pre-adult brain development

• Brain development refers to how the neurons in the brain make connections and become more efficient in communication, and how this affects behaviour
• Majority of brain development occurs in first 3 years of life, mainly in the first 3 months
• Grey matter


  Nerve cell bodies that make up about 40% of the adult brain, processes information and is involved in higher order thinking skills
• Prefrontal cortex


  Cognitive control system which is linked to planning, decision making and ability to assess risk
• Casey's study


  • Inferior frontal gyrus (associated with response inhibition, low delayers had reduced activity)
  • Ventral striatum (associated with rewards, low delayers had greater activity)
• Brain is fully developed around mid-20s
• Brain development


  1. Born with 100 billion neurons, poorly connected at birth

  2. Synaptogenesis - synaptic connections made in hind part of brain

  3. Brain develops back-to-front

  4. 3 year old has twice as many synaptic connections as adult

  5. Exuberant synaptogenesis

  6. Synaptic pruning begins

  7. Synaptic pruning continues

  8. Pre-frontal cortex is last to mature

  9. Adolescents get better at abstract reasoning

  10. Neurons that survive pruning become myelinated
• Whole process of overproduction, synaptogenesis, pruning and myelination occurs at different rates in different brain areas
• Development of adolescent brain, along with hormonal changes, have significant impact on decision making and behaviour
• Pre-frontal cortex


  • Linked to response inhibition, impulse control, lower activity associated with more risk-taking behaviours
• Ventral striatum


  • Reward centre, increased activity associated with rewards
• Adriana Galvan's TED Talk discusses how brain development affects teenage behaviour, particularly why risk-taking may be necessary in adolescents and the areas of the teenage brain she has investigated
• Barkley-Levenson and Galvan (2014) study


  1. Asked adults and adolescents to volunteer

  2. Session 1: Asked questions about income, gave $20 gambling money

  3. Session 2: Gambling task in fMRI scanner, 192 gambles (144 50/50, 24 win/win, 24 lose/lose), had to decide to accept or reject gamble
• Risk-taking behaviour


  Gambling behaviour, increased risk defined as gambles with higher Expected Value
• Participants may not have actually felt the situation was risky, as they were gambling with someone else's money and $20 is not a huge amount
• Results of Barkley-Levenson and Galvan (2014) study


  • No differences in adults and adolescents for no-risk trials
  • Adolescents accepted more gambles with increased Expected Value
  • Both groups: Increased Expected Value increased activity in medial prefrontal cortex, decreased activity in amygdala
  • Adolescents: More activity in left ventral striatum as Expected Value increased, compared to adults
• This study supports Psychology being a science, as conditions were highly controlled and standardised, and objective measures like fMRI were used
• Study suggests risky decisions by adolescents are caused by brain development, rather than being a choice
• WIN $8


  Potential gain from gamble
• LOSE $15


  Potential loss from gamble
• WIN $15


  Potential gain from gamble
• Brain development


  Development of the structures in the brain, and also the development of its functions

  
• Brain development


  • The primitive structures essential for survival develop first and most quickly in the first few months of life
  • The more advanced areas, towards the front of the brain, take longer and continue to develop into adolescence
• Grey matter


  Made up of nerve cell bodies and makes up about 40% of the adult brain, it processes information and is involved in high order thinking skills
• White matter


  Made up of neurons with long axons that carry messages to and from grey matter areas, and between the grey matter and that other parts of the body
• Myelin


  A fatty white substance that surrounds the axon of some nerve cells, forming an electrical insulating layer. Myelin enables nerve cells to transmit information faster and allows for more complex brain processes
• Synaptogenesis


  The process of forming synaptic connections between neurons
• Myelination


  The process of forming a myelin sheath around the axons of neurons
• Synaptic pruning


  The process of eliminating unused synaptic connections in the brain
• Timeline of brain development


  1. Newborn

  2. Infancy/childhood

  3. Adolescence
• Early brain development


  • At birth, the spinal cord and brain stem are well-developed, but the limbic system and cerebral cortex are still immature
  • Synaptic connections (synaptogenesis) develop rapidly in the first few years, especially in the visual cortex, frontal and temporal lobes
• Adolescent brain development


  • Grey matter reaches peak volume and begins to decrease in density across several cortical regions (synaptic pruning)
  • The prefrontal cortex is one of the last areas to mature, continuing into the early 20s
• Ventral striatum


  A key component in the brain's reward system, involved with attention-seeking behaviour and addiction. It responds to new experiences and has greater sensitivity to rewards in adolescence
• Prefrontal cortex


  A cognitive control system linked with planning, decision-making, response inhibition, goal-directed behaviour and risk assessment. It develops later, not fully maturing until the early to mid-20s
• Adolescents are more prone to risk taking and impulsivity than any other age group
• The limbic system develops earlier than the prefrontal cortex


  This makes risky decisions more common and more likely to occur under higher levels of social influence in adolescence
• The aim was to look at whether there is an identifiable difference in neural activity between adolescent and adult brains when given risk taking scenarios such as gambling, with different expected values for the outcome of the gambles
• The sample consisted of 19 healthy, right-handed adults (ages 25-30) and 22 healthy, right-handed adolescents (ages 13-17)
• Procedure of Barkley-Levenson & Galván (2014)


  1. Intake session: Participants completed information on income and spending money

  2. fMRI session: Participants underwent an fMRI scan while undertaking a decision-making 'spinner' game with 192 trials, 144 of which had a gain on one side
• Participants


  Given $20 to use as 'playing money' in the next session, could gamble and win up to another $20 or lose up to $20