The human brain weighs about 1400g which is similar in weight to a cantaloupe. It looks like a large pinkish-grey walnut. It is made up of about 86 billion nerve cells and it is estimated that 20-25% of our total energy budget goes towards running our brain (Herculano-Houzel, 2016). The brain is like a control center- it controls our automatic processes, such as breathing, heart rate and regulating our body temperature, as well as the more intentional processes including movement, speech, thinking, emotions and our behavior. Given how complex our brain is, it is not surprising that each brain injury can be different.
To understand the impact that an injury can have on the brain, it is helpful to explore the parts of the brain and their main function. Damage to a specific brain region can impact on the function/activity that is controlled by that brain region. It is also important to recognize that the brain is interconnected, so damage to one specific area may disrupt abilities mediated by another brain area due to the connections between these regions. The largest part of the brain is the cerebral cortex which is the outer layer of the brain. The cortex is divided into halves or hemispheres. The left hemisphere controls the right side of the body and the right hemisphere controls the left side of the body. In most people, the left hemisphere also controls language function, whereas the right hemisphere controls visuo-spatial skills and music abilities. So if someone has an injury involving only the left side of the brain, they may have difficulty speaking and moving their right arm and leg. The cortex can be divided into four main areas or lobes.
Click on the coloured areas on the brain diagram to see the function and common difficulties observed after injury to each area.