The brain is made up of two halves or hemispheres, joined by the corpus callosum and more minorly by the anterior and posterior commisures. Communication between the two hemispheres and flexibility of function and use of both hemispheres is vital for healthy brain, body and emotional function. Clinically when we observe patients with an imbalance in the maturity and function of the left and right hemispheres we can see a range of symptoms and signs.
LEFT side functions: The gas pedal of our brain:
Small muscle (fine motor) control
Light touch processing
High frequency sound processing
Word reading (phonics and decoding)
Math calculations (arithmetic)
Picks out the details of situations
Picks out details of people
Likes the same task, situation over and over again
Turns on the immune system
Linear, logical thinking
IQ (Intelligence Quotient)
RIGHT side functions: The brake pedal of our brain:
Negative emotion control
Gross motor, core muscle control
Deep touch processing
Low frequency sound processing
Understands the "big picture"
Has intuition with people
Likes new tasks or situations
Turns off the immune system
Creative side of thinking
EQ (Emotional Quotient)
A lack of LEFT-brain function can be associated with:
Poor fine motor control: drawing, hand writing, detailed tasking
A lack of RIGHT brain function can be associated with:
Mood instability (highs and lows)
Inability to focus in school
Poor muscle tone
Asthma and/or allergies or autoimmunity (immune system over active).
Lack of personal space
In the early 19th century, doctors realized that the two halves of the brain might not be identical. By observing people with brain injury they noticed that left sided brain injury affected language where as right-sided brain injury did not have the same effect. In the early 1960’s, Roger Sperry conducted experiments which completely changed the way the neuroscience community thought about brain function. Working with a patient suffering epilepsy he severed the corpus callosum, this resulted in decreased seizure activity but less loss of overall function than expected. Sperry was able to test functions of the right and left hemispheres independently and his results helped chart a map of the brain. Whilst the findings are not absolute they showed the left hemisphere was specialized for language and the right for visual construction tasks. The findings were taken and simplified and the myth of people being left brained or right brained was born from an article in the New York Times magazine and Time magazine.
“Neuroscience has long understood that in order for the human brain to function wholly, large areas of the brain as well as left and right hemispheres continuously use electrical impulses to communicate. This is essential because each hemisphere performs different functions that allow us to react to the world in which we live. More recent research, however, shows that the two sides of the brain do not mature at the same rate the electrical impulses between the two sides get out of balance and interfere with communication.” Dr Robert Melillo (Chiropractor), Disconnected Kids.
A Chiropractic Perspective When we use a hemispheric model in chiropractic practice we are looking to evaluate which hemisphere is under performing and needs increased stimulation to create better balance between left and right. Thankfully due to neuroplasticity the brain has the ability to change given the appropriate input.
A decrease in hemisphere function will decrease the firing to the Pontomedullary Reticular Formation (PMRF) which usually inhibits the sympathetics. This will create:
Increased sympathetic firing
Decreased tone of extensor muscles with relative increased flexor muscle activation above T6
Decreased flexor tone with relative increased extensor activation below T6
This will affect posture and pain syndromes accordingly. The hemisphere has contra-lateral conscious motor and sensory connections and sets tone unilaterally.
A postural assessment will usually include the following on the same side of the hemispheric weakness:
Head tilt, low ear
Shallow creases of muscles of facial expression
Centre of palate will deviate away
Tongue protrusion will demonstrate deviation toward side of hemisphericity
Shoulder rotated anteriorly and internally rotated with the back of the hand more visible
Elbow increased bend
Weak distal muscles in thumb and fingers and big toe
There are a range of other characteristics that are considered in history and evaluated in examination including motor, sensory, vestibular, emotional, behavioural, academic, immune and autonomic.
If there is a clear and congruent clinical picture, we adjust as appropriate and indicated with the aim of increasing afferent stimulation. Follow up with specific home-care advice and sensory-motor exercises based on examination results to further facilitate hemispheric stimulation is frequently additionally advised.