Psych 351C: Midterm 3 Review (Development and Plasticity)

Neurulation

Establishment of neural tissue, occurs when neural plate transforms into neural tube around 16-18 days post conception

What does the neural tube form

Forms the ventricles and spinal canal, cells around the tube will become brain tissue

Neurogenesis

Occurs around 7 weeks in the periventricular zone, it is the creation of neurons

T or F: neurogenesis only occurs in embryo’s

F, slows down as birth approaches, but there is evidence that it occurs in hippocampus throughout adulthood

Migration of neurons

Cells formed during neurogenesis travel along radial glial body to brain surface, finished by around 6 months

Each successive wave of neurons migrate farther from ventricles (newest farthest out)

Synaptogeneis

Occurs just after birth, it is a massive (ten-fold) increase in number of synapses (7.3 million per minute)

Makes unnecessary amount of synapses that get prunned

Does pruning occur at the same time for all brain areas

No, occurs at different times for different brain areas with more complex areas being pruned earlier

When does pruning occur for somatosensory, association cortices and the PFC

Somatosensory - quickly and early (2 m), finished by 4 years

Association cortices - moderately quickly and early (7 m), finished by 10 years

PFC - Slowly, right after birth to mid twenties

Myelination

Myelin covering areas of the brain, brain is relatively unmyelinated at birth

DMN in adult and children study and conclusion

Had child and adult participants do the same task that uses DMN and looked at areas of activation, saw adults had consistent DMN activation, but children did not

Concluded children cannot form long range connections

What was the problem with DMN adult/children study

Did not account for children moving in the scanner

With movement controlled for, saw DMN activation in children beginning in early infancy, but improving as one ages

What are the two main systems that explain plasticity

Experience-expectant systems

Experience-dependent systems

Experience-expectant systems

Neural systems that respond to universally present experiences

Relies on external information for development, so lack of experience leads to lacking development

Experience-dependent systems

Neural systems that vary across people based on personal experiences

Says that experiences are not necessary for typical development, that they reflect plastic changes in environment

Enriched/barren environment experiment

Had two groups of animals, one that is placed in barren environment and other in enriched environment and looked at differing cognitive/neural development

What were the 2 findings for animals placed in enriched environment at a young age

1. Had lifelong structural changes to neural circuits such as increased dendritic arborization

2. Better performance on cognitive tasks

What was found for animals placed in enriched environment when they were older, and the conclusion from it

Saw improvement but less meaningful and long lasting, concluded there is a sensitive period for growth

Sensitive period

Specific time during development when organism is particularly responsive to certain stimuli

What was found regarding english speakers who moved to the US prior to age 6 or following age 6

Prior - could speak english as well as a native speaker

After - could never achieve mastery, performance decreasing as age of move increased

T or F: Sensitive period are approximately the same for all cognitive abilites

F, vary widely with memory typically peaking at about 4 years, and knowledge peaking far into adulthood

What is the sensitive period for speech/sound

Infancy, children can discriminate phonemes in every language, regardless of their caregivers native language

Perceptual narrowing

The shaping of perceptual abilities in response to environmental input

What is found when children and adults are asked to choose between two options

Children - will always pick the outcome that maximizes potential reward

Adults - will pick based on whatever has highest probability of success

T or F: Children are not susceptible to the Ebbinghause illusion

T, likely because illusion is based on world knowledge of perspective that they have not yet developed

Plasticity

The ability for the brain to modify itself to experiences, based on addition/reduction of synapses

Could be adaptive or maladaptive

Recovery vs Compensation

True Recovery - original function is restored, can take weeks to months

Compensation - person learns work around to do task in new way, can take months to years

Hemispherectomy

When someone has half of their brain removed due to extreme epileptic seizures

Only done in childhood, as they are able to adapt better

What happens if an adult and child had a hemispherectomy

Child - develop with some abnormalities, but retain motor/sensory ability and language

Adult - Lose language, motor functioning and many other things

Kennart principle

the more early a lesion is made the more likely there is compensatory plasticity

Based on idea that young brain is more equipped to reorganize, especially if damage is prior to end of sensitive period

What is the major problem with the Kennard principle

Evidence is based on motor cortex, but different brain areas have different sensitive periods

Morris water maze task experiment

Lesioned rats mPFC at day 3, day 10 or as adults and had them perform the morris water maze task (find and remember underwater platform)

What were the findings of the Morris water maze task experiment

Rats lesioned at day 3 showed impairment, but day 10 lesions produced best adaptation

demonstrates that Kennard principle is not true in general

T or F: rats in an enriched environment show reduced dendritic branching over time in the somatosensory cortex

T, u-curve shape in primary somatosensory cortex

What are the 3 age related factors that affect recovery with regard to children’s brains

1. Age child sustains lesion

2. Amount of time passed since injury

3. Age at which child is assessed

May cause deficit to occur later, when region becomes needed

Crowding hypothesis

Deficits seemingly occur at random time since brain area must carry out usual expected duties as well as duties of damaged area

Two types of plasticity

Adaptive plasticity - cortex repurposed to subserve new functional action (e.g. losing a finger, area related to finger re-used)

Maladaptive plasticity - neurons used to code for something are now being supplied nerves (innervated) by input from other regions (e.g. how phantom pain arises)

What cognitive areas are impaired and sustained in older adults

Impaired - Explicit episodic memory, speed processing, WM, LTM

Sustained - Knowledge, implicit memory, vocabulary

What are two different cognitive strategies that older adults use

Positive attentional bias (focus more on positive), and get over bad moods quicker

T or F: Adults do not have reduced brain volume

F, see reduced volume in frontal and MTL regions, sensory cortices spared

Dedifferentation

Theory that neural localization of function becomes less defined with age

Developed as older adults show more diffuse patterns of activation when performing cognitive task

Compensation

Theory that older adults may over-recruit the same brain regions as young adults, or recruit different regions to achieve similar tasks

What areas did older adults recruit for WM and attention tasks and what does it suggest

WM - recruited contralateral PFC

Attention - recruited left PFC regions

Due to relying on contralateral regions, may be that older adults are impaired on local processing

What two areas do we see WM reduction in adults, and what does it cause

WM is reduced across the brain, but two areas are special

Frontal reduction - associated with poorer cognitive control

Temporal reduction - associated with poorer episodic memory

Cognitive reserve

Theory that partaking in actives that improve brain health will lead to a greater brain reserve capacity

Increased capacity means more damage needs to occur for one to reach functional impairment cutoff, and thus show cognitive deficits

Explains why some older adults more cognitively healthy than others, despite similar damage

Hyperbinding

Theory that older adults bind too much info even if it is irrelevant, leading to them having difficulty focusing on one task and ignoring others