of information to form a meaningful whole

Figure-ground

The organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Grouping

The perceptual tendency to organize stimuli into logical groups

Depth-Perception

The ability to see objects in three dimensions, although the images that strike the retina are two-dimensional

We are able to judge distance because of…

Depth perception

Visual Cliff

A laboratory device for testing depth perception in infants and young animals

Binocular Cues

A depth cue, such as retinal disparity that depends on the use of two eyes

Retinal Disparity

A binocular cue for perceiving depth: comparing retinal images from the two eyes, the brain computes distance

The greater the disparity (difference) between the two images, the… the object

closer

Monocular Cues

A depth cue available to either eye alone

Interposition

A monocular cue where one object that is partially blocking another is perceived as being closer

Linear Perpective

A monocular cue that tricks the brain in perceiving depth and distance in flat (2D) images

Motion Perception

Shrinking objects are retreating and enlarging objects are approaching

Phi Phenomenon

An illusion or movement created when two or more adjacent lights blink on and off in quick succession

Perceptual Constancy

Perceiving objects as unchanging (having consistent color, brightness, shape, and size), even as illumination and retinal images change

Relative Luminance

The amount of light an object reflects relative to its surroundings

Shape Constancy

Those with typical vision perceive the form of familiar objects as constant even while the retinas receive changing images of them

Size Constancy

Those with typical vision perceive an object as having an unchanging size, even while distance from it varies

For sensory and perceptual development, there is a… where exposure to certain stimuli or experiences is required

critical period

Perceptual Adaptation

The ability to adjust to changes sensory input, including an artificially displaced or inverted visual field

Proximity

Gestalt principle where we group nearby objects together as a unit, seeing relatedness in closeness

Similarity

Gestalt principle where we group things that look alike (color, shape size)

Closure

Gestalt principle where we mentally fill in gaps or incomplete information

Texture Gradient

A monocular depth cue where surfaces close to us appear detailed, and when they are farther the texture seems smoother

Relative Motion

A monocular depth cue where closer objects seem faster and farther objects seem to be slower or not moving

Light and Shadow

A monocular cue where shading suggests depth and dimension

Relative Size

A monocular cue where when two objects are similar, the one casting a smaller image on our retina is perceived as farther away

Lightness Constancy

The ability to see an object with the same brightness even when the lighting around you is different

Sclera

The outer layer of the eye that is white and smoothly transitions to the cornea

Astigmatism

A disorder of the curvature of the cornea or lens that results in difficulty seeing fine detail

Conjunctiva

The thin layer of mucous membrane that covers the outer eye and inside the eyelids for protection

Aqueous Humor

Clear fluid located near the front of the eye that supplies nutrients to the eye, removes waste, and maintains the shape of the eye

Cataract

A condition where the lens of the eye is cloudy. Can affect vision due to aging, injury, or disease

Vitreous Humor

Clear gelatinous fluid that fills the area behind the lens to the back of the eye

Choroid

A bunch of blood vessels that keep the eye healthy by providing oxygen and nutrients

Height in Plane

A monocular depth cue where objects higher up in our visual field are perceived as farther away, and vise versa

Monochromatism

A type of color blindness where the person sees everything in the shade of one color

Convergence

A binocular cue for depth perception where your eyes turn inward (converge) to focus on nearby objects