Adolescent brain

Adolescent brain

1. Onset of puberty - independence - impulsive and risky decisions. Brain develops up to 25. develops bottom up back to front.

   • Fully mature subcortical regions take control from developing PFC - impulsive and emotional
   • Less influence of PFC compared to accumbens and amygdala, in reward valuation and emotional reactivity. Increase in nucleus accumbens immediately before making a risky decision

2. The reward circuit

   • Information travels to the PFC - brain responds by releasing dopamine - reward system - main dopamine pathways in the brain
   • PFC - needs to be fully developed to make appropriate decisions: INvolved in cog planning and decision making
   • Subcortical regions
     • Septum
     • Ventral tegmental area: Part of midbrain - produces dopamine and forms 1/4 major dopamine pathways
     • Amygdala - reward sensitive dopamine system - memory consolidation for emotionally arousing events
     • nucleus accumbens (ventral striatum) - small region of forebrain helps regulate survival

3. Galvan et al. 2006 Risk in the adolescent brain

   • Different cues had different reward Pirates and coins. When you see different cue had to remember where it was.More risk, more you engage nucleus accumbens

4. Triadic brain (Ernst pine and harding)

   • PFC, Ventral striatum, amygdala. All interconnected. Adults have no link between ventral striatum and amygdala, other two connections are weak.
   • PFC - control centre - tells you if something is risky, amygdala - avoidance of harm, ventral striatum - makes you excited
   • Mature brain is balanced, teenage brain is biased towards reward, weaker control and weaker avoidance.

5. Inhibition in the adult brain - Somerville et al. (2011) Social cues of positive and neutral faces, when see neutral face click go when happy inhibit a response. Teenagers more likely to do false alarms. Same area of brain lit up as Galvan.

6. Brain development - Casey (2008) - imbalance between limbic system and PFC. In children PFC and nucleus accumbens arent fully mature. Imbalance in teens explains behaviour.

7. Risk and Reward in the adolescent brain (Van leijenhorst 2010). Probability of a high risk gamble 33% low risk gamble 66% - Used fMRI paradigm. Tested 10 - 23 yo. Decision making and reward anticipation.

   • high risk taking was seen across the age ranges, no behavioural difference in risk taking in lab conditions. Region of brain associated with reward - cordate part of ventral striatum. Peak activation in adolescence when see high risk gamble. Choosing high risk over low risk - medial PFCactivation. Choosing low risk over high risk - dorsal lateral PFC (last to mature, controls incentive)
     • linear decrease in activation of dorsal ACC when choosing high risk - younger you are, the more likely you are to use this part.
     • Supports CASEY about the imbalance

8. Dreyfuss et al. (2014) fearful instead of happy faces. Taps into threat to see why teenagers commit more crime. Go when see neutral don't go when see negative. Impulsivity linked to reward (happy)

   • non-linear pattern peaked in the teenage response. Cant control impulsivity. teen specific brain patterns. Children too underdeveloped to react. Adolescent emergent used same areas of the brain.
   • Medial PFC and Occipital PFC - activated- avoidance of harm. more activated in teenage brain. Dependent on brain regions see different patterns.

9. gender difference - male react more to fearful faces, females activate avoidance mechanism more.

10. Triadic brain - too simple- more areas are involved, caseys model - not just limbic structure, some cortical regions.

    • circuit based approach CASEY - regions interconnected that develop. all about connectivity which changes from childhood to adulthood. Hierachal changes from subcortico - subcortical to cortico - subcortical

11. Albert et al. 2013 - teens are more likely to make risky decision when around peers than adults and young adults. increase 60% - big difference in activation in ventral striatum and orbitofrontal cortex compared to being alone.