1
Q
The main sensory organ of the visual system is the ______, which takes in the physical stimuli of _____ and ______ them into electrical and chemical signals that can be interpreted by the brain to construct physical images.
A
The main sensory organ of the visual system is the eye, which takes in the physical stimuli of light rays and transduces them into electrical and chemical signals that can be interpreted by the brain to construct physical images.
2
Q
The eye is divided into anterior and posterior segments (cavities). Describe the location and strucutres included in each segment.
A
Anterior segment/cavity - front 1/3 of eye; incl structures in front of vitreous humour: cornea, iris, ciliary body, lens, and aqueous humour.
- Composed of two spaces: anterior and posterior chambers.
Posterior segment/cavity - back 2/3 of eye; incl vitreous humour, retina, choroid, and optic nerve.
3
Q
The anterior chamber is filled w __________, wh provides pressure to maintain shape of eyeball and nourishes the ____ and ____.
A
The anterior chamber is filled w aqueous humour, wh provides pressure to maintain shape of eyeball and nourishes the cornea and iris.
4
Q
Which structure lines the inside of eyelids and covers/nourishes/protects the sclera and cornea?
A
Conjunctiva – thin layer of cells that lines inside of eyelids and covers/moisturizes/protects sclera (whites) and cornea.
5
Q
The ______ is the transparent covering over iris/pupil/ant. chamber; starts to refract light, first part of eye light hits.
A
The cornea is the transparent covering over iris/pupil/ant. chamber; starts to refract light, first part of eye light hits.
- Thick sheet of fibrous tissue
- Works t/g w ant. chamber and lens to refract light.
- Cornea accounts for ~2/3 of eye’s total optical power.
- Humans: refractive power of cornea is ~43 dioptres.
- Can be surgically reshaped, e.g. LASIK
6
Q
Which structure accounts for the majority of the eye’s refractive power?
A
The cornea, ant. chamber, and lens work t/g to refract light, but the cornea accounts for ~2/3 of eye’s total optical power.
- Humans: refractive power of cornea is ~43 dioptres.
- Can be surgically reshaped, e.g. LASIK
7
Q
The pupil is the opening in the middle of the iris. How does the size of the pupil change, and how does this affect the amount of light entering eye?
A
Pupil - opening in middle of iris; size of pupil changes based on iris relaxing/contracting; modulates amount of light that enters.
- As iris contracts → pupil size ↓ → amount of light ↓
8
Q
Describe the structure and function of the iris.
A
Iris - Gives the eye color; muscle that constricts/relaxes to change size of pupil → modulates amount of light entering eye (“accommodation”).
- Iris contracts → pupil size ↓ → less light enters eye.
- Location: anterior chamber of anterior segment.
9
Q
The _______ is the narrow region behind iris and in front of lens; also filled w aq humour.
A
The posterior chamber is the narrow region behind iris and in front of lens; also filled w aq humour.
- Part of anterior segment (front 1/3 of eye).
10
Q
Describe the structure and function of the lens.
A
Lens - transparent, biconvex; refracts light → focuses onto retina.
- Adjusts focal distance of eye via accomodation, i.e. changes shape (curvature/thickness) using suspensory ligaments to focus objects at various distances onto retina.
- Accounts for ~1/3 of refractive power of eye; ~18 diopters.
- Recall: cornea accounts for ~2/3; ant chamber makes up minor balance.
11
Q
The eye can adjust focal distance via a process called accommodation. Describe how this process works.
A
Short focal distance:
- Ciliary muscle contracts → zonule fibers loosen → lens thickens (more round) → higher refractive power.
Long focal distance:
- Ciliary muscle relaxes → zonule fibers tighten→ lens thins (more flat) → less refractive power.
12
Q
To focus on a distant object, ciliary muscles must (contract/relax) → zonular fibers (tighten/loosen) → lens becomes (thick & round/thin & flat) → refractive power (↑/↓) → focal distance (↑/↓).
