Vision and Visual System Lecture Notes

A comprehensive set of question-and-answer flashcards covering major concepts, structures, theories, and disorders related to the visual system as outlined in the lecture notes.

What is the function of specialized receptors in our senses?

They respond to specific energy types and convert them into electrochemical patterns for the brain.

What is the law of specific nerve energies?

Activity by a particular nerve always conveys the same kind of information to the brain.

Give an example of the law of specific nerve energies.

Impulses in one neuron indicate light; impulses in another indicate sound.

What is light?

Electromagnetic radiation within the visible spectrum.

How does light enter the eye?

Through the pupil and is focused by the lens and cornea onto the retina.

What is the retina?

The rear surface of the eye, lined with visual receptors.

What is the pupil?

The opening in the center of the iris where light enters the eye.

What is the cornea?

The transparent front part of the eye that helps focus light onto the retina.

What is the lens?

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

What are visual receptors?

Specialized neurons (rods and cones) located in the retina.

What is the fovea?

The central portion of the retina with the highest visual acuity.

What are rods?

Retinal receptors that detect black, white, and gray; necessary for peripheral and night vision.

What are cones?

Retinal receptors concentrated near the fovea that detect fine detail and color.

How many types of cones do humans have?

Three—each sensitive to different wavelengths (short, medium, long).

What is the blind spot?

The point where the optic nerve leaves the eye; no receptor cells are located there.

What is the optic nerve?

The nerve that carries visual information from the eye to the brain.

What are bipolar cells?

Retinal cells that receive input from visual receptors and send it to ganglion cells.

What are ganglion cells?

Retinal cells that receive input from bipolar cells and send axons through the optic nerve.

What is the optic chiasm?

The point where the optic nerves partially cross.

What is the lateral geniculate nucleus (LGN)?

A part of the thalamus that processes most visual information before it reaches the visual cortex.

What is the primary visual cortex (V1)?

The first area of the cerebral cortex to receive visual input.

What is the simplified visual pathway order?

Retina → optic nerve → optic chiasm → LGN → visual cortex.

What is the trichromatic theory of color vision?

Color perception is based on the response rates of three types of cones.

Name the three cone types in trichromatic theory.

Short-wavelength (blue), medium-wavelength (green), and long-wavelength (red) cones.

What is the opponent-process theory?

We perceive color in terms of paired opposites: red–green, yellow–blue, white–black.

What is color constancy?

The ability to recognize colors despite changes in lighting.

What is retinex theory?

The cortex compares information from different parts of the retina to determine brightness and color.

What is lateral inhibition?

The reduction of activity in one neuron by activity in neighboring neurons, enhancing contrast.

What is a receptive field?

The part of the visual field that excites or inhibits a neuron.

What is a simple cell in V1?

A neuron that responds to a bar or edge in a particular orientation and location.

What is a complex cell in V1 or V2?

A cell that responds to a bar or edge regardless of exact location in the receptive field.

What is an end-stopped (hypercomplex) cell?

A neuron that responds to a bar of a particular length and orientation.

What is the dorsal stream of vision?

The "where/how" pathway—important for locating and interacting with objects; runs to the parietal lobe.

What is the ventral stream of vision?

The "what" pathway—important for recognizing objects; runs to the temporal lobe.

What is visual agnosia?

The inability to recognize objects despite normal vision.

What is prosopagnosia?

The inability to recognize faces.

What is motion perception?

The process of inferring speed and direction of elements in a scene.

What is area MT (middle temporal cortex)?

A brain area responsible for processing motion.

What is area MST (medial superior temporal cortex)?

Processes complex motion, such as expansion, contraction, or rotation.

What is motion blindness (akinetopsia)?

The inability to perceive motion smoothly.

What is the fusiform gyrus responsible for?

Facial recognition and object identification.

What is binocular rivalry?

Alternating perception between different images presented to each eye.

What is depth perception?

The ability to judge the distance of objects.

What are depth cues?

Features like retinal disparity, motion parallax, and linear perspective.

What is the role of experience in vision?

It shapes visual development and neural organization in the visual cortex.

What is a critical period in visual development?

A time when the brain is especially sensitive to visual input.

What happens if visual input is blocked during the critical period?

Permanent deficits in vision may occur.

What is strabismus?

A condition where the eyes do not point in the same direction.

What happens in uncorrected strabismus?

The brain suppresses input from one eye, causing poor depth perception.

What helps correct visual problems during development?

Eye exercises, glasses, or surgery if done early enough.

What is astigmatism?

A blurring of vision caused by an asymmetrical curvature of the eye's surface.

How common is astigmatism in infants?

