Pre- adult brain develepment.

• 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, but 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

  
• 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
• Adolescent brain development


  Has significant impact on decision making and behaviour, paired with major life events and environmental changes
• 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
• 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
• 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
• 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

  
• 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
• Barkley-Levenson and Galvan (2014) study


  1. Asked adults and adolescents to volunteer

  2. Session 1: Asked questions about income to control for risk perceptions, gave $20 gambling money

  3. Session 2: Came back a week later, had fMRI scan whilst gambling on spinners, could win/lose money
• Synaptogenesis


  The process of forming synaptic connections between neurons
• Risk-taking behaviour


  Defined as gambling behaviour (high risk = 50/50 gambles, low-risk = win/win and lose/lose gambles), increased risk = higher Expected Value
• Myelination


  The process of forming a myelin sheath around the axons of neurons
• Participants may not have subjectively felt the situation was risky, e.g. gambling with someone else's money, $20 not a huge amount
• Results of Barkley-Levenson and Galvan (2014) study


  • No significant differences in adults and adolescents for trials with no risk
  • Adolescents accepted more gambles with increased expected value than adults
  • In both groups, as expected value increased, activity increased in medial prefrontal cortex, decreased in amygdala
  • Adolescents had more activity in left ventral striatum, which increased greatly as expected value increased compared to adults
• Synaptic pruning


  The process of eliminating unused synaptic connections in the brain
• This study supports Psychology being a science, as conditions were highly controlled and standardised, and objective measures like fMRI were used
• This study suggests that the development (or lack of) in the teenage brain ultimately causes the risky decisions made by adolescents, rather than these risky decisions being made by choice

  
• Timeline of brain development

  1. Newborn

  2. Infancy/childhood

  3. Adolescence
• WIN $8


  Potential gain from gamble
• LOSE $15


  Potential loss from gamble
• At the time of birth much of the spinal cord and brain stem are well-developed, however, upper regions such as the limbic system and the cerebral cortex are still immature
• WIN $15


  Potential gain from gamble
• Had to decide whether to 'accept' or 'reject' the gamble


  Participants made a choice
• All the neurons in the cortex are produced while the baby is in the uterus but they remain poorly connected until after birth
• For both groups, increasing Expected Value

  Increased the likelihood of accepting a gamble
• A huge number of synaptic connections (synaptogenesis) are made during the first few years in the cerebral cortex, signalling the development of conscious actions, memories, thoughts and emotions
• The influence of increasing Expected Value on response

  Was greater for adolescents versus adults
• This study supports Psychology being a science, because conditions were highly controlled and standardised in a laboratory
• Synaptic production goes into overdrive during childhood, starting earliest in the visual cortex and eventually in the frontal and temporal lobes
• Strength of the research

  • Highly replicable, so the reliability of the findings with other groups of adolescents could be tested
• Grey matter which contains synaptic connections reaches peak volume and begins to decrease in density across several cortical regions in adolescence (ages 13-19)