A
To focus on a distant object, ciliary muscles must relax → zonular fibers tighten → lens becomes thin & flat → refractive power ↓ → focal distance ↑.
13
Q
The ___________ is a ring of smooth muscle that controls accommodation (adjusts focal distance) and regulates secretion of aqueous humour.
A
The ciliary muscle is a ring of smooth muscle that controls accommodation (adjusts focal distance by changing shape of lens) and regulates secretion of aqueous humour.
- Suspensory ligaments - attached to a ciliary muscle → combine to form ciliary body.
- Note: pupil size changes via sphincter pupillae muscle and dilator pupillae; ciliary muscle not involved.
14
Q
The __________ is the space b/w the lens and retina; filled w __________, wh provides pressure/nourishes posterior segment of eye.
A
The vitreous chamber is the space b/w the lens and retina; filled w vitreous humour, wh provides pressure/nourishes posterior segment of eye.
- Vitreous humor - transparent, colorless, gelatinous mass; comprises 4/5 volume of eye.
15
Q
What is the term for the region along back of eye where phototransduction occurs, i.e. light → neural impulse → perception.
A
Retina - region along back of eye where phototransduction occurs, i.e. light → neural impulse → perception.
- Contains three layers of neural cells: photoreceptors (rods/cones), bipolar cells, and ganglion cells.
- Rods - dim; black/white.
- Cones - light; color.
- Retinal blood vessels create “red-eye” effect in photos.
16
Q
What are the macula and fovea?
A
Macula – region of retina directly behind lens, center of wh is the fovea; rich in cones, some rods.
Fovea – small indentation in center of macula; completely covered in cones, no rods.
- FOvea, COnes.
17
Q
Describe the structure, function, and location of the choroid.
A
Choroid - vascular layer b/w retina/sclera; provides O2/nutrients.
- Thickest at rear of eye; narrow elsewhere.
- Forms uveal tract, along w ciliary body and iris.
- Humans: pigmented black → all light is absorbed.
- Other animals (e.g. cats) have reflective/unpigmented choroid → enhances night vision
18
Q
Describe the structure and function of the optic nerve.
A
Optic nerve (cranial nerve II) - carries visual info fr retina to brain.
- Composed of retinal ganglion cell axons and glial cells.
- Extends fr optic disc to optic chiasm.
- Optic disc/nerve head - point of exit for ganglion cell axons; no photoreceptors → blind spot.
- Optic chiasm - part of brain (below hypothalamus) where optic nerves partially cross.
19
Q
What is the term for the “white of the eye”?
A
Sclera - white of eye; thick, fibrous tissue; covers posterior 5/6th of eye (cornea covers anterior 1/6); attachment point for muscles; extra layer of protection; lined w conjunctiva.
- Humans: rare for having plainly discerible iris against sclera → easier to infer where another individual is looking → cooperative eye hypothesis suggests this has evolved as a method of nonverbal comm.
20
Q
What condition involves the ability to see things up close, but not from far away?
A
Myopia = nearsightedness, i.e. ability to see things up close, but not fr far away.
- Lens has too much refractive power, i.e. light reflects off of a far away object → refracts via cornea/lens → creates image that falls in front of retina rather than directly ON retina.
- Correct w diverging lens (negative power), e.g. glasses wh ↓ total refractive power of eye.
- Most common eye problem; ~1.5 bil (22% of population)
21
Q
What condition involves the ability to see things from far away, but not up close?
A
Hyperopia = farsightedness, i.e. ability to see things far away, but not close.
- Lens has too little refractive power, i.e. light reflects off close up object → refracts via cornea/lens → creates image that falls behind retina rather than directly ON retina.
- Correct w convex lens (positive power), e.g. glasses wh ↑ total refractive power of eye.
22
Q
What are emmetropia and presbyopia?
A
- Emmetropia - normal vision
- Presbyopia - inability to accommodate (focus); results fr loss of flexibility of lens, wh occurs w aging.
