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Pre-Adult Brain Development (Biological) - Coggle Diagram
Pre-Adult Brain Development (Biological)
Brain development
Structures
Structure of brain is hierarchal -> primitive structures develop first, more advanced structures develop later and continue through adolescence
Limbic system:
Develops through childhood and adolescence
Structures including amygdala which connects to the ventral striatum and nucleus accumbens
Processes emotional experiences and regulates emotions
Cerebral cortex:
Thin covering of the brain, where thinking takes place
Divided into number of cortexes
Frontal cortexes controls higher cognitive functions (abstract thinking) and problem solving/decision making
Auditory-visual cortex -> processing of sensory information
Motor cortex -> movement-related information
Extensive development in early years but reaches full maturity in late adolescence
Developmental processes
Synaptogenesis:
Born with all neurons we need, but synapses develop in childhood and beyond
Synaptogenesis is process of new neurons forming
Develop when axons and dendrites grow towards each other to form networks
Contributes to greater complexity of the brain
More synapses = more neurotransmitter activity
Myelination:
Brain growth from birth to two years old grows form 25% to 75% of adult brain size
Myelin is a fatty substance that insulates neurons
Allows conduction of electricity
Synaptic pruning:
Creates organisation in the brain
Period of synaptic loss to fine tune brain structure
Inactive synapses are ones to be pruned
Allows areas to become specialised for certain functions ( e.g. auditory, visual, sensory, motor, etc)
Surviving neurons become myelinated
Risk-taking and the brain
Adolescence is synonymous with risk-taking in the minds of many parents, teachers an politicians (e.g. binge drinking, drug taking, reckless driving, unprotected sex)
Some reality to stereotypes -> e.g. mortality rate and unintentional injuries increase from childhood to adolescence (Western)
Main cause for death/disability in adolescence is preventable (accidents/suicides)
Dual-systems theory:
Steinberg (2008) -> dual-systems theory: risk-taking in adolescence is directed by the interaction of two brain systems that mature at different times
Ventral striatum (VS): emotion-regulating system that matures relatively early in adolescence in response to changes in the ventral striatum
Changes due to increased dopamine
VS includes nucleus accumbens (NA) which is key in brain's reward system -> sensation-seeking/addiction
VS has greater sensitivity in adolescence
Johnston (2006) -> changes in VS matched increase in arrests for criminal behaviour, peaks mid-late adolescence
Peak female 16, male 19
Prefrontal cortex (PFC) -> slower to develop
Cognitive control system directed by PFC, linked with planning, decision-making, response inhibition, goal-directed behaviour, ability to assess risk
Synaptic pruning -> doesn't fully mature until young adulthood
Not able to exert executive control over first system that rewards sensation-seeking behaviours associated with taking risks
Imbalance between systems only during adolescence
Adolescent behaviour more impulsive than child/adulthood
Research study:
Meyer and Bucci (2016) -> lab experiment to mimic system imbalance in rats
Decreased PFC and increased NA
Rats took twice as long as control group to learn to inhibit response to expected reward
Not normal behaviour but matched behaviour of adolescent rats
Barkley-Levenson and Galvan (2014) on the Adolescent brain
Background and aims
Galvan (2013) showed heightened sensitivity to rewards -> linked with increased response of VS when adolescent anticipates or receives or receives expected/unexpected rewards
Unclear if due to genuine phenomenon or extraneous variables -> use of money as a reward -> people value money more than others
Barkley-Levenson and Galvan defined subjective value (SV) as 'the value that an individual places on a stimulus'
Batra (2013) -> ventromedial prefrontal cortex (PFC) and VS together form brain's valuation system
How brain represents SV measured by expected value (EV). Defined as 'sum of all the possible outcomes of a choice multiplied by their probabilities'
Aims:
Adolescents would be more sensitive than adults to increased EV
Adolescents would show greater VS activation as EV increased, compared to adults
Adolescents would still show a heightened VS response even after matching with adults on number of gambles accepted
Method
Lab-based quasi experiment. IV was whether participant was adult/adolescent. DV were number of gambles in a 'spinner' game accepted by participant and activity in ventral striatum of brain
Sample:
19 adults 25-30 yrs (8m, 11f) and 22 adolescents 13-17 yrs (11m, 11f). All right-handed
Self-selected -> advertised posters/online
Used previous UCLA participants
All healthy
Apparatus:
fMRI scans using a 3-Tesla Trio MRI machine
140 functional, 2 structural images taken per p
Procedure
Intake session:
Adult ps gave informed consent, under 18s -> parents gave informed consent
Ps given details of monthly allowance and where it came from
Average for adults $467.11, average for adolescents $52.50
End of session, each given $20 as playing money -> chance to double or nothing (gave effect of ownership)
Each participant visited the lab on two occasions for an intake session and again one week later for fMRI
fMRI session:
Gambling task -> spinner
Ps shown on-screen spinner split in two between $5 and $20. One value gain, other lose
Gain and loss countered for ps
Trials: 192 per p. 24 runs had only gain, 24 would be loss, 48 mixed trials -> would show risk-taking behaviour
EV mixed value: -$7.50 - +$7.50
EV gain only: +$6 - +$19
EV loss only: -$6 - -$19
Task was to decide on which trial whether or not they were prepared to gamble their money
Money added or removed at end of run for participation
Ps trained in task before scan
Results
First hypothesis:
Increasing EV made acceptance of gamble more likely. Greater in adolescents
