Infant, child, adolescent and ageing brain

Question 1

newborn baby’s brain vs. adult brain- weight and no. of neurones

Answer 1

newborn baby’s brain: ca. 370 g (–> development continues after birth)
adult brain: ca. 1.5 kg (with ca 100 billion neurones)

Question 2

growth rate of the brain

Answer 2

growth rate of a newborn baby’s brain: 1 % per day
–> growth rate slows down to ca. 0.4% per day by the age of 3 months (90 days) –> at 90 days of age the brain’s volume is 64% larger than at birth (cerebellum is the fastest growing region) –> by 5 years of age the brain has reached about 90% of the volume of an adult’s brain

Question 3

connections in an infant’s brained synaptic pruning

Answer 3

in the first 2 years number of connections between neurones increases rapidly (a 2 yo baby has 50% more synapses than an adult brain)–> synapses use a lot of energy–> number of synapses reduced during early childhood and the brain begins to fine tune the connections (synaptic pruning)–> the process is shaped by the baby’s experiences

Question 4

connections in an infant’s brained synaptic pruning

Answer 4

in the first 2 years number of connections between neurones increases rapidly (a 2 yo baby has 50% more synapses than an adult brain)–> synapses use a lot of energy–> number of synapses reduced during early childhood and the brain begins to fine tune the connections (synaptic pruning)–> the process is shaped by the baby’s experiences –> weaker connections diminish while stronger synapses grow and stabilise

Question 5

competitive elimination

Answer 5

heavy synaptic pruning during adolescence with stronger connections beating out weaker ones

Question 6

processes that occur in adolescent brain

Answer 6

competitive elimination (heavy synaptic pruning) and improving remaining connections by extending dendritic branches and myelination of axons especially in frontal lobes.
Increasing in white matter volume esp. in corpus callosum (connecting the brain's right and left hemispheres) that enhance learning capacity (due to increasing connections)
the enhanced connections change reward system and changes the balance between the frontal and limbic regions.

Question 7

plasticity

Answer 7

the ability of the brain to modify itself and adapt to environmental challenges, including sensory inputs.
categorised as experience- expectant (integrating environmental stimuli into normal developmental patterns) or experience dependent (continuing changes in the organisation and specialisation of a person’s brain regions as a result of life experiences that are not universal or anticipated)

Question 8

The adult brain

Answer 8

between childhood and adulthood the brain loses grey matter and increases white matter (strong connections become more myelinated and the brain becomes more “wired” up). At age 40 the white matter reaches its peak volume.

Question 9

cognitive changes in ageing

Answer 9

working memory and declarative memory decreases (autobiographic, episodic memory and learned facts)- while non declarative memory remains intact; selective and divided attention declines with age;

Question 10

volume loss of the brain during ageing

Answer 10

brain volume starts declining at ages 30 to 40 and becomes more rapid at age 60. volume loss isn’t uniform and different areas lose volume at a greater rate than others (PFC, cerebellum and hippocampus show the biggest losses)

Question 11

volume loss in ageing vs. in adolescence

Answer 11

In ageing- volume loss is due to shrinking neurones, decreased complexity of dendrites and reduced myelin,
In adolescence- volume loss is due to synaptic pruning and elimination of excess neurones.

Question 12

last in first out theory

Answer 12

the last brain regions to reach maturity are the first ones to deteriorate (e.g as in cortical thinning that the frontal and temporal lobes, the last regions to fully develop are the first areas to thin out in ageing.

Question 13

chemical changes during ageing

Answer 13

less dopamine is synthesised in older age and reduction of receptors that bind neurotransmitters. some suggest that that serotonin synthesis also decline with age

Question 14

factors that influence brain ageing

Answer 14

• oxidative stress and DNA damage (due to high production of free radicals in metabolic processes and decrease of mechanisms to neutralise them)
• immune dysfunction (microglia become more active and increasing response to inflammatory processes but at the same time damaging anti-inflammatory molecules that are important)
• impaired protein recycling (decrease in the efficiency of breakdown and recycling of damaged protein leads to buildup of damaged molecules in the braincells)