23
Q
What is a diopter?
A
Diopter - unit of measurement of optical power of a lens/curved mirror.
- Reciprocal of the focal length in metres; 1 diopter = 1 m-1.
- I.e. a unit of reciprocal length.
- E.g. a 3-diopter lens brings parallel rays of light to focus at 1/3 meter.
- E.g. a flat window has an optical power of zero diopters.
24
Q
__________ is the electrical activation of one neuron by another neuron.
A
Transmission is the electrical activation of one neuron by another neuron.
25
\_\_\_\_\_\_\_\_ is the conscious sensory experience of neural processing.
**Perception** - conscious sensory experience of neural processing.
26
\_\_\_\_\_\_\_\_\_\_ refers to energy transformation in wh light energy is transformed into electrical energy by photoreceptors.
**Phototransduction** refers to energy transformation in wh light energy is transformed into electrical energy by photoreceptors.
27
What type of physical stimuli is light?
**Light is an electromagnetic wave**.
* EM spectrum ranges fr gamma rays (short wavelength) to AM/FM (long).
* Visible light: 700nm-ROYGBV-400nm.
28
Photoreceptors in the eye include rods and cones (and photosenstive retinal ganglion). Describe the functions that rods and cones serve.
* **Rods** - **dim** light; **black/white**; **peripheral** vision
* **More abundant than cones** (~90-120M per retina vs 6-7M).
* Located mostly on retinal periphery (hence peripheral vision)
* **1000x more sensitive to light** than cones.
* Slow recovery time (think about adjusting to darkness)
* **Cones** - **daytime**/**color**/**detail**
* Less abundant (~6-7M per retina).
* Almost all are centered in **fovea** (recall: dimple in center of macula of retina).
* Trichromatic theory: 3 types: S-, M-, and L-cones (short/med/long wavelength) → RGB color vision.
* Less sensitive, but fast recovery time (fire more freq).
29
What function do bipolar neural cells serve in the eye?
**Bipolar cells** - transfer visual signals (electrical impulse) fr photoreceptors to retinal ganglion cells.
* **Inhibited/excited** by changes in amount of **glutamate** released by photoreceptors.
* Diff bipolar cells respond to diff receptive fields.
30
What function do retinal ganglion cells serve?
**Ganglion cells** - sensory neurons that receive signals fr bipolar cells and sends AP down axons to optic nerve.
* Recall: **optic nerve** - carries visual info fr retina to brain; extends fr optic disc to optic chiasm; contains retinal ganglion axons and glial cells.
* Travels to lateral geniculate nucleus (LGN) of thalamus, wh preserves the visual map created by ganglion → projects info to primary visual cortex in occipital lobe.
* Some axons fr ea eye cross to opp side of brain.
31
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is the sensory transduction of visual system in wh light is converted into electrical signals.
The **visual phototransduction cascade (vPTC)** is the sensory transduction of visual system in wh light is converted into electrical signals via photoreceptors: rods/cones, and photosensitive retinal ganglion cells.
* Photons enter eye → rod switches OFF → bipolar cell switches ON → retinal ganglion cell (optic nerve) switches ON → thalamus → occipital lobe.
32
How are rhodopsin, retinal, and transducin related to rod photoreceptor cells?
**Rhodopsin** - membrane protein (G-protein coupled receptor) in rod cells; binds a **chromophore** (**11-*cis* retinal**: aldehyde of vit A1) and **transducin** (Gt; protein);
* **Cones contain photopsin**/cone opsin instead of rhodopsin; **α subunit of transducin is also diff**.
33
Photoreceptor cells are unusual in that they (depolarize/hyperpolarize) in response to absence of stimuli and (depolarize/hyperpolarize) in light.
Photoreceptor cells are unusual in that they **depolarize** in response to **absence** of stimuli and **hyperpolarize in light**.
* I.e. rods/cones are switched ON by default.
