Development and Aging Flashcards
guest lectures (difference between papers)
very important
first-guest lecture dot really matter
video
- broad stuff
But first, why do we care about lifespan learning?
● Allows us to explore individual differences in development and ageing/aging
● Teaches us about plasticity
● Allows us to maximize our potential
Memory Development: Infancy to Childhood
Caveats before we begin:
● Developmental trends represent averages across considerable variability.
● Variability exists within a cohort (e.g., the huge diversity of standardized
test scores for high school seniors; diversity in language acquisition).
● Variability also exists across developmental trajectories.
Memory Development: Infancy to Childhood
mmediately after birth, human infants
demonstrate incredible learning abilities:
- Language
- Social skills
- Motor control
● Some limitations are evident due to immature sensory and motor
systems.
● Note that there is even evidence of learning in fetuses.
Non-declarative Memory in Infants?
- 2-month-old infants learned to kick to move a colourful mobile (instrumental conditioning)
● If crib liner with a new pattern was used, babies didn’t kick (context-
dependent learning)
● Human and rat infants learn eye-blink conditioning (classical conditioning)
Development of Declarative Memory?
● Declarative memory is difficult to study in young children because they do not have the verbal skills to “declare” what they remember
● Declarative memory studies are conducted in children who are old enough to speak
Development of Declarative Memory
Study:
● Children were provided with sentences:
○ “What animal can’t make any sounds?”
○ Presented by an experimenter or a puppet
● Test (1 week delay):
○ “What animal can’t make any sounds?”** (semantic memory)**
○ Semantic recall increased with age
○ Who said it (source) =episodic memory > how do children do?
Episodic Memory in Children: Who said it?
Correct source: episodic memory (improves with age)
Intra-experimental (incorrect source, mixed up puppet with experimenter) - episodic
Extra-experimental (incorrect source, thought learning of fact took place outside of lab) - episodic
4 years old: not that good with the task, they made extra-experimental error
6-8 years olds: incresed in correct source, the extra-experimental error goes down, they make more of an intra-experimental error
Sensitive Periods for Learning?
● Some learning abilities are only available or more readily available early in life, during the so-called sensitive period or critical period, after which some forms of learning may become difficult or impossible.
● Imprinting: forming a close bond with the first individual seen after birth
○ Common in birds, but also occurs in other species (some mammals)
○ Bond forms best immediately after birth; after this critical period, harder to form
Sensitive Periods for Social Attachment
● In a study, rhesus monkeys were isolated from their mothers (Harlow studies)
● In adolescence, they were moved to group cages
● Showed social deficits
● In many of these studies involving both humans and non-human animals, younger children perform better
when exposed to enriched or healthier
environments, which can alleviate certain impairments. This exposure should occur earlier in life to be most effective.
can reverse some of these imparments espessially earlier on in life
Sensitive Periods for Language
Some evidence suggests that language must be learned before approximately 12 years of age to reach true fluency.
Skills for phonetic discrimination can diminish during development for sound distinctions not utilized in the languages to which a person is exposed.
Individuals become perceptual learning experts for their language.
Although this is a subject of debate, second-language acquisition is generally believed to be easier during childhood
Adolescence: Childhood to Adulthood
● Strong development of working memory and central executive function during adolescence through adulthood
Aging Memory: Adulthood to Old Age
● Adult abilities can remain stable for many years
● Unfortunately, the overall trend is a decline in most basic memory and learning skills
● Working memory is often one of the first areas to display age-related decline
● There may be effects related to menopause
Aging Memory: Adulthood to Old Age
Similar trends are observed in non-declarative memory: Classical
conditioning begins to decline at ages 40 to 50, taking potentially twice
as long in older adults compared to young adults. Skill learning
decreases rapidly after age 60.
Aging Memory: Adulthood to Old Age
● Semantic and episodic memory exhibit an uneven decline.
● The ability to retain and retrieve older episodic and semantic memories shows less decline during healthy aging.
○ For instance, seniors who studied Spanish in high school still recall many
of the Spanish words learned, even after long periods with little practice.
● Unfortunately, the ability to form new episodic and semantic memories does decline with age.
○ These difficulties can be alleviated with slower rates of presentation
and/or meaningful stimuli.
Aging Memory: Adulthood to Old Age
Some good news: strong compensation
● Although basic skills decline, older adults have more skills and experience to draw on.
● This richer pool of experience can often help compensate for diminished skills and enable performance of complex skills at the same or better level than in young adults
The Developing Brain
● Human brain development is strongly influenced by both genes and the environment
● Human brain development features competition between cells and synapses; survival seems based on usefulness:
○ Overproduction
○ Competition for a limiting resource
The Developing Brain: Competing Neurons
● Neurons are produced very rapidly after conception
● Production is mostly complete by 25 weeks, although the connections
between neurons are not fully established.
