Deck 28: Critical Periods in Sensory Systems

Question 1

Which of these is the best example of a critical period?

A) A young hawk that does not acquire hunting skills rapidly enough will likely starve to death by the end of its first year.
B) A juvenile songbird will learn to produce an abnormal song unless it is exposed to adult songs between 6 and 12 weeks of age.
C) Deprivation of social contact for at least 2 weeks, at any point in the life of a rodent, will lead to subsequent aggression and inappropriate attachment after the isolation period ends.
D) In a rodent, exposure to calcium and vitamin D during development are needed for optimal cognitive function.
E) During prenatal development, or juvenile development prior to adolescence, treatment of a female bird with androgen hormones will tend to produce male-like courtship behaviors as an adult.

Answer 1

B

Question 2

When kittens who have been reared in darkness are exposed to light, they _______, while adult cats who are exposed to light after spending a long time in darkness _______.

A) can see normally; experience blurred vision
B) experience blurred vision; experience clear vision
C) cannot see; can see normally
D) experience blurred vision; can only see diffuse illumination
E) cannot see; also cannot see

Answer 2

C

Question 3

The visual capabilities of a newborn monkey are such that

A) cortical neurons respond to specific stimuli, such as bars of light with a particular orientation, but the locations of these neurons are not yet organized in any systematic way.
B) most cortical neurons respond only to input from one eye, unlike those in adult monkeys.
C) the retina is not yet able to send visual signals to the cortex.
D) simple cells in the cortex, such as those responding to bars of light with a particular orientation, already respond similarly to those in adult animals.
E) the retina functions much like that of adults, but cortical cells respond only to diffuse light and not yet to specific stimuli.

Answer 3

D

Question 4

In young kittens reared without visual input, the "pinwheel" pattern of orientation columns

A) cannot be detected.
B) can be observed in the retina but not in the cortex.
C) can be observed in both the retina and the cortex.
D) is more pronounced than that of adults.
E) looks roughly similar to that of adults.

Question 5

Compared to adult monkeys, ocular dominance in newborn monkeys is

A) similar but less pronounced (weaker).
B) similar but more pronounced (stronger).
C) unlike adults, baby monkeys show no indication of ocular dominance.
D) ocular dominance is observed only in baby monkeys, and is eliminated by adulthood.
E) neither baby nor adult monkeys show ocular dominance.

Question 6

In newborn monkeys, the structure of ocular dominance columns

A) is virtually identical to that of adults, in all cortical layers.
B) cannot be detected in any layers (response patterns appear random).
C) is less clearly established in layer 4 than that of adults.
D) is similar to adults in layer 4, but less established in layers 1 and 7.
E) do not yet exist because all neurons respond to input from both eyes in newborns.

Question 7

This change in lateral geniculate neurons helps to produce distinct ocular dominance columns.

A) The dendrites begin to respond selectively to the most active presynaptic inputs.
B) They begin to fire action potentials only in response to input from the contralateral eye.
C) They begin to synchronize firing with the other neurons nearby.
D) The terminals branch out further to connect with a wider variety postsynaptic neurons.
E) The terminals retract or "prune" to overlap less with each other.

Question 8

The initial establishment of ocular dominance columns occurs

A) during a critical period shortly after birth and relies on visual input during that period.
B) during a critical period shortly after birth but does not need visual input during that period.
C) before birth and does not rely on visual experience.
D) shortly after birth but not during a specific critical period, relying on visual experience.
E) gradually throughout development into adulthood, relying on visual experience.

Question 9

Scientists' understanding of how segregated ocular dominance columns develop in young animals relied on the development of this experimental method.

A) Neurons in the visual system are injected with a tracer that can then be imaged in a brain slice.
B) Electrical recordings are made in the retina while a light is projected onto the photoreceptors.
C) Electrical recordings are made in the visual cortex while a second electrode stimulates the retina.
D) The visual capabilities of animals are tested using a behavioral visual discrimination task.
E) Single neurons are extracted from the visual pathway and subjected to patch-clamp recordings.

Question 10

Blockade of neural input from the retina by tetrodotoxin (TTX) has this developmental effect.

A) It prevents the formation of the pinwheel patterning in orientation columns.
B) It releases inhibition of neurons that terminate in layer 4 of the visual cortex.
C) It leads to excessive "pruning" or dearborization of LGN neurons.
D) It prevents appropriate structuring and segregation of LGN layers.
E) It has no effect on visual development.