Disposable income had no effect on link with EV and gamble acceptance
Researchers analysed gain-only and loss-only trials -> not risky because ps knew outcomes
Gamble acceptance didn't change for adults or adolescents
Adolescents behave as adults when no risk involved
Second hypothesis:
fMRI scans showed as EV increased, increased activation in superior medial PFC
Decreased activation accompanying increased EV in other brain areas such as amygdala and hippocampus
Adolescents show greater activation to increased EV in left VS than adults
Third hypothesis:
Researchers matched two groups on acceptance behaviour by analysing data from ps with high gambling acceptance (>80%) on high EV trials
Found that difference remained
Conclusions
Adolescent brain uniquely heightened sensitivity to rewards
Valuation system in medial PFC and adjacent areas
VS important in valuation in adolescents
Hyperactivation of VS in adolescents
Strategies to reduce risk-taking behaviour using knowledge of brain development
Nurse visitation programmes (NVP)
Severe stress early in life can increase likelihood of risk-taking behaviour in adolescence
Early stressful experiences can disrupt synaptogenesis/synaptic pruning
Associated hormones can damage prefrontal cortex, limiting influence on VS
Nurse visitation programme (NVP) targets men/women expecting a baby and high risk of mistreating it
Reducing stress
Usefulness:
Preventing mistreatment of child is beneficial, avoids risk of damaging brain structure and processes (e.g. synaptogenesis)
Intervention encourages parents to provide better nurturing care for child
Care continues into adolescence and breaks links with development of impulsivity and ultimately risk-taking behaviours
Effectiveness:
Izzo (2005) structured interview with mothers 15 years after NVP. Able to cope better than mothers not on NVP
Interviewed children -> ran away from home less, were arrested less often, had fewer sexual partners, smoked less, had fewer alcohol/drug related behavioural problems
No effect on suspensions from school, disruption in school, 'major delinquent acts'
Practicalities:
Results included mothers that has pre-birth visit but none else, later outcomes not as positive than ps with full interaction
Graduated driver programmes
Graduated driver programmes (GDP) commonly used in US to reduce incidence in inexperienced driver's first 1000 miles
Driving and the pre-adult brain:
Delay of maturation of brain governed by VS results in underdevelopment of cognitive skills crucial to driving
Reducing the impact of arousal:
High arousal caused by driving and with friends
Together can be toxic, interventions devised to prevent combination occurring or reducing impact on behaviour
Stages of GDP:
Lower stages -> lower speeds limits, restriction of hands-free mobiles
3 stages -> learner (always supervised), intermediate (only supervised in dark), full privileges (after 18)
Usefulness:
Useful restrictions -> limited passengers, friends only allowed in stage 2 with adult present
Effectiveness:
Dee (2005) -> GDPs reduced 15-17 years fatalities by 5.6%
Romano (2011) -> GDPs reduced speeding-related fatalities in white, African-American and Asian adolescents. Didn't affect Hispanics
Risky driving could relate to social and cultural reasons as well as brain development
Practicalities:
Pedan (2008) -> most significant element is extended period of supervision in first stage
Longer it takes for adolescent to drive unsupervised, less risky driving behaviour
Evaluation
Nature/nurture
Nature:
Brain development
Synaptic pruning
Nature because natural process that occurs during childhood
Nurture:
Freewill/Determinism
Freewill:
Barkley-Levenson and Galvan
Risk taking behaviour -> choice to behave this way
Freewill as individual chooses to act this way
Determinism:
Developmental processes
Synaptic pruning -> prunes inactive synapses and creates organisation in the brain
Deterministic because this will happen regardless of any other factors -> biological
Reductionism/holism
Reductionism:
BL and G
Risk is due to activation in ventral striatum -> heightened in adolescents
Reductionist because it reduces risk-taking behaviours to one factors
Holism:
Individual/situational
Individual:
Risk taking and the brain
Steinberg (2008) -> dual-systems theory: adolescent risk taking directed by interaction of VS and PFC
Individual as this will differ the amount of risk taking behaviour in each adolescent
Situational:
Usefulness
Useful:
Not useful:
Ethical considerations
Not ethical:
BL and G
Gambling task during fMRI scans in second session
Not ethical as may promote gambling in real life
Ethical:
Conducting socially sensitive research
Socially sensitive:
Not socially sensitive:
Psychology as a science
Scientific:
BL and G
fMRI scanner has set protocol, all ps given identical gambling task
Scientific as fMRI protocol is replicable and standardised
Not scientific:
Ethnocentrism
Ethnocentric:
BL and G
Adolescence seen as individual gaining independence
Ethnocentric as the western view of adolescence used (individualist), collectivist cultures may differ results
Not ethnocentric:
Validity
Valid:
BL and G
Internal validity -> made participants believe they earned $20 during intake session
Valid as reduces 'house money effect' so researchers reduced extraneous variables
Not valid:
BL and G
Ecological validity -> gambling task
Lack validity as it resembles few risks take by adolescents and adults in real life
Reliability
Reliable:
BL and G
fMRI scanner followed established protocol so was conducted and analysed
Reliable as established protocol is standardised so makes it replicable -> external
Not reliable:
-
Sampling bias
Bias:
BL and G
Self-selected sampling using posters and online adverts
Biased as may only include certain characteristics -> people who take risks may be more likely to risk signing up
No bias:
BL and G
Equal male/female ratios in both adult and adolescent participants
No bias as reduces gender as extraneous variable