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68 Cards in this Set

  • Front
  • Back
What is the pupil?

Where light enters the eye through an opening in the center of the iris.

What focuses the pupil? Are these parts adjustable or not?

The lens (adjustable) and cornea (not adjustable)

What is the retina?

Light is projected onto this structure, and is lined with visual receptors.

In the vertebrate retina, how are messages sent from the eye?

Messages are sent from the receptors at the back of the eye to bipolar cells, who then send their messages to ganglion cells. The ganglion cells' axons join together and travel back to the brain.

What do amacrine cells do?

1) They get info from bipolar cells and send it to other bipolar, amacrine, and ganglion cells.

2) Refine the input to ganglion cells

What do the axons of the ganglion cells form?

The optic nerve

What is the blind spot?

The point at which ganglion cell axons leave (also where blood vessels enter and leave). Has no receptors.

What is the fovea?

A tiny area specialized for acute, detailed vision. Has nearly unimpeded vision due to the blood vessels and ganglion cell axons.

What are midget ganglion cells?

Ganglion cells in the fovea of humans and other primates. Small and responds to just a single cone. Therefore each cone in the fovea has a direct route to the brain.

Why do birds have better eyesight compared to humans?

They have a second fovea, enabling perception of detail in the periphery.

What is a difference between foveal vision and peripheral vision?

Foveal vision has better acuity (sensitivity to detail), whereas peripheral vision has better sensitivity to dim light.

what are rods?

Abundant in the periphery of the human retina, and respond to faint light but are not useful in daylight because bright light bleaches them.

What are cones?

Abundant near the fovea, and are less active in dim light, more useful in bright light, and essential for colour vision.

What is more numerous? Rods or cones?


What provides more of the brain's input? Rods or cones?


What are photopigments?

Chemicals that release energy when struck by light?

What is the range of visible light?

less than 400nm to more than 700nm

What colour is the shortest wavelengths?


What colour is the longest wavelengths?


What is Thomas Young known for?

1) The first to start deciphering the Rosetta stone.

2) Founded the modern wave theory of light

3) Discovered much about the anatomy of the eye

What is the trichromatic theory of colour vision?

We perceive colour through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths. The ratio of these three cones determines a perception of a certain colour.

What happens when the ratio of the three cones is the same and are equally active? What colour do we see?

White or grey

What is the opponent-process theory?

We perceive color in terms of opposites. The brain has a mechanism that perceives color on a continuum. After you stare at one color in one location long enough, you fatigue that response and tend to swing to the opposite.

What is the retinex theory?

The cortex compares info from various parts of the retina to determine brightness and colour for each area.

When a TV is off, its screen appears grey. When you watch a program, parts of the screen appear black, even though more light is actually showing on the screen than when the set was off. What accounts for the black perception?

The black experience arises by contrast with the other brighter areas. The contrast occurs by comparison within the cerebral cortex, as in the retinex theory of color vision.

What is color vision deficiency?


What is color deficiency a result of?

People with certain genes failing to develop one type of cone, or develop an abnormal type of cone. The gene causing this deficiency is on the X chromosome.

What is the general outline of the anatomy of the mammalian visual system?

Rods & cones -> Horizontal cells -> bipolar cells -> amacrine cells & ganglion cells

Where do the optic nerves from the two eyes meet?

The optic chiasm

What is the journey of visual input?

It goes from the thalamus to the visual cortex. Another part also goes to the superior colliculus.

What is the lateral geniculate nucleus (part of the thalamus)?

Sends axons to other parts of the thalamus and the visual cortex. The cortex returns many axons to the thalamus, so the thalamus and cortex constantly feed info back and forth.

what is lateral inhibition?

The retina's way of sharpening contrasts to emphasize the borders of objects. The reduction of activity in one neuron by activity in neighboring neurons.

When light strikes a receptor, does the receptor excite or inhibit the bipolar cells? What effect does it have on the horizontal cells? What effect does the horizontal cell have on bipolar cells?

The receptor excites both the bipolar and the horizontal cell. The horizontal cell inhibits the same bipolar cell that was excited plus additional bipolar cells in the surround.

If light strikes only one receptor, what is the net effect (excitatory or inhibitory) on the nearest bipolar cell that is directly connected to that receptor? What is the effect on bipolar cells to the side? What causes that effect?