Question 11

Cells that recognize specific types of visual stimuli such as a bar of light with a specific orientation are located in the

A) retina.
B) visual cortex.
C) optic chiasm.
D) bipolar cell layer.
E) ganglion cell layer.

Question 12

The "reverse suture" technique used to study visual development refers to

A) suturing an eyelid open so that it cannot be shut.
B) after sealing one eye shut, that deprived eye is allowed to open while the other eye is sealed shut.
C) using a temporary adhesive to seal the eye shut, which will wear off over time and allow the eye to open on its own.
D) sealing or sewing an eyelid shut.
E) administering eyedrops that dilate the pupils constantly in order to allow more light into the retina for a period of time.

Question 13

Most of the experiments reported in your textbook regarding the critical period for plasticity in visual development studied the development of

A) orientation columns in the visual cortex.
B) ocular dominance columns in the visual cortex.
C) connections between bipolar and ganglion cells in the retina.
D) receptive fields of ganglion cells in the retina.
E) motion detection.

Question 14

Eyelid closure in the first few weeks of life is an experimental technique used primarily to study the

A) critical period for plasticity of ocular dominance columns.
B) initial establishment of ocular dominance columns.
C) critical period for plasticity of orientation columns.
D) initial establishment of receptive fields of ganglion cells in the retina.
E) initial establishment of layers in the lateral geniculate nucleus.

Question 15

Which of the following techniques was not used by Hubel and Wiesel to study the role of visual experience in the development of the visual system?

A) Suturing closed the lids of one or both eyes during infancy
B) Allowing light to enter the eye, but blurring vision (e.g. by a translucent lens) during infancy
C) Producing an artificial squint
D) Rearing kittens in the presence of a single wavelength of light
E) All of the above were used by Hubel and Wiesel.

Question 16

When one eye of a newborn monkey or kitten is sutured closed for a few months, the result is that

A) pupillary reflexes are normal, but retinal ganglion cells fail to respond to light.
B) pupillary reflexes are eliminated.
C) the structure of the eye is affected, but it still produces a response to light.
D) behavior appears normal, but retinal ganglion cells do not respond to light.
E) eye structure and retinal responses appear normal, but animals behave as though that eye is blind.

Question 17

Electrical recordings in the visual cortex indicate that years after monocular deprivation in monkeys,

A) no ocular dominance columns were established; most cortical neurons responded equally to both eyes.
B) most cortical neurons responded to stimulation of the non-deprived eye, with very few responding exclusively to the previously closed eye.
C) a normal number of cortical neurons responded to stimulation of the previously-closed eye, but the response patterns were disorganized.
D) the structure and response patterns of cortical neurons were similar to those of un-deprived animals.
E) the retina of the deprived eye was still unable to respond to stimulation by light.

Question 18

Overall, when an infant's eye is sutured shut for several months during infancy, the most pronounced effects are observed in the

A) structure of the eye.
B) retina.
C) lateral geniculate nucleus.
D) primary visual cortex.
E) secondary visual cortex.

Question 19

When the eye of an infant is kept closed during infancy, the resulting change in layer 4 of the visual cortex is

A) no observable change.
B) ocular dominance columns linked to the functional eye are wider, while those linked to the closed eye are more narrow.
C) neurons corresponding to the deprived eye are more diffusely interconnected than those corresponding to the open eye.
D) cell bodies of neurons with input from the closed eye are smaller.
E) neurons corresponding to the deprived eye fire in a tonic rather than phasic pattern.

Question 20

When one eye of a kitten was sutured shut during infancy, neurons in the lateral geniculate nucleus (LGN)

A) appeared basically normal, but those with input from the deprived eye were smaller in size.
B) appeared basically normal, but those with input from the deprived eye showed much more arborization.
C) appeared virtually identical to those of animals that were not vision deprived.
D) were interspersed randomly without the usual layered structure.
E) almost all responded to input from both eyes, without the usual ocular dominance.

Question 21

An ocular dominance histogram is used to illustrate the number of

A) neurons in a brain region that respond to stimulation of each of the two eyes.
B) action potentials fired by neurons in response to stimulation of each of the two eyes.
C) neurons that are activated by different types of stimulation (e.g. an edge, a corner, a moving dot).
D) action potential fired by neurons to different levels of light.
E) neurons that are labeled by a tracer injected into the retinas of each of the two eyes.