* Scotopic conditions - absence of stimuli, i.e. darkness
* Photopic conditions - high light levels.
* Mesopic - dawn/dusk; both rods/cones involved.
34
Summarize the visual phototransduction mechanism in the presence of light.
**Summary: light absorption ↑ → [cGMP] ↓ → cell hyperpolarizes → glutamate release ↓ → excites ON-bipolar cells → signal transmitted**.
* Retinal (bound to rhodopsin) changes fr 11-cis (bent) to all-trans (straight) → causes rhodopsin to change shape → activates transducin → transducin dissociates fr rhodopsin and its α subunit binds to phosphodiesterase (PDE; another disk protein) → PDE converts cGMP into GMP
* **As light absorption ↑, [cGMP] ↓.**
* cGMP levels are low → cGMP-gated Na+ channels close → IC [Na+] ↓ (dark current switches OFF) → cell hyperpolarizes → v-gated Ca2+ channels close → IC [Ca2+] ↓ → glutamate release ↓ → excites (depolarizes) rod/cone ON-center bipolar cells & inhibits (hyperpolarizes) cone OFF-center bipolar cells → signal transmitted to ganglion, optic nerve, thalamus, occipital lobe.
* Note: resting mem potential is about -40mV, so when cGMP-gated Na+ channels close, the efflux of K+ thru leakage channels causes hyperpolarization (i.e. more negative).
35
Summarize the visual phototransduction mechanism in the absence of light.
**Summary: light absorption ↓ → [cGMP] ↑ → cell depolarizes → glutamate release ↑ → inhibits ON-bipolar cells → no signal transmitted**.
* Retinal remains 11-cis shape → transducin remains bound to rhodopsin → phosphodiesterase (PDE) remains inactivated by transducin → cGMP not converted into GMP.
* **As light absorption ↓, [cGMP] ↑.**
* cGMP levels are high → cGMP-gated Na+ channels open → IC [Na+] ↑ (inward/"dark" current switches ON) → cell depolarizes.
* → v-gated Ca2+ channels open → IC [Ca2+] ↑ → glutamate release ↑ → inhibits (hyperpolarizes) rod/cone ON-center bipolar cells & excites (depolarizes) cone OFF-center bipolar cells → no signal transmitted to ganglion, optic nerve, thalamus, occipital lobe.
36
If ON-center bipolar cells are excited (depolarized), what does this indicate about the amount of light present?
If ON-center bipolar cells are excited (depolarized):
* As **light absorption ↑ → [cGMP] ↓ → cell hyperpolarizes → glutamate release ↓ → excites ON-bipolar cells → signal transmitted.**
* I.e. mesopic (dawn/dusk) or photopic (high light) conditions.
37
If ON-center bipolar cells are inhibited (hyperpolarized), what does this indicate about the amount of light present?
If ON-center bipolar cells are inhibited (hyperpolarized):
* As **light absorption ↓ → [cGMP] ↑ → cell depolarizes → glutamate release ↑ → inhibits ON-bipolar cells → no signal transmitted**.
* I.e. mesopic (dawn/dusk) or scotopic (v low light) conditions.
38
In the dark, transducin—a regulatory protein—remains bound to rhodopsin. What effect does this have on cGMP levels?
Summary: light absorption ↓ → [cGMP] ↑ → cell depolarizes → glutamate release ↑ → inhibits ON-bipolar cells → no signal transmitted.
* If transducin remains bound to rhodopsin, then PDE is not activated and less cGMP is converted into GMP. Thus, **cGMP levels are high**.
39
T/F: rod photoreceptor cells depolarize as light absorption ↑ and cGMP levels ↓.
False
Rod photoreceptor cells **hyperpolarize** as light absorption ↑ and cGMP levels ↓.
40
All of right visual field goes to left side of brain, and all of left visual field goes to right side of brain. Describe the structures involved in this crossover.