It produces more excitation than inhibition for the nearest bipolar cell. For surrounding bipolar cells, it produces only inhibition. The reason is that the receptor excites a horizontal cell, which inhibits all bipolar cells in the area.

What is the receptive field?

An area in visual space that excites or inhibits it.

What is the receptive field of a rod or cone?

The point in space from which light strikes the cell.

What is the receptive field of any neuron in the visual system?

The area of the visual field that excites or inhibits it.

aWhat are parvocellular neurons?

Small cell bodies and small receptive fields. Mostly in or near the fovea.

Detect visual details. Respond to color.

What are magnocellular neurons?

Larger cell bodies and receptive fields. Evenly distributed throughout the retina.

Responds strongly to movement and large overall patterns. Do not respond to color or fine details.

What are koniocellular neurons?

Small cell bodies. Occur throughout the retina.

As we progress from bipolar cells to ganglion cells to later cells in the visual system, are receptive fields ordinarily larger, smaller, or the same size? Why?

They become larger because each cell's receptive field is made by inputs converging at an earlier level.

Where does info from the lateral geniculate nucleus of the thalamus go to?

The primary visual cortex. Area V1.

What happens to people with damage to area V1 in comparison to people with eye damage?

People with damage to area V1 report no conscious vision, no visual imagery, and no visual images in their dreams. People with eye damage lose their vision, but continue to have visual imagery and visual dreams.

What is the phenomenon blindsight?

The ability to respond in limited ways to visual info without perceiving it consciously.

If you were in a darkened room and researchers wanted to "read your mind" just enough to know whether you were having visual fantasies, what could they do?

Researchers could use fMRI, EEG, or other recording methods to see whether activity in your primary visual cortex increased.

What is a simple cell?

A cell in the visual cortex. Has a receptive field with fixed excitatory and inhibitory zones. More excitatory = more response. More inhibitory = less response.

What are complex cells?

Located in areas V1 and V2. Do not respond to the exact location of a stimulus. Responds to a pattern of light in a particular orientation anywhere within its large receptive field. Responds most strongly to a moving stimulus.

What is the best way to classify a cell as simple or complex?

To present the stimulus in several locations. A cell that responds to a stimulus in only one location is a simple cell. One that responds equally throughout a large area is a complex cell.

What are end-stopped or hypercomplex cells?

Resemble complex cells with one exception: It has a strong inhibitory area at one end of its bar-shaped receptive field. Responds to a bar-shaped pattern of light anywhere in its broad receptive field, provided the bar does not extend beyond a certain point.

What do cells within a column of the visual cortex have in common?

Respond best to lines in the same orientation. Similar in preference for one eye or the other, or both equally.

What are feature detectors?

Neurons whose responses indicate the presence of a particular feature.

Eg. Shape, or direction of movement

After processing in areas V1 and V2 of the occipital cortex, where does the info go?

It branches off in several directions into the parietal cortex and temporal cortex.

What is the ventral stream?

The "what" pathway through the temporal cortex. Identifying and recognizing objects.

What is the dorsal stream?

The "how" pathway through the parietal cortex. Importance for visually guided movements.

What do cells in the inferior temporal cortex respond to?

Meaningful objects.

What is visual agnosia?

An inability to recognize objects despite otherwise satisfactory vision.

How does visual agnosia occur?

Usually results from damage to the temporal cortex.

what does the fusiform gyrus of the inferior temporal cortex respond to?

Faces, more than anything else.

What brain areas are responsible for face recognition?

Part of the inferior occipital cortex, the amygdala, and parts of the temporal cortex.

what is prosopagnosia?

Impaired ability to recognize faces.

What is area V4 important for?

Color constancy. The responses of cells in V4 correspond to the apparent or perceived color of an object, which depends on the total context.

What is color constancy?

The ability to recognize something as being the same color despite changes in lighting.

What are the two areas important for motion perception?

MT (Middle temporal cortex /Area V5) and MST (medial superior temporal cortex)

Where do MT and MST receive input from?

The magnocellular path, which detects overall patterns. MT is color insensitive.

What do cells in area MT respond to?

When something moves at a particular speed in a particular direction. Central to the experience of seeing motion.

What do cells in the area MST respond to?

Complex stimuli, such as the expansion, contraction, or rotation of a large visual scene.

What is motion blindness?

The ability to see objects but impairment at seeing whether they are moving or, if so, which direction and how fast.

What is saccades?

When area MT and parts of the parietal cortex decrease activity during voluntary eye movements.