Psychology - Chapter 4 The Visual System Part 2

central part of the retina and is responsible for acuity, or sharpness of vision.

Rods: - long and narrow

- enables us to see basic shapes and form

- we rely on rods to see in low levels of light

- there are no rods in the fovea

Cones:

- shaped like small cones

- gives us colour vision

- require more light, used when reading

our eyes adjustment to when we enter a dimly lit room, from a bright environment.

Chemical that change following exposure to light.

contains the axons of ganglion cells, travels from the retina to the rest of the brain.

The place where the optic nerve connects to the retina. It is a region of the retina containing no rods and totally devoid of sense receptors.

The optic nerve travels from the retina to the rest of the brain. After toptic nerves leave both eyes, they come to a fork in the road called the optic chaism.

Half of the axons cross in the optic chiasm and the other half stay on the same side.

Within a short distance, the optic nerves enter the brain, turning into optic tracts.

The optic tracts send most of their axons to the visual part of the thalamus and then to the primary visual cortex.

The remaining axons go to structures in the midbrain, particularly the superior colliculus.

Ability to use minimal patterns to identify objects.

Simple and complex cells. They detect lines and edges.

To higher visual areas like V2, along two major routes, one of which travels to the upper parts of the parietal lobe and the other of which travels to the lower part of the temporal lobe.

Rules governing how we perceive objects as wholes within their overall context.

Proximity: objects physically close to each other tend to be perceived as unified wholes.

Similarity: All things being equal, we see objects as compromising a whole much more so than dissimilar objects.

Continuity: We still perceive objects as wholes, even if other objects block part of them.

Closure: when partial visual information is present, our brains fill in what's missing. (contours)

Symmetry: we perceive objects that are symmetrically arranged as wholes more often than those that aren't.

Figure-Ground: perceptually, we make an instantaneous decision to focus attention on what we believe to be the central figure, and largely ignore what we believe to be the background.

one we can perceive in two ways.

We don't need an exact picture of a face to recognize it.

| The lower part of the temporal lobe responds to faces.

V5, region located along the pathway that leads to the parietal lobe. Neurons in this region will respond to both the direction and the speed of motion.

Illusory perception of movement produced by the successive flashing of images.

Proposes that we base our colour vision on three primary colours. Based on us having three different cones.

Most often due to genetic mutations or brain damage leading to the inability to see all colours.

have only one type of cone.

Most colour blind people. Have two types of cones.

Holds that we perceive colours in terms of three pairs of opponent cells. Red or green, blue or yellow, black or white. Our nervous system uses both trichromatic and opponent processing principles during colour vision but, different neurons rely on one principle more than the other.

Occur when we've stared at one colour for a long time, look away, and often see replica of the same image. Arise from visual cortex's processing of information from our rods and cones.

Ability to see spatial relations in three dimensions.

Monocular depth cues and binocular depth cues. Mono is one eye, bino is both eyes.

relative size: more distant objects look smaller

texture gradient: texture less apparent with greater distance.

interposition: the close object blocks our view of the further one.

linear perspective: the outlines of rooms or buildings converge as distance increases.

height in plane: distant objects seem to appear higher.

light and shadow: objects cast shadows that give us a sense of their 3D form.

give us a sense of what's located where in stationary scenes.

Ability to judge the distance of moving objects from their speed.

Nearby objects seem to move faster than those far away travelling at the same speed. Also works when we are moving.

Our left and right eyes transmit different information for near objects but see distant objects similarly.

When we look at nearby objects, we focus on the relexively by using our eye muscles to turn our eyes inward.

Dramatic reduction in the ability to see.

Patients can't seamlessly string still images processed by their brains into the perception of ongoing motion.

Deficit in perceiving objects. A person with this condition can tell us the shape of an object but can't recognize or name it.

Remarkable phenomenon in which blind people who've experienced damage to a specific area of their cortex can still make correct guesses about the visual appearance of things around them. Coarser visual information still reaches the visual information cortex through an alternative pathway and bypasses V1.