Light from the left half of the visual field hits the nasal side of the left eye and the temporal side of the right eye; and vice-versa: right visual field → nasal right eye & temporal left eye.
* Recall: the optic nerve fr ea eye converges at the optic chiasm and splits again, creating an X-shape.
* Axons fr nasal side of BOTH eyes cross to the opposite optic nerve at the optic chiasm; temporal axons do not cross.
* **As a result, all of *left* visual field (left nasal & right temporal) goes to *right* side of brain, and** **all of *right* visual field (left temporal & right nasal) goes to *left* side of brain.**
41
Neurons project fr the visual cortex along two visual pathways, wh detect diff features of visual stimuli. Wh pathway projects to the parietal cortex and is more involved in perceiving the location of objects?
**Dorsal (“where”) pathway** - projects to the **parietal** cortex and is more involved in perceiving the **location** of objects.
* Communicates w ventral pathway ("what"; temporal lobe) → integrated elsewhere in brain.
42
Neurons project fr the visual cortex along two visual pathways, wh detect diff features of visual stimuli. Wh pathway travels to the temporal lobe towards the base of the brain and is involved in object recognition?
**Ventral** (“**what**”) **pathway** - travels to the temporal lobe towards the base of the brain and is involved in object recognition.
* Communicates w dorsal pathway ("where"; parietal cortex) → integrated elsewhere in brain.
43
Feature detection theory posits that specific neurons (feature detectors) fire in response to diff stimuli. What are the three key features detected?
**Color, form, and motion**.
Think: Teeny tiny turtle on a scooter yelling "**C**an't **F**ind **M**e".
44
Briefly describe the trichromatic and opponent process theories of color vision.
**Trichromatic** - cones receptive to **3 colors** (**RGB**) → **mix** t/g → perceive color.
* 60% red cones, 30% green, 10% blue.
* Problem: Our eyes can mix R/Y → orange, but can't seem to mix R/G or B/Y.
**Opponent Process** - cones receptives to **4 colors** (**RGB+Y**) → **opposing color pairs, one dominates** **and sends AP** → perceive color.
* R and G oppose ea/o, as do B and Y
* Black/white (rods) also oppose
* Only one color can dominate at a time.
45
What does the parvocellular pathway encode?
**Parvocellular pathway** – encodes **FORM** (think **P**ink **P**yramid = color/form = **P**arvo)
* **High spatial resolution**, i.e. boundaries, shape, levels of detail
* **Good color resolution**; cones involved.
* Poor temporal resolution, i.e. can't detect motion.
46
What does the magnocellular pathway encode?
**Magnocellular pathway** - encodes **MOTION** (think **M**agno = **M**otion).
* **High temporal resolution**
* Poor spatial resolution
* No color resolution, hence no cones involved.
47
What is meant by the term "parallel processing" of visual stimuli?
**Parallel processing** – **integrate all info** (**c**olor, **f**orm, **m**otion) at **same time**; i.e. 2+ mental processes carried out simult.
* **Occipital lobe** - constructs a holistic image by integrating all sep elements of an object; **also adds stored (experiential) info**.
48
The tri-chromatic theory of color vision describes the types of cones. Which of these is NOT a type of cone in humans?
* Yellow
* Green
* Blue
* Red
The tri-chromatic theory of color vision describes the types of cones. Which of these is NOT a type of cone in humans?
* **Yellow**
* Green
* Blue
* Red
49
Which of these is the correct order to the steps of the phototransduction cascade in reaction to light?
* A rod turns from on to off =\> turns a bipolar cell off-center =\> activates a retinal ganglion cell.
* Retinal changes conformation =\> α unit bonds with PDE =\> the rod hyperpolarizes and turns on.
* A rod changes conformation =\> α unit bonds with PDE =\> the rod hyperpolarizes and turns off.
* A rod turns from on to off =\> turns a bipolar cell on-center =\> activates a retinal ganglion cell.