● More neurons are produced than necessary.
● Unsuccessful neurons undergo apoptosis, or programmed cell death, which may eliminate up to one-third of the neurons initially produced.
● A similar trajectory occurs for synapses, where more are created than needed, and weaker connections are pruned accordingly
Brain Changes in Adolescence
Adolescence corresponds to changes throughout the brain, but especially in the frontal cortex.
Synaptic changes
* Strong synaptogenesis (new semantic connections), especially in the frontal cortex through adolescence,
pruning throughout early adulthood
Myelination
* Recall that axons are wrapped in myelin, improving speed and fidelity of communication between brain areas; starts after birth, not complete until around 18 years, especially in the frontal cortex
Modulation
* Dramatic increase in dopamine inputs during adolescence
The Brain from Adulthood to Old Age
● Unfortunately, even healthy aging is associated with brain deterioration, including decreased synaptic density
● The loss is uneven across brain areas and correlates with a decline in skills. The frontal cortex shows substantial loss
● Even where the number of neurons and synapses remains stable, the wiring may become less stable and functional
Barnes and colleagues investigated synaptic stability across different ages in rats.
-
Procedure:
“Place cells” in the rat hippocampus were mapped during exploration of a maze.
Rats were returned to the same maze later, and place cells were remapped.
-
Results:
For young rats, the same place cells encoded identical locations within the maze (top panel).
For older rats, the same place cells were activated in different areas of the maze (bottom panel).
Older rats maintained some level of behavioural performance in the maze but exhibited reduced stability in
the place cell firing patterns.
even if the number of neurons are simmilar,they are opperating differently.
Alzheimer’s Disease
● Alzheimer’s Disease (AD)—a form of progressive cognitive decline from accumulating brain deterioration
● AD accounts for 60-80% of all dementia cases
● AD was the 9 th leading cause of death in all Canadians in 2022 according to Statistics Canada
Exercise
● Exercise may slow the progression of age-related decline in cognition
● More research is needed!
AD progression:
- Episodic Memory Loss (recent visitors)
- Semantic Memory Loss (familiar names, locations)
- Conditioning and Skill Learning
late-stage AD, there is often a lack of awareness and daily living skills
Plaques and Tangles—Hallmarks of Alzheimer’s
Disease
Amyloid plaques = deposits of beta-amyloid (abnormal byproduct of amyloid precursor protein, kills adjacent neurons).
Plaques evenly distributed
across cortex.
Neurofibrillary tangles = collapsed protein scaffolding within neurons.
Early in AD, accumulate in hippocampus & MTL.
Hippocampal shrinkage =
early AD warning sign.
Genetic Basis of Alzheimer’s Disease?
● Several genes implicated in AD.
● Mainly related to early-onset AD (35–50 years).
● Less than 1 percent of AD cases = early-onset
● Environmental influences are important
Stroke
○ Leading cause of disability worldwide
○ Affects the arteries that communicate with the brain
○ Part of the brain cannot get the blood (and oxygen)
○ Neurons will die
Types of Stroke
● Ischemic Stroke: a blood clot in an artery obstructs blood flow. Neurons loose their oxygen and glucose supply (more common).
● Hemorrhagic Stroke: blood vessel ruptures. Neurons receive excess oxygen and other substances, which can lead to neuron death (less common)
Behavioral Consequences of Stroke
● Numbness, weakness in the face, arm, leg (one side of body)
● Sudden, severe headache
● Blurred vision
● Confusion, difficulty speaking
● Dizziness, loss of balance/coordination
● Loss of cognitive function, including learning and memory
Recovery after Brain Injury
● Recovery after brain injury ranges from subtle to significant
● Recovery can happen at all ages. Though the younger brain may be more plastic, older brains can show recovery too!
General Mechanisms
● Restoration of function of neurons that were damaged
○ Change in structure and function of undamaged neurons (e.g., new
synapses)
● Unmasking: Normally latent (silent) projections become functional following injury to other projections
○ Can help with the formation of new behavioral strategies to perform
affected functions
- the brain can reorganize itself
Principles of Recovery
● Recovery is better in infants and children(because of plasticity)
● -Developing nervous system shows more rearrangement, compensation
and growth
- e.g., stroke in infants = substantial functional recovery
Promoting Recovery
● 1. Behavioral rehab
e.g., practice, exercise, motivation
● 2. Drugs (mostly to prevent further damage; subsequent strokes)
● 3. Experimental approaches (e.g., transcranial magnetic stimulation to promote plasticity)
