Module 3, lecture 3

Question 1

What processes occur after neuritogenesis, synaptogenesis, and gliogenesis?

Answer 1

Myelination and synapse refinement & circuitry

These processes involve substantial structural changes and reorganization of neural circuits, paralleling the emergence and refinement of higher-order cognition and complex behavior.

Question 2

How do different life experiences affect neural circuits?

Answer 2

They cause activation of circuits and expression of behavior/motor skills

These circuits are refined as we grow.

Question 3

What happens during early postnatal life in the brain?

Answer 3

The brain increases in size via:
* elaboration of axonal and dendritic arbors and circuits
* myelination

This growth peaks due to neurogenesis just before birth.

Question 4

When does peak growth of synapses occur?

Answer 4

At 1 year old

After this peak, synapses decrease, although myelination and growth of the brain continue.

Question 5

What is the role of microglia in synaptic changes during development?

Answer 5

They prune synapses early in development

This occurs after the peak growth of synapses.

Question 6

What stabilizes activity-validated connections/synapses?

Answer 6

Astrocytes and myelination

These elements contribute to the stabilization of synapses that are validated through activity.

Question 7

What continues to increase in brain size after peak synapse growth?

Answer 7

Sinuses and myelination

This includes an increase in the number of sulci and gyri.

Question 8

What is the impact of exposure and interaction with the environment after birth?

Answer 8

It helps ensure formation and strengthening of synapses

Different experiences activate different targets and strengthen specific synapses.

Question 9

What happens if exposure to the environment is diminished?

Answer 9

Patterns of connections are changed to accommodate deficits

Other connections will be made to compensate for the loss.

Question 10

What determines the final numbers and patterns of functional connections in new neural circuits?

Answer 10

Electrical activity

This activity plays a crucial role in establishing the connections.

Question 11

What is Hebbian’s postulate?

Answer 11

Neurons that fire together wire together.

Question 12

What happens to synapses that fire synchronously?

Answer 12

They are retained and strengthened.

Question 13

What is the effect of asynchronous firing of synapses?

Answer 13

They are weakened and eliminated.

Question 14

What are the three phenomena explained by Hebbian modifications in brain development?

Answer 14

• Behaviours not initially present in newborns emerge and are shaped by experience.
• Humans have a superior capacity for acquiring complex skills and cognitive abilities during specific critical periods in early life.
• The human brain continues to grow after birth.

Question 15

What is a critical period in neural development?

Answer 15

A window in which activity can have the strongest effect on circuitry.

Question 16

During a critical period, what is maximized?

Answer 16

Acquisition or skilled execution of a particular behavior.

Question 17

What happens to synaptic connections during a critical period?

Answer 17

They are most plastic and receptive to being shaped by life experiences.

Question 18

What occurs after the critical period ends regarding synaptic plasticity?

Answer 18

Previous highly influential experiences lose their effects on synaptic plasticity.

Question 19

In which areas are critical periods common?

Answer 19

Development of sensory perception and related motor skills.

Question 20

What is a similarity between a critical period and a sensitive period?

Answer 20

Both are transient time windows during which experience exerts the strongest influence on neural circuit formation and modification.

Question 21

What happens to core features of learned behavior after the critical period?

Answer 21

They are fixed and cannot be replaced by alternative connectivity patterns.

This means that neural networks develop into a configuration that is not changeable by subsequent experiences.

Question 22

Can the neural circuits be remodeled or reshaped after the critical period?

Answer 22

No, they are fixed and cannot be changed by subsequent experiences.

This indicates that once the critical period is over, the neural configuration remains unchanged.

Question 23

How does the critical period start and end?

Answer 23

Starts and ends abruptly with a narrow time window.

An example of an endpoint is the switch from GABA as an excitatory to inhibitory stimulus.

Question 24

What is the nature of the sensitive period in neural development?

Answer 24

More flexible to remodel/reshape with a larger time window.

If key experiences fail to occur, it may be difficult but not impossible to redirect development along a typical trajectory.

Question 25

What may happen if the sensitive period experiences disruptions?

Answer 25

Function in the affected domain may not fully recover. ## Footnote However, even if remodeling isn't perfect, regular function can still be repaired.

Question 26

What can modify cortical devotion within sensory modalities?

Answer 26

Sensory experience and activity. ## Footnote An example is monocular deprivation affecting cortical territory.

Question 27

What is the effect of monocular deprivation on cortical territory?

Answer 27

Expanded cortical territory on the contralateral side. ## Footnote This shows how sensory experience influences the final arrangement of connections.

Question 28

What does ocular dominance represent in visual cortical neurons?

Answer 28

A scale from 1 (response to C eye ONLY) to 7 (I eye ONLY). ## Footnote This indicates how visual cortical neurons respond to light based on eye input.

Question 29

What was observed in normal cats regarding neuronal activity?

