Biological Psychology - Chapter 6: Vision

Front 1

What is a "receptor potential?"

Back 1

Receptor potential: Local depolarization or hyperpolarization of a neuron membrane. Stimulus receptors produce receptor potentials when activated by a stimulus.

Front 2

What is the "law of specific nerve energies?"

Back 2

The "law of specific nerce energies": Any activity by a particular nerve always conveys a characteristic kind of information.

Front 3

Who formulated the "law of specific nerve energies?"

Back 3

Johannes Muller, 1838

Front 4

Describe the results of the experiment in which one optic nerve of an immature ferret was attached to the auditory cortex.

Back 4

The auditory cortex connected to the optic nerve showed some characterisitcs of a visual cortex, but not all; the auditory cortex received and processed VISUAL information.

Front 5

What are the three steps in processing visual stimuli?

Back 5

The three steps in processing visual stimuli:
1. Reception
2. Transduction / Coding
3. Conscious awareness

Front 6

What is a single visual stimulus called?

Back 6

A mite

Front 7

Define "pupil."

Back 7

Pupil: An opening in the center of the iris in which light enters the eye.

Front 8

Define "macula."

Back 8

Macula: The portion of the retina with the greatest ability to resolve detail.

Front 9

Define "retina."

Back 9

Retina: Rear surface of the eye which is lined with visual receptors.

Front 10

Define "fovea."

Back 10

Fovea: Central portion of the macula specialized for acute, detailed vision in humans. The blood vessels and ganglion cells are almost absent. Little convergence between the receptors and their postsynaptic cells, known as "bipolar cells."

Front 11

What is the route within the retina?

Back 11

Within retina, light >>> photoreceptors >>> bipolar cells >>> ganglion cells >>> optic nerve >>> brain.

Front 12

What is the "blind spot?"

Back 12

The "blind spot" is the point at which the optic nerve leaves the eye, because no visual receptors.

Front 13

Compare foveal and peripheral vision with regard to acuity.

Back 13

The fovea is better at discerning detail because only a few receptors funnel their input into each postsynaptic cell; in peripheral vision many receptors send their input to each bipolar cell.

Front 14

What is "peripheral vision?"

Back 14

Peripheral vision: caontains a greater number of receptors for each bipolar cell; proportion of roads increases towards the periphery - the extreme periphery has only rods.

Front 15

Compare foveal and peripheral vision with regard to sensitivity to dim light.

Back 15

Foveal vision: Useful for distinguishing among bright lights; responds poorly to dim lights.
Peripheral vision: responds well to faint lights; responds poorly to bright lights.

Front 16

Compare foveal and peripheral vision with regard to color vision.

Back 16

Color Vision:
- Foveal vision: Good (many cones)
- Peripheral vision: Bad (few cones)

Front 17

What is the specific role of light in the initiation of a response in a receptor?

Back 17

Light activates photopigments within receptors >>> which cause the receptors to create receptor potentials, etc.

Front 18

What is a "photopigment?"

Back 18

Photopigments: Chemicals that release energy when struk by light. Both rods and cones contain different kinds of photopigments.

Front 19

What is the relationship of "11-cis-retinal" to "all-trans-retinal?"

Back 19

Light converts 11-cis-retinal (a derivative of vitamin A) into all-trans-retinal - thus releasing energy that activates second messengers with the cell.

Front 20

What is an "opsin?"

Back 20

Opsins: The proteins bound to the photopigments 11-cis-retinal. Opsins modify its photopigment's sensitivity to different wavelengths of light.

Front 21

What kind of electrical respnse is produced in the receptors, and how does this affect the bipolar cells with which it synapses?

Back 21

Receptors have inhibitory synapses onto the bipolar cells. Thus, hyperpolarization of receptor cells leads to excitation of bipolar cells; depolarization of receptor cells leads to inhibition of bipolar cells.

Front 22

What is the range of visible light?

Back 22

Range of visible light: between roughly 400nm to 700nm.

Front 23

What is the "trichromatic theory?"

Back 23

Trichromatic theory: There are three different kinds of cones, each sensitive to a differenet set of wavelengths. Based on psychophysical observations.

Front 24

Who developed the "trichromatic theory?"

Back 24

The "trichromatic theory" was first developed by Thomas Young, and later modified by Hermann von Helmholtz.

Front 25

What is the "opponent-process theory?"

Back 25

Opponent-process theory: Color is perceived in terms of paired opposites: white-black / red-green / yellow-blue.

Front 26

What are "negative afterimages?"

Back 26

Negative afterimages: The result from fatiguing a response by opponent-process cells.

Front 27

Why does the presence of cones in the retina of a given species not guarantee color vision?

Back 27

Their brains may not be able to interpret the signals it receives as different colors.

Front 28

What is the "retinex theory?"

Back 28

Retinex theory: Accounts for color constancy. When information from various parts of the retina reaches the cortex, the cortex compares each of the inputs to determine the brightness and color perception of each area.

Front 29

What is the genetic basis for the most common form of color vision deficiency?

Back 29

Color vision deficiency (color blindness): Red-green color blindness most common form. More common in males because the genes are on X chromosomes.

Front 30

What is "color constancy?"

Back 30

Color constancy: The ability to recognize the color of objects despite changes in lighting. This ability is not explained by the trichromatic or opponent-process theories; is explained by the retinex theory.

Front 31

What does "lateral" mean?

Back 31

Lateral: Of or on the side.

Front 32

What does "temporal" mean?

Back 32

Temporal: Of or near the temple or temples of the head.

Front 33

What is the name of the site where the right and left optic nerves meet?

Back 33

The "optic chiasm."

Front 34

What percentage of axons cross to the opposite side of the brain in humans? In species with eyes far to the sides of their heads?

Back 34

Half of the axons from each eye cross to the opposite side of the brain, and half stay their original side.

Front 35

Where do most axons in the optic nerve synapse? Where do some other optic nerves synapse?

Back 35

Most axons in the opic nerve synapse in the lateral geniculate nucleus (LGN) of the thalamus.

Front 36

What is the destination of axons from the "lateral geniculate nucleus (LGN)?"

Back 36

The visual cortex.

Front 37

What is the order of connections from the retina towards the visual cortex?

Back 37

Rods and cones make synaptic connections with horizontal cells and bipolar cells.
The horisontal cells make inhibitory contact onto bipolar cells which in turn make synapses with amacrine cells and ganglion cells.
Axons of the ganglion cells >>> optic nerve >>> optic chiasm >>> lateral geniculate nucleus (LGN) of the thalamus >>> visual cortex.

Front 38

What is a neuron's "receptive field?"

Back 38

Receptive field: The portion of the visual field to which any neuron responds is that neuron's receptive field.

Front 39

What is "lateral inhibition?"

Back 39

Lateral inhibition: Reduction of activity in one neuron caused by activity in a neighboring neuron in the cerebral cortex. Used to heighten contrast at borders.