Which of these is the correct order to the steps of the phototransduction cascade in reaction to light?
* A rod turns from on to off =\> turns a bipolar cell off-center =\> activates a retinal ganglion cell.
* ...ON-center...
* Retinal changes conformation =\> α unit bonds with PDE =\> the rod hyperpolarizes and turns on.
* ...rod hyperpolarizes and turns *OFF*.
* A rod changes conformation =\> α unit bonds with PDE =\> the rod hyperpolarizes and turns off.
* *Retinal* and *rhodopsin* change conformation...
* **A rod turns from on to off =\> turns a bipolar cell on-center =\> activates a retinal ganglion cell**.
50
The blind spot is the area where the optic nerve connects to the retina. The ‘night blind spot’ occurs under conditions of low light and can extend 5 to 10 degrees from the center of the person’s field of view. What is the cause of the ‘night blind spot’?
* Mesopic vision, used in low light, does not receive input from the fovea due to the lack of rods.
* Photopic vision, used in low light, does not receive input from the fovea due to the lack of rods.
* Scotopic vision, used in low light, does not receive input from the fovea due to the lack of rods.
* Scotopic vision, used in low light, does not receive input from the fovea due to the lack of cones.
The blind spot is the area where the optic nerve connects to the retina. The ‘night blind spot’ occurs under conditions of low light and can extend 5 to 10 degrees from the center of the person’s field of view. What is the cause of the ‘night blind spot’?
* Mesopic vision, used in low light, does not receive input from the fovea due to the lack of rods.
* Photopic vision, used in low light, does not receive input from the fovea due to the lack of rods.
* **Scotopic vision, used in low light, does not receive input from the fovea due to the lack of rods**.
* Scotopic vision, used in low light, does not receive input from the fovea due to the lack of cones.
51
Scientists selectively reared kittens in either an environment with lines of only vertical or only horizontal orientation. After 5 months, the scientists recorded from neurons in the cats’ cortex and found many neurons which responded to vertical lines in vertically reared cats, but no neurons that fired to horizontally oriented lines. The opposite occurred in horizontally reared cats; Horizontally reared cats had many neurons that responded to horizontal lines, but none that responded to vertical lines. What has likely happened to the cats?
* The cats habituated to the environment, but were able to adjust quickly to a different environment.
* Horizontally reared cats were bred to attend only to horizontal lines in their environment.
* The cats learned to adapt to their environment through experience-dependent plasticity.
* Vertically reared cats had no need to learn about horizontal lines and chose not to learn about them.
Scientists selectively reared kittens in either an environment with lines of only vertical or only horizontal orientation. After 5 months, the scientists recorded from neurons in the cats’ cortex and found many neurons which responded to vertical lines in vertically reared cats, but no neurons that fired to horizontally oriented lines. The opposite occurred in horizontally reared cats; Horizontally reared cats had many neurons that responded to horizontal lines, but none that responded to vertical lines. What has likely happened to the cats?
* The cats habituated to the environment, but were able to adjust quickly to a different environment.
* Habituation implies that the stimulus was presented multiple times, but was not there originally.
* Horizontally reared cats were bred to attend only to horizontal lines in their environment.
* Selectively *rearing* an animal is very different from *breeding*.
* **The cats learned to adapt to their environment through experience-dependent plasticity**.
* Vertically reared cats had no need to learn about horizontal lines and chose not to learn about them.
* The cats are not making any conscious choices about what they learned about the environment.
52
The figure shown is called a Necker cube. Opposite sides are parallel, and the cube’s orientation is ambiguous, alternating between the front face being the lower left or the upper right. Which cognitive mechanism creates this illusion?
* Divided attention
* Selective attention
* Joint attention
* Directed attention
The figure shown is called a Necker cube. Opposite sides are parallel, and the cube’s orientation is ambiguous, alternating between the front face being the lower left or the upper right. Which cognitive mechanism creates this illusion?