Question 22

During normal development of the visual system in the first few weeks of life, this process appears to be responsible for the correct structuring and segregation of ocular dominance columns.

A) Cell bodies migrate from the lateral geniculate nucleus to the correct location in the visual cortex.
B) Arborization of axon terminals is reduced so that neurons innervate more specific regions of the visual cortex.
C) Arborization of axon terminals is increased so that neurons innervate larger sections of the visual cortex.
D) Lateral inhibition is established between neurons in the cortex that receive input from each eye.
E) Neurons begin to synchronize firing patterns with that of their neighbors, so that cells self-organize into groups with similar activation patterns.

Question 23

The initial establishment of ocular dominance columns _______, while ocular dominance column plasticity during the critical period _______.

A) relies heavily on visual experience; does not rely much on visual experience
B) does not rely much on visual experience; relies heavily on visual experience
C) relies heavily on visual experience; relies to a lesser degree on visual experience
D) proceeds normally without any visual experience; proceeds normally if at least one eye is open
E) proceeds normally if at least one eye is open; proceeds normally if the animal is reared in light conditions, even if both eyes are closed

Question 24

In adult monkeys, this degree of intervention is required in order to produce significant abnormalities in function of the visual cortex.

A) Closure of the eye for a few days
B) Closure of the eye for 2-3 months
C) Closure of the eye for a year
D) Removal of an eye
E) None of the above

Question 25

If one eye is sutured shut during the critical period for plasticity, under which of the below conditions will the structure and function of the visual cortex recover?

A) After the deprived eye has been open for at least twice as long as it was shut
B) After a few weeks have passed since the deprived eye was opened
C) After a few months have passed since the deprived eye was opened
D) After a least a year has passed since the deprived eye was opened
E) None of the above

Question 26

If one eye is closed during the critical period for plasticity, which of the below conditions will lead to recovery of cortical function for that eye?

A) If the deprived eye is opened, and the normal eye is then sutured shut within the critical period.
B) If the deprived eye is opened, and the normal eye is then sutured shut for the same duration that the deprived eye had been shut (at any point in the lifespan).
C) If the deprived eye is opened again before the critical period has ended.
D) All of the above conditions will lead to recovery of cortical function.
E) None of the above conditions will lead to recovery of cortical function.

Question 27

When both eyes of a baby monkey are sealed shut shortly after birth, the resulting effects on ocular dominance are

A) indistinguishable from the visual system of a normally developing monkey.
B) much more severe than the effects of sealing a single eye shut for the same duration.
C) basically the same as the effects of sealing a single eye shut for the same duration.
D) somewhat less severe than the effects of sealing a single eye shut for the same duration.
E) due primarily to changes in retinal function rather than changes at the cortical level.

Question 28

When both eyes of a newborn monkey are sutured shut for several weeks, these neurons become atrophied (the size is significantly reduced).

A) Those of the lateral geniculate nucleus
B) Those of layer 4 of the visual cortex
C) Photoreceptors in the retina
D) Ganglion cells in the retina
E) None of the above

Question 29

To produce strabismus means to

A) make a squint.
B) prevent eye movements.
C) seal the eye shut.
D) blur the vision.
E) force the eye to remain open.

Question 30

Producing an artificial squint in kittens has the same effect on the visual cortex as

A) suturing one eye shut during early development.
B) suturing both eyes shut during early development.
C) suturing both eyes open during early development.
D) covering one eye, then the other, in turns so that they are never open at the same time.
E) covering both eyes with a translucent lens that blurs images but allows light in.

Question 31

Producing an artificial squint in kittens has this result on cortical structure and/or function.

A) It reduces the number of neurons in the visual cortex that respond to only one eye.
B) It reduces the number of neurons in the visual cortex that respond to both eyes.
C) It reduces the degree of segregation of ocular dominance columns.
D) It produces atrophy of cells located in the lateral geniculate nucleus.
E) It eliminates the pinwheel structure of orientation columns.

Question 32

When monkeys were reared such that one eye was kept closed, and the other was only able to see vertical bars, this response was observed in cortical neurons.