It occurs in about 70% of infants but usually declines with age.

What is the effect of early visual deprivation in animals?

It impairs development of normal vision; neurons become unresponsive or miswired.

What did experiments on cats with one eye sewn shut show?

The deprived eye’s synapses weaken and lose input to the active eye.

What is lazy eye (amblyopia)?

Reduced vision in one eye due to disuse or dominance of the other eye during development.

How can amblyopia be treated?

Covering the stronger eye to force the weaker one to work.

What did Hubel and Wiesel discover?

That early visual experience is critical for developing the visual cortex.

What are feature detectors?

Neurons in the visual cortex that respond to specific features like edges or movements.

What happens to the visual cortex when one eye is deprived during development?

It becomes dominated by the open eye and may permanently lose responsiveness to the closed one.

What is stereoscopic depth perception?

The brain’s ability to perceive depth using input from both eyes (binocular cues).

What causes depth perception issues?

Lack of simultaneous input to both eyes, as in strabismus or amblyopia.

How does the brain represent visual information?

Through patterns of activity across populations of neurons.

What is the concept of "use it or lose it" in vision?

Neural circuits that don’t receive stimulation during development may be pruned away.

What happens to vision if both eyes are deprived early in life?

The cortex becomes unresponsive to visual input, even if the eyes are later restored.

What is neural plasticity in vision?

The brain's ability to reorganize and adapt visual processing pathways based on experience.

What is a consequence of having abnormal visual experience during development?

Poor depth perception, abnormal motion detection, or permanent visual deficits.

What is motion parallax?

A depth cue where closer objects appear to move more than distant objects during motion.

What is retinal disparity?

The difference in images between the two eyes, used for depth perception.

What is monocular vision?

Vision using one eye, which relies on cues like size, overlap, and motion.

What is binocular vision?

Vision using both eyes to perceive depth and three-dimensional structure.

What is ocular dominance?

The tendency to prefer visual input from one eye over the other.

What happens in the brain with ocular dominance columns?

Neurons are arranged to prefer input from one eye or the other in alternating patterns.

What are critical periods for ocular dominance development?

Specific times when visual input shapes the formation of ocular dominance columns.

How can ocular dominance be measured?

By recording neuron responses to stimulation of each eye.

What is cortical blindness?

Loss of vision due to damage to the visual cortex, even if the eyes are intact.

What is blindsight?

The ability to respond to visual stimuli without conscious perception, often due to V1 damage.

What causes blindsight?

Alternate visual pathways (e.g., superior colliculus) that bypass the primary visual cortex.

What is the significance of blindsight?

It shows that some visual processing occurs without conscious awareness.

What is the "binding problem" in vision?

How the brain combines features like color, shape, and motion into a unified perception.

What might solve the binding problem?

Synchronization of neural activity across brain areas.

What is the parvocellular system?

Visual pathway with small cell bodies that processes fine detail and color.

Where do parvocellular neurons project?

Mostly to the lateral geniculate nucleus (LGN) and visual cortex.

What is the magnocellular system?

Visual pathway with large cell bodies that processes motion and broad outlines.

Where do magnocellular neurons project?

To LGN, visual cortex, and other brain areas like the superior colliculus.

What is the koniocellular system?

A visual pathway with small cell bodies that projects to various layers of the LGN.

What is the role of koniocellular neurons?

They have varied functions and project to multiple areas of the visual cortex.

What is the lateral inhibition effect responsible for?

Edge detection and contrast enhancement in vision.

What causes Mach bands (illusory brightness gradients)?

Lateral inhibition exaggerating contrast at edges.

What is the Hermann grid illusion?

Gray spots appearing at intersections in a black-and-white grid, due to retinal ganglion cell response.

What does the visual system prioritize?

Edges, movement, and contrast for survival and object recognition.

What are orientation columns in V1?

Neurons arranged to respond to specific orientations of edges or bars.

What are blobs in V1?

Regions sensitive to color, part of the parvocellular input pathway.

What are interblobs in V1?

Areas between blobs involved in processing form and orientation.

What are ocular dominance columns?

Alternating bands of neurons in V1 responding to input from one eye or the other.

What are hypercolumns in V1?

Complete sets of orientation columns for both eyes at a given retinal location.

How is information processed in V1?

Through overlapping modules for orientation, spatial frequency, and eye dominance.

What is the function of area V2?

It processes further shape, color, and depth information and relays it to higher-order visual areas.

What is the function of area V4?

Processes color perception and attention modulation.

What is the function of area V5/MT?

Specialized for motion perception and direction detection.

How do areas V4 and V5 differ?

V4 focuses on color and form; V5 (MT) processes movement and motion direction.