IBN week 8

Is primary auditory cortex (A1) required for basic auditory discrimination?

No, basic discrimination can occur at lower levels of the auditory system

What is an important role of A1?

Processing complex sounds

Where does the dorsal auditory stream project?

Parietal cortex

What is the main function of the dorsal auditory stream?

Localizing sounds and coordinating movements toward sound sources

Where does the ventral auditory stream project?

Temporal cortex

Which task is most associated with the ventral auditory stream?

Interpreting speech and identifying complex sounds

What is the correct path of light through the eye?

Cornea and pupil → lens → retina

What is the retina?

The light-sensitive layer at the back of the eye

Which retinal cells normally generate action potentials?

Ganglion cells

Which retinal receptors are most sensitive in dim light?

Rods

Which receptors are responsible for color vision in bright light?

Cones

Where are cones most densely concentrated?

Fovea

Where are rods especially abundant?

Peripheral retina

What is the photopic visual system?

The cone-based system used in bright light and color vision

What is the scotopic visual system?

Rod-based vision in dim light

Why is rod vision generally less detailed than foveal cone vision?

Many rods converge onto shared downstream neurons

Why does the fovea support high visual acuity?

Its cone pathways preserve fine spatial detail through relatively low convergence

What is the macula?

The central region of the retina that includes the fovea

Why is the optic disc called the blind spot?

It contains no photoreceptors where the optic nerve exits the eye

What is a photopigment?

A chemical in rods and cones that responds to light

What happens to a photoreceptor when light activates its photopigment?

cGMP decreases, sodium channels close, and the cell hyperpolarizes

What do photoreceptors do in darkness?

Release neurotransmitter continuously relative to their light response

Which sequence best represents the main flow of retinal visual information?

Rod/cone → bipolar → ganglion → optic nerve

What is the role of horizontal and amacrine cells in retinal processing?

They help modify retinal signaling and contribute to lateral interactions

What is lateral inhibition?

Neurons inhibit neighboring pathways, enhancing contrast between nearby regions

Which retinal cells are especially associated with lateral inhibition?

Horizontal and amacrine cells

What is the approximate human visible wavelength range in your notes?

400-700 nm

What does trichromatic theory propose?

Color vision begins with the combined responses of three types of cones

Which cone class responds most strongly to short wavelengths?

Blue-sensitive cones

Which statement about cone responses is correct?

Cone classes have overlapping wavelength sensitivities

Approximately what proportion of human cones are short-wavelength-sensitive cones?

1-2%

If all three cone classes are stimulated in roughly balanced proportions, what color may be perceived?

White or gray, depending on overall intensity

What is the main difference between trichromatic and opponent-process theories?

Trichromatic theory explains three cone classes; opponent-process theory explains color coding in opposing channels

Which observation is explained by opponent-process theory?

A red stimulus can produce a greenish afterimage

Why might you see a greenish afterimage after staring at a red image?

Adaptation in opponent color channels creates a complementary afterimage

What is color blindness?

Impaired ability to distinguish certain colors

Why are many inherited red-green color vision deficiencies more common in males?

The relevant genes are commonly X-linked, and many red-green deficiencies are recessive

What is color constancy?

Recognizing an object's color despite changes in illumination

What does retinex theory emphasize?

The brain compares information across different regions of the visual scene to estimate color and brightness

Which statement best describes how trichromatic and opponent-process theories relate?

They explain different aspects or stages of color processing and are complementary

Which structure in the thalamus specializes in relaying visual information?

Lateral geniculate nucleus (LGN)

What is one function of the LGN beyond relaying visual information?

Controlling how much visual information reaches the cortex

Where does most visual information go after leaving the LGN?

Primary visual cortex (V1)

What is a receptive field?

The area of sensory space in which a stimulus changes a neuron's activity

What are ON-center and OFF-center receptive fields?

Visual receptive fields with different responses to light in the center versus surrounding region

If light from an object falls on the left side of the visual field, where is it primarily processed?

Primarily in the right visual cortex

Which retinal region receives light from the optic disc?

A region with no photoreceptors, producing the blind spot

What is V1?

The first major cortical area to receive visual input from the LGN

What did Hubel and Wiesel help demonstrate about neurons in visual cortex?

Different neurons respond selectively to visual features such as orientation

What does a simple cell in V1 typically respond to?

A bar or edge with a particular orientation and position

What distinguishes a complex cell from a simple cell in the classic V1 model?

A complex cell can respond to an oriented stimulus across a broader range of positions and may be sensitive to movement

A V1 neuron responds especially strongly to a vertically oriented stripe. What feature is it tuned to?

Orientation

What is spatial frequency?

How fine or coarse a visual pattern's detail is

Which pattern has higher spatial frequency?

Closely spaced alternating light and dark stripes

What does the hierarchical model of visual processing propose?

Complex visual representations are built from simpler features

What is a major limitation of a strict hierarchical model of object recognition?

It would seem to require an impractical number of highly specific neurons for every possible object or view

Which feature describes the retinotopic organization of visual cortex?

The visual field is mapped systematically across cortical tissue

Why is more cortical area devoted to central vision than to peripheral vision?

Central vision supports high-acuity, detailed processing

What is ocular dominance?

A difference in how strongly a neuron responds to input from one eye versus the other

How are orientation and spatial frequency represented in V1?

By groups of neurons selective for particular line angles and patterns of detail

What is the general function of the dorsal visual stream?

Processing spatial location and motion and guiding actions

What is the general function of the ventral visual stream?

Recognizing objects and faces and processing complex visual features

Which visual area is especially important for color perception and color constancy?

V4

What can damage to V4 cause?

Achromatopsia, an impairment or loss of color vision

A person can see an object but struggles to identify what it is. Which pathway is associated with object recognition?

Ventral visual stream

A person can recognize an object but struggles to guide their hand accurately toward it using vision. Which pathway is relevant?

Dorsal visual stream