* Divided attention
* Divided attention occurs when an individual must perform two tasks which require attention, simultaneously.
* Selective attention
* Selective attention is the ability to maintain attention while being presented with masking or interfering stimuli.
* Joint attention
* Joint attention is the focusing of attention on an object by two separate individuals.
* **Directed attention**
* Directed attention allows attention to be focused sustainably on a single task, in this case a single orientation of the Necker cube.
53
What is the term for the process of creating electrical energy in response to light?
* Transmission
* Processing
* Perception
* Transduction
What is the term for the process of creating electrical energy in response to light?
* Transmission
* electrical activation of one neuron by another neuron.
* Processing
* neural transformation of mutliple neural signals into a perception.
* Perception
* conscious sensory experience of neural processing
* **Transduction**
54
Pilots need accurate night vision to see effectively both inside the cockpit and to scan the sky for other aircraft. Pilots are advised to “close one eye when using a light to preserve some degree of night vision”. Why is this?
* Light adaptation is lost very slowly because the pigment rhodopsin is bleached.
* Light adaptation is lost very quickly because the pigment S-wave sensitive opsin is bleached.
* Dark adaptation is lost very slowly because the pigment L-wave sensitive opsin is bleached.
* Dark adaptation is lost very quickly because the pigment rhodopsin is bleached.
Pilots need accurate night vision to see effectively both inside the cockpit and to scan the sky for other aircraft. Pilots are advised to “close one eye when using a light to preserve some degree of night vision”. Why is this?
* Light adaptation is lost very slowly because the pigment rhodopsin is bleached.
* Light adaptation is lost very quickly because the pigment S-wave sensitive opsin is bleached.
* Dark adaptation is lost very slowly because the pigment L-wave sensitive opsin is bleached.
* **Dark adaptation is lost very quickly because the pigment rhodopsin is bleached**.
Light adaptation happens when one moves from a dimly lit area to a brightly lit area.
Dark adaptation occurs when one moves from a brightly lit area to a dark area.
55
Many senses can contribute to the sensation of vertigo. Which of these statements describes a sense that is NOT contributing to postural control?
* The visual system sends information confirming the body’s position relative to other objects in space.
* Input from nociceptors, which help the body react to gravity.
* Sensory input from the vestibular system helps the individual maintain balance.
* Neurons in skeletal muscle inform the proprioceptive system about the body’s position in space.
Many senses can contribute to the sensation of vertigo. Which of these statements describes a sense that is NOT contributing to postural control?
* The visual system sends information confirming the body’s position relative to other objects in space.
* **Input from nociceptors, which help the body react to gravity.**
* Sensory input from the vestibular system helps the individual maintain balance.
* Neurons in skeletal muscle inform the proprioceptive system about the body’s position in space.
56
Which of these is an attribute of the magnocellular pathway?
* High temporal resolution
* Sharp, high feature resolution
* Poor object tracking
* High spatial resolution
Which of these is an attribute of the magnocellular pathway?
* **High temporal resolution**
* Sharp, high feature resolution
* Poor object tracking
* High spatial resolution
57
Marr’s stages of vision describes how a 2D image on the retina is transformed to a 3D object. Which of these is NOT one of Marr’s 4 stages of vision?
* Primal Sketch
* 3D object-centered description
* 1D sketch
* 2.5D sketch
Marr’s stages of vision describes how a 2D image on the retina is transformed to a 3D object. Which of these is NOT one of Marr’s 4 stages of vision?
* Primal Sketch
* In the primal sketch stage, edges, and texture are identified and used to create a basic scene outline.
* 3D object-centered description
* In the 3D object-centered description stage, the object is able to be recognized from any angle or visualized as a 3D map.
* **1D sketch**
* The Marr’s first stage of vision is called either the **grey level description** or the **input image**, not 1D sketch.
* 2.5D sketch
* In the 2.5D sketch stage, surfaces and scenes are related to one another.
MCAT Psych - DTR
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