Answer 29

Equal/normal distribution of visual cortex response of neurons at different layers ipsilateral and contralateral. ## Footnote This shows a balanced response to visual input from both eyes.

Question 30

What happens to neuronal activity during monocular deprivation as a kitten?

Answer 30

Only neurons fed from the non-deprived eye fired. ## Footnote This occurs when deprivation happens at a critical period (2.5 months after birth).

Question 31

What is the outcome of opening the deprived eye after monocular deprivation in kittens?

Answer 31

Only responses from the ipsilateral eye are observed. ## Footnote This indicates a significant impact on circuitry due to the deprivation.

Question 32

What is the effect of monocular deprivation when it occurs in adulthood?

Answer 32

Reveals a normal distribution of neuronal activity but at much less activity. ## Footnote This shows that adult deprivation does not have the same impact as during the critical period, resulting in fewer responding cells.

Question 33

What is the critical period for language acquisition?

Answer 33

Expanded from birth to late teens (17-19 years old) ## Footnote Recent research suggests that the critical period for language acquisition is longer than previously thought, extending beyond age 7.

Question 34

How does language fluency change after age 7?

Answer 34

Fluency declines regardless of practice or exposure ## Footnote This decline in language fluency occurs even with continued practice or exposure to the language.

Question 35

Which age group learns non-native languages more quickly and fluently?

Answer 35

Children ## Footnote Children are generally more adept at acquiring non-native languages compared to adults.

Question 36

What role do GABAergic connections play in the critical period?

Answer 36

They are essential for the beginning of the critical period ## Footnote The formation of GABAergic connections marks the initiation of the critical period for language acquisition.

Question 37

What is the significance of neuromodulators in critical period plasticity?

Answer 37

They provide input that influences the shaping of the critical period ## Footnote Neuromodulators such as 5-HT, DA, NE, and ACh interact with metabotropic receptors to impact synaptic plasticity.

Question 38

What defines the end of the critical period?

Answer 38

Maturation of GABAergic neurons ## Footnote The transition from excitatory to inhibitory GABA signaling marks the conclusion of the critical period.

Question 39

What is the role of signal transduction in synaptic plasticity during the critical period?

Answer 39

Experience leads to synaptic signaling and plasticity ## Footnote This process involves changes induced by glutamate (Glu) and subsequent cellular signaling pathways.

Question 40

What are the effects of Glu-induced changes in synaptic signaling?

Answer 40

Activation of kinases and changes in gene expression ## Footnote Influx of Ca2+ through NMDA receptors triggers these changes.

Question 41

Name three proteins involved in synaptic signaling and plasticity.

Answer 41

* CREB * BDNF * Ube3a + ARC ## Footnote These proteins are crucial for various cellular processes related to synaptic strength and neuron survival.

Question 42

What neurodevelopmental disorders are associated with defects in synapse formation?

Answer 42

* Intellectual disability (e.g. Fragile-X Syndrome) * Autism spectrum disorders * ADHD * Epilepsy ## Footnote Mutations in critical period-related molecules can correlate with these disorders.

Question 43

When is the maximal effect of mutations in FMR1 protein?

Answer 43

Occurs during the critical period of synapse formation ## Footnote This highlights the importance of timing in targeting proteins for potential cures.

Question 44

True or False: Defects in synapse formation are only related to late-onset neurodevelopmental disorders.

Answer 44

False ## Footnote Defects in synapse formation, pruning, and stabilization are associated with specific critical periods of vulnerability.

Question 45

Synaptic inputs that mediate critical period plasticity in the cortex - 3 steps

Answer 45

1. Formation of GABAergic connections (start) : brain’s inhibitory neurons—they help control the activity of excitatory neurons. In early development, the brain begins forming these inhibitory connections, which are essential for setting the stage for plasticity.Without these connections, critical period plasticity cannot begin 2.Neuromodulators (e.g. 5-HT, DA, NE, ACh): help regulate brain states such as attention, arousal, and motivation. Neuromodulators fine-tune the activity of cortical circuits and help guide plastic changes by modulating when and how neurons fire. "gate" or "permit" plasticity to occur by interacting with GABAergic and excitatory systems. 3. Maturation of GABAergic neurons (end) : GABAergic neurons mature and their influence on the network strengthens.This leads to a balanced interaction between excitation and inhibition (E/I balance). Once this balance stabilizes, the brain becomes less plastic, and the critical period closes. - E/I balance

Question 46

Signal transduction

Answer 46

Experience → synaptic signalling → plasticity

Question 47

Glu-induced changes via (Signal transduction essential for critical period synaptic plasticity)

Answer 47

influx of Ca2+ → activation of Ks → changes in gene expression: - BDNF: activate several cell- survival cascades - Ube3a + ARC: regulate AMPA-R trafficking strengthening or weakening synapses e.g. Fos e.g. BDNF