Adolescent brain

• White matter


  Neural connections between brain areas and is myelinated - cell bodies are mostly in the gray matter but the long axon coated in myelin sheath is white matter (has layers of fat which helps to speed up signal and appears white on MRI)
• fMRI


  Using fMRI we can get an impression of the activity in the brain
• MRI


  Provides info on the structure of the brain
• fMRI


  Provides info on function of different brain areas
• fMRI


  Scans the brain in slices which then gets put together afterwards
• fMRI


  Not a direct measure of brain activity, it actually measures changes blood flow meaning the amount hemoglobin (oxygen) in red blood cells - more oxygen = more activity
• EEG


  Has high temporal resolution but low spatial resolution (more of a direct measurement of the brain signals)
• fMRI


  Has high spatial resolution (mm) and low temporal resolution
• fMRI


  Non-invasive technique
• EEG


  Require you to wash your hair after the experiment
• Important things to consider when using fMRI research techniques

  • BOLD signal is not an absolute measure of brain activity but relative
  • Because it not absolute, a control condition is crucial
  • You need many trials per condition (more than 20)
  • Fixation is needed between trials (e.g black screen with white plus)
  • Have to engage participants
• Adolescence


  Starts with the onset of puberty - Time in between being a child and an adult
• Structural brain development


  • There is a massive increase in gray matter from birth to 8 yrs old - indicates neural connections explode after birth meaning more neurons connect with other neurons
  • After the age of 11, gray matter decreases whilst white matter increases
  • If the connections are not used, they are lost - use it or lose it
  • Visual regions develop early - front and temporal regions develop late
• Nelson et al. (2005) Neuroscience models for understanding adolescence development

  • Understanding the dramatic changes in social behavior in adolescence (social re-orientation)
  • Social information processing network (SIPN) - consists or 3 main parts all working together
• 3 main parts of the Social Information Processing Network (SIPN)

  • Detection node (perceptual processing)
  • Affective node (emotional processing)
  • Cognitive-regulation node (regulation and monitoring of perception and affection)
• Detection node


  Processes questions like: is this a social stimulus, is it a living being, what kind of being? Who is this?
• Affective node


  Processes questions like: Should I approach or avoid?
• Cognitive-regulation node


  Processes questions like: What are their intentions (ToM), How should i respond?
• The three nodes in the SIPN model have different developmental trajectories which may explain adolescent behavior
• Adolescent development of the SIPN nodes

  • Detection node - Early maturation (matures/develops early)
  • Affective nodes - Maturation in early adolescence, Hypersensitive and overactive in early adolescents
  • Cognitive nodes - Maturation in late adolescence
• Affective node


  Functional and anatomical reorganization during puberty, Gonadal hormones (e.g estradiol, testosterone) are related to how affective node structures respond to social stimuli, Heightened emotional responsiveness to affective stimuli, especially in particular contexts (e.g the peer context)
• Cognitive node


  Maturation in late adolescence, Prefrontal cortex (including OFC, VLPRC, DLPFC, mPFC) do not reach maturity until early adulthood, Performance on inhibitory tasks improves until late adolescence, This development is independent of hormonal status (and is related to myelination and pruning)
• Dual system model / imbalance model

  • Affective nodes (limbic regions) - heightened activity and developments -> perceive rewarding stimuli as more rewarding
  • Prefrontal - lacking/delayed development -> more risky behavior
• Role of motivation


  Recent evidence does not support a simple model of frontal cortical immaturity, Growing evidence for importance of social-affective processing (e.g role of motivation salience of the context e.g task instructions, strategies. Affective appraisal of task performance, peer pressure), Motivation (social/contextual) can modulate cognitive control (e.g rewards can improve performance) - Motivation can enhance cognitive control to an extent, Control can suffer when required to suppress action towards rewards
• Rewards can improve performance


  Monetary reward had much larger effect on adolescents but didn't really have an effect on performance for adults - indicates effect of motivation
• In this experiment adolescents show higher ventral striatum activation and higher prefrontal cortex activation
• Social cognition


  A (uniquely) human trait is the ability to understand each other as conscious beings with internal mental states
• Cognitive processes required to understand and interact with others

  Recognizing, understanding and interpreting social cues from others, including mental states, Using this knowledge to guide interactions, This includes understanding that your state of mind differs from others (ToM)
• Social brain


  Network of brain regions that underlie these social cognitive processes, including the dorsomedial prefrontal cortex, precuneus, posterior superior temporal sulcus, temporo-parietal junction, anterior temporal cortex
• Mentalizing


  Refers to understanding another's perspective that is not your own
• Structural development for mentalizing

  Gray matter volume and cortical thickening in pSTS, TPJ and dmPFC decreases from childhood into the early 20s, Faster cortical thinning of mPFC predicted a stronger increase in friendship quality across adolescents, Faster maturation (particularly of the medial prefrontal cortex) showed better and higher friendship qualities
• Functional development for mentalizing

  Temporal/posterior regions become more active but more efficient, Anterior rostral PFC more active in adolescents than adults suggesting adolescents need to put more effort into understanding others mentalizing
• Recruitment of brain regions during mentalizing

  Adolescents use cognitive strategies that rely more on explicit reflection about the self and others, subserved by the dmPFC, Adults rely more on the automatic processing of social subserves by the temporal lobes, Maturing inhibitory control might contribute to these changes - better able to inhibit initial response thinking about yourself and instead thinking about other intentions
• Fairness Game


  One person who decides for everyone and other person has to accept, Allocator gets 10 Euros and there are 3 options for how they can divide it, Size of donation increases with age e.g young children keep more to themselves
• Ultimatum Game


  Similar but the receiver decides whether to accept the offer or not. If they don't accept the offer then no one gets anything, Younger children have similar actions in both games indicating that they are mainly thinking about themselves, Older children use a different strategy in the ultimatum game indicating that they have more understanding of how the other person will feel and the other's perspective
• Stop signal reaction time task (SSRT)

  The shorter the SSRT means participants are better at inhibitory control (young children are not very good at this), Children who perform well on the SSRT is related to better strategic behavior - inhibitory control is important for the development of being able to mentalise
• Better strategic behavior and better performance on the SSRT

  Related to an increase and heightened activity in the DLPFC
• Responder in Ultimatum Game


  Game theory suggest responders accept every offer greater than zero, However, in reality responders usually reject offers smaller than 20% of the stake
• Mini-ultimatum game


  Age related increase in perspective taking, Young children will more often reject an unfair offer even though there is no alternative condition meaning they do not take into account the other perspective, they just see an unfair offer and say no, In the no alternative condition, as age increases, there is increased understanding that the other person had no option and therefore, they become likely to accept the offer
• Age related increase in TPJ and DLPFC activity

  Related to increasing perspective taking (intentionality consideration and strategic behavior) and impulse control skills