adolescent brain

Tamnes et al. (2017) - Brain Matter Volume

- Looked at thousands of participants & the amount of white & grey matter
- White matter increases with age while grey matter decreases
- Adolescents have increasing white matter for better cognitive functioning

Adolescent Recklessness

- Adolescents take more risks than any other age group
- Puberty coincides with increased reward-seeking through a remodelling of the brain's dopaminergic system
- Declines in adulthood due to better cognitive control & self-regulation
- Public education programs aren't very effective suggesting that it's not a matter of not knowing how to behave

Adolescent Recklessness - Dopaminergic System

- Everything involved in the dopamine reward system
- Made up of the amygdala, nucleus accumbens, orbitofrontal cortex, medial prefrontal cortex, & superior temporal sulcus
- Responsible for social information processing (recognition of social stimuli/judgments/reasoning)

Dopaminergic System - Receptor Density & Activity

- Decreases start around 10 years old in the striatum (basal ganglia) & prefrontal cortex
- Activity in prefrontal cortex increases in early adolescence

Steinberg et al (2008) - Sensation Seeking & Impulsivity

- Had a diverse sample of 935 people aged 10-30
- Looked at self-reports on sensation seeking & impulsivity
- Also used behavioural measures that looked at planning/executive functioning & risk taking

Tower of London: (move balls on pegs to match the “goal” in as few moves as possible)

• Measures how long participants wait before making first move (more waiting = better planning = less impulsivity)

Stoplight: Driving simulation game trying to arrive in less than 2 mins. Break at yellow light must wait 3 secs (low risk & high reward). If you run red light, car crashes and you lose 6 secs (high risk & payoff)

• Measures how often participants take the risky choice

Steinberg et al (2008) - Sensation Seeking & Impulsivity Self-Report Findings

Impulsivity decreases with age & sensation-seeking seems to peak at 12-15 years old

Steinberg et al (2008) - Sensation Seeking & Impulsivity Behavioural Findings

- Older participants take longer to make their first move in the task than younger participants
- Younger participants don't change their behaviour as things get harder in the planning task
- Younger participants were more reckless than older participants in the risk-taking task - highest in teens especially in peer contexts

Steinberg et al (2008) - Sensation Seeking & Impulsivity Implications

- Adolescents & adults differ behaviourally (including in self-reports) in a way that's consistent with brain differences observed in reward circuitry
- Brain areas implicated in self-regulation take longer to mature which is consistent with the heightened sensation seeking in adolescence as better impulse control develops in adulthood

Casey, Getz, & Galvan (2008) - Adolescent Recklessness

- Subcortical limbic regions mature faster than the prefrontal cortex

• why teens feel a strong reward drive

• why teens are aware of risks,know whats safe yet still takes risks because the reward feels stronger

- Functional connectivity between regions with development & experience provides a mechanism for controlling drives
- Risk-taking involves subcortical systems known to evaluate rewards

Maturing During Adolescence

The same areas that show the largest change from childhood to adolescence were different when comparing adolescents to young adults

Maturing During Adolescence - Specific Differences

- There was little change in parietal, temporal, & occipital lobes
- There were large group differences in dorsal, medial, & lateral regions of frontal lobes
- There were some changes in subcortical regions that could be related to motor functions mediated by the frontal cortex

Galvan et al. (1999) - Reward & Nucleus Accumbens

- Looked at 37 participants aged 7-29
- There were 3 cues associated with different reward values
- Participants had to press with either their left or right finger depending on which cue appeared as quickly as possible
- Rewards were received if correct but none were given if they were incorrect
- Participants received $50 for participation & could earn up to $25 more through performance

Galvan et al. (1999) - Reward & Nucleus Accumbens Findings

- Larger rewards produce more neural responses for largest reward condition
- Adolescents showed more change than children & adults in nucleus accumbens for largest reward condition
- Children showed the greatest change in the orbitofrontal cortex
- Adults showed more learning across trials
- Amount of learning increased with age

Galvan et al. (1999) - Reward & Nucleus Accumbens Implications

Adolescents differ from children & adults in the extent to which rewards impact activity in the nucleus accumbens & orbitofrontal cortex

Why are adolescents more prone to risk-taking, based on NAc and OFC development?

• NAc: matures early → hypersensitive to rewards.

• OFC: matures later → weak impulse control.

• Result: Rewards have a bigger impact on adolescent decision-making.

OFC Development across ages

Adolescents —> Weak OFC activity (still developing)

Adults —> Stable, consistent OFC activity (better impulse control) 

OFC responsible for impulse control

Galvan et al. (1999) – Reward, Learning & Reaction Time

• Adults (mature OFC) → showed the most learning across trials (faster, more strategic).

• Adolescents → showed some learning, especially for large rewards, but less consistent (immature OFC).

• Children → showed no learning, reaction times stayed variable.

Media Use & Brain Development

- Adolescents are highly sensitive to acceptance & rejection through social media
- Heightened emotional sensitivity & protractive development of frontal areas makes them reactive to emotion-arousing media
- Adolescents are more aggressive after being rejected online

Van Der Meulen et al. (2017) - Brain Activation & Peer Feedback

-Used fMRI to test media imagery & peer feedback on neural activity in 24 female adolescents
- Participants had to rate the sizes of bikini models as either too thin or normal before viewing peer feedback
- Looked at activity in the trials where participant says too thin and the peer says normal to the trials where peers agreed

Van Der Meulen et al. (2017) - Brain Activation & Peer Feedback Findings

- Peer disagreement showed more activity in the insula (emotion, self-awareness, cognitive functioning) - social conflict
- This wasn't the case for when participant says normal & the participant says too thin
- There was also increased activity when the participant had lower self-esteem

• The lower the girls self esteem the more her brain lit up when peers disagreed with her (sensitive to peer rejection)

• Girls with higher self esteem were less affected by peer disagreement (weaker brain response)