A) The only recorded response was to vertical bars presented to the previously-open eye. No neurons responded to horizontal bars, and no neurons responded to any stimulation of the previously-closed eye.
B) Responses were observed to presentations of both horizontal and vertical bars. Similar numbers of neurons responded to the presentations of these stimuli to each eye.
C) When horizontal bars were tested, similar numbers of neurons responded to input from each of the two eyes. When vertical bars were tested, most neurons responded only to stimulation of the previously-open eye.
D) No responses were recorded to presentations of horizontal bars. Similar numbers of neurons responded to presentations of vertical bars to each eye.
E) When horizontal bars were tested, most neurons responded to binocular input. When vertical bars were tested, the only recorded responses were to stimulation of the previously-open eye.

Question 33

When tetrodotoxin is injected into both eyes of newborn kittens, this is the result.

A) Neurons projecting to the lateral geniculate nucleus failed to form layers.
B) Neurons projecting to the primary visual cortex failed to form layers.
C) Individual neurons from the lateral geniculate neurons terminate in multiple layers of the visual cortex.
D) Neurons in the lateral geniculate nucleus were significantly atrophied.
E) None of the above occurred

Question 34

Impulse activity from the retina is required in order for

A) neurons in the lateral geniculate nucleus to form appropriate layers.
B) neurons in the primary visual cortex to form appropriate layers.
C) retinal ganglion cells to establish their receptive fields.
D) synaptic connections to form between the lateral geniculate nucleus and the visual cortex.
E) neurons projecting from the lateral geniculate nucleus to arborize widely.

Question 35

Two neurotrophins involved in regulating structure and plasticity in the visual cortex are

A) nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF).
B) neurotrophic factor (NTF) and nerve growth factor 3 (NGF-3).
C) glial-derived neurotrophic factor (GDNF) and Substance P.
D) Brain-derived neurotrophic factor (BDNF) and Sonic Hedgehog (SHH).
E) Neuropeptide Y and Nerve Growth Factor (NGF).

Question 36

Transgenic over-expression of Brain-Derived Neurotrophic Factor (BDNF) in mice results in

A) a delay and lengthening in the critical period for plasticity.
B) an earlier critical period for plasticity.
C) preventing the effects of lid closure during the critical period of plasticity.
D) preventing the initial establishment of ocular dominance columns.
E) preventing normal development of ocular dominance columns during the critical period.

Question 37

Activity of _______ appears to be responsible for opening the critical period for plasticity, and activity of _______ appears to be responsible for closing the critical period.

A) cholinergic neurons; dopaminergic neurons
B) GABAergic neurons; cholinergic neurons
C) noradrenergic neurons; dopaminergic neurons
D) GABAergic neurons; GABAergic neurons
E) cholinergic neurons; cholinergic neurons

Question 38

A deficiency in GABA function early in life would be expected to have which effect on development of the visual system?

A) A reduction in ocular dominance plasticity
B) Prolonging the critical period for plasticity
C) Preventing the initial establishment of ocular dominance columns
D) Preventing the development of layers in the LGN
E) A stronger effect of monocular deprivation

Question 39

One of the factors that may be responsible for reduced plasticity after closing the critical period is a(n)

A) reduction in GABAergic activity.
B) increase in brain-derived neurotrophic factor (BDNF).
C) increase in the number of nicotinic ACh receptors in the LGN.
D) change in NMDA subunits that reduces the effectiveness of the receptor.
E) reduction in Otx2 in the retina.

Question 40

One of the "brakes" that results in closing the critical period for ocular dominance plasticity is

A) maturation of GABAergic inhibition.
B) initiation of dopaminergic activity.
C) an increase in acetylcholine production.
D) cessation of BDNF expression.
E) reduction in photoreceptor sensitivity.

Question 41

Somatosensory development of whisker barrels in rodents is similar to visual development of ocular dominance in this way.

A) Both have a critical period for plasticity that is experience dependent and relies on GABAergic inhibition.
B) Both have a critical period for plasticity that relies on NMDA receptor activity and is unaffected by TTX.
C) Both develop normally with partial sensory input (e.g. some whiskers are trimmed, one eye is closed), but do not develop normally in the complete absence of sensory input.
D) Both are established prior to birth and rely on spontaneous activity prior to any sensory experience.
E) Both are established prior to birth and can develop normally without sensory experience or spontaneous neural activity.

