Introduction to the Brain

In order to understand the impacts of trauma on the brain we first need to understand how a normal brain develops. 

A. The brain develops sequentially from the bottom up.  

The first structures of the brain to develop form the foundation for the next structures to grow.  The brain continues to develop with each successive part responsible for more complex functions (e.g. starts with movement, then feeling, then identifying emotions, then ability for abstract thought and self-control).  The order is outlined below, explaining the development and role of each structure.

1. Brain Stem

Things to know

  • Sensitive developmental period pre-birth (in utero) to 8 months and therefore the most developed part of the brain at birth
  • These structures are least capable of change


  • Responsible for basic life functions, i.e. survival
  • Responsible for heart-beat, breathing, sucking, temperature control, blood pressure, regulates sleep cycle

2. Cerebellum

Things to know

  • Sensitive developmental period from 0-24 months
  • Cauliflower shaped structure located just above but behind the brainstem


  • Responsible for movement and interpreting physical and sensory stimulation
  • Helps us to know where our body is in space
  • Helps us with our posture, balance and muscle tone
  • Helps us not to fall over and to control our movements

3. The Limbic System including the Amygdala, Hippocampus and the Diencephalon

Limbic Lobe (in general)

  • Sensitive developmental period 1-4 years
  • Helps us attach an emotion to a thought or memory
  • Is particularly involved with the emotions of fear and anger

Diencephalon (comprises of the Thalamus and the Hypothalamus)

  • Sensitive developing period from birth-12 months

The Thalamus

  • Referred to as the ‘sending and sorting’ part of the brain
  • Receives information from within the body and from the external environment and relays it to pertinent parts of the brain and body
  • Interprets sensations of sound, smell, taste, pain, pleasure, temperature and touch
  • Regulates some emotions and memory

The Hypothalamus

  • Uses hormones to send information to the body
  • Hormones signal the body with what it needs in terms of: heartbeat, digestion, sleep and circadian rhythms, and regulates the endocrine system
  • Links the nervous system to the endocrine system via the pituitary gland
  • Interprets hunger and thirst
  • Helps regulate anger and aggression
  • Has a lot to do when our survival mode is under threat
  • Links with survival related responses such as flight, fright and freeze


  • Mature at birth
  • Associated with the perception of threat
  • Responsible for arousal that is necessary to respond to threat and/or perception of threat
  • Quickly recruits many areas of the brain to deal with threat and of the body to deal with danger
  • Often referred to as the ‘smoke detector’ of the brain as it is highly responsive to sights and smells
  • Impacts autonomic responses in the body and also stores implicit memory


  • Mature between 2-3 years
  • Associated with memory
  • Often referred to as the ‘memory puzzle sorting centre’ as it provides a context to memories and embeds them in our long term memory

4. The Cortex or Cerebrum

Cerebral Cortex

  • Developmental period is birth to 25 years, develops significantly between the ages of 2-6 years and continues to develop as it is stimulated with ‘learnings’
  • The largest part of the brain which includes the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.
  • Associated with higher order thinking and action
  • Plays a key role in memory, attention, perceptual awareness, thought, language and consciousness
  • Related to reasoning, judging, showing logic and contributes to voluntary movement
  • If the brain was an orchestra, the cortex would be the conductor

Pre-frontal cortex

  • Final part of the brain to finish sensitive development
  • It is part of the cerebral cortex which covers the front part of the frontal lobe
  • Maturing in a person’s mid 20’s
  • Responsible for higher order, executive functions such as: foresight and anticipation, focusing and sustaining attention, planning, prioritising and organising, decision making, reflecting, enthusiasm, motivation and persistence
  • Relevant to motor activity and connects the brain’s motor, perceptual and limbic regions

B. The brain also develops laterally

The right and left hemispheres of the brain are each responsible for different functions and develop at different speeds.


  • Holistic, convergent and able to see the ‘big picture’
  • Stores and processes emotions, feelings, creativity and intuition


  • Linear, divergent and focuses on one thing at a time
  • Deals with more logical experiences and challenges, such as language and mathematics

The hemispheres develop at different times and speeds over the years.  The right hemisphere is developing at a greater speed to two years of age.  After two, the left hemisphere takes over.  This intensity of development then oscillates between the two every two years until about 8 years old when they start to integrate with each other.

Watch this video for detailed information on the brain structure.

Integration is Key

Integration is the key to well-being and occurs vertically and laterally within the brain.  The brain develops through the creation of neural pathways which connect different regions of the brain together. 

Neuronal connections are strengthened best when an individual repeats an experience over and over.  If the experience is not repeated, the connection will disappear.  To master a motor activity for example, a child is required to repeat and repeat a running motion and in the practice of it, becomes more precise and faster.  Similarly when playing a musical instrument, learning timetables, singing a song, reading or dancing.  These neural pathways in the brain enable each individual to efficiently interpret the world, their reactions to it and prompt relevant responses.  The brain establishes these pathways as templates to be able to quickly compare a new situation with memories previously stored and ultimately interpret the next steps or actions that will be taken.

Integration of neuronal networks shapes the thoughts, feelings and actions of children and young people.  The greater the number of pathways, the more the functions of the brain become integrated.


  • Enables individuals to apply words to feelings
  • Threads together the experiences that build the memory routines required to ride a bike
  • Combines the experiences of interpersonal exchanges over time that equates to the experience and feeling of trust
  • Uses rehearsal to know how to act in a peer group, how to remember the six times tables and whether or not to be frightened of snakes

Integration and Trauma

Greater integration results in children being more adaptive and flexible.  When integration is blocked or put under pressure by stress and trauma, the children’s inner world and capacities to adapt to the needs and challenges of their physical and relational environment is significantly hampered.  Rather than supporting learning, connection and other developmental goals, the child’s neuronal connections have formed to support survival in a stressful caregiving environment. 

Experiences of trauma can also mean that hemispheric activation is kept separate and there is reduced opportunity for hemispheric integration.  In this case the "RH is seeing the whole collage but is trapped in the present (feels like the trauma is still happening) while the LH is unable to pick out details and put meaning to what is happening” (Australian Childhood Foundation).

As such, the goal of any support plan for children and young people is to promote integration at a neurobiological and interpersonal level.
Further Resources