Question 42

The experimental disruption of olfactory sensory neurons (OSNs) as they organize onto specific glomeruli results in

A) impairments only if the disruption completely blocks neural activity, not if it involves sensory deprivation.
B) recovery no matter when the disruption occurs, due to the continued plasticity of the olfactory system.
C) no impairments because the organization of glomeruli does not depend on the OSNs.
D) long-term impairments in organization, independently of when the disruption occurs.
E) recovery if the disruption ends during a critical period, but no recovery if the disruption is after the critical period ends.

Question 43

When prisms were placed over the eyes of baby owls, so that the visual field was shifted to one side

A) the auditory map did not change and remained out of alignment with the displaced visual input.
B) the auditory map did not change, but the displaced visual map shifted back into alignment with the auditory map.
C) both the auditory map and the visual map shifted to re-align with the displaced retinal image.
D) the auditory map shifted to re-align with the displaced visual map.
E) the retina adjusted to compensate for the shift

Question 44

Some baby owls are reared in an enriched environment (Group A), and others are reared in a standard individual cage (Group B). Then, owls from both groups are fitted with goggles that used prisms to displace their vision. How would the response to the goggles in Group A be expected to differ from that of Group B?

A) Group A and Group B would not be expected to differ.
B) The auditory map in Group A will adjust to realign with the visual input, while that of Group B will not.
C) The realignment between auditory and visual input will take longer (be slower) in Group B than in Group A.
D) The realignment between auditory and visual input can occur for a longer period of time (later in life) in Group A compared to Group B.
E) The visual map in group A will adjust to the new retinal image, while the map in Group B will not.

Question 45

Cochlear implants and cataract surgery procedures represent

A) two ways in which research on developmental plasticity can be applied to human welfare
B) two experimental procedures that are commonly used to study plasticity in animal models
C) two experimental procedures that are commonly used in humans to study developmental plasticity
D) two interventions that prolong neural plasticity during development
E) two interventions that induce plasticity outside of the critical periods

Question 46

Cochlear implants are effective at allowing speech comprehension if they are implanted

A) in adults who had learned spoken language prior to deafness, or congenitally deaf children by age 3.
B) in adults, regardless of the onset of deafness.
C) in children by age 5, regardless of the onset of deafness.
D) in congenitally deaf children by age 5, or children to age 12 with milder hearing impairments.
E) prior to age 12.

Question 47

Briefly explain the concept of a critical period.

Question 48

Describe the changes that occur in the pathway from the retina to layer 4 of the visual cortex during the first few weeks after birth in a normally developing monkey.

Question 49

If an infant monkey, at 2 weeks old, and an adult monkey each have one eyelid sutured shut for 3 weeks, what differences would you expect to observe in the two individuals?

Question 50

If one eyelid of an infant monkey is sutured shut for 3 weeks during the first 6 weeks of life, under what conditions will the monkey recover normal (or nearly normal) cortical function?

Question 51

Define ocular dominance plasticity, and state two factors on which it depends.

Question 52

Describe two experimental procedures used to manipulate visual experience in young monkeys for the study of developmental plasticity. What differences were observed as a result of the two manipulations?

Question 53

Compare the relative contributions to visual system development of (1) spontaneous impulse activity in retinal neurons, and (2) activity resulting from visual experience.

Question 54

What are two neurotrophins discussed in the textbook that are involved in the critical period for ocular dominance plasticity?

Question 55

Explain the role of BDNF and GABA signaling in critical periods for ocular dominance plasticity.

Question 56

Explain the idea of molecular "brakes" on plasticity, and give one example of a "brake" on plasticity in the visual system.

Question 57

Describe one similarity between the development of ocular dominance in the visual system of monkeys, and whisker-barrel development in rodents.

Question 58

What are two ways in which research on developmental plasticity in sensory systems can be applied to human welfare?

Question 59

Compare one experimental manipulation used to manipulate sensory experience in owls with one used in monkeys. Explain the different experimental questions that prompted the use of the two procedures.

Question 60

Explain what early environmental enrichment is, and how it is thought to interact with developmental plasticity.

Question 61

Imagine two congenitally deaf infants: One is raised in a loving home with social interaction, toys, and lots of activity, while the second is raised in an impoverished orphanage, with basic food/care but little additional social interaction or activity. Both are able to receive a cochlear implant at age 3. What differences, if any, would you expect to observe in the infants' responses to the implants?

Question 62

Explain what cochlear implants are, and how they are related to the study of neural plasticity in the auditory system.