Explain how acquired brain injury and neurological disorders affect cognition and behaviour, and describe how neuroplasticity supports recovery of function

What this dot point is asking

QCAA wants you to explain how damage to the brain, whether through injury or disease, disrupts individual thinking, and to connect specific damaged regions to specific cognitive and behavioural changes. You then need to explain how the brain attempts to recover through neuroplasticity and rehabilitation. This dot point applies the principles of localisation and plasticity to real disruptions of cognition.

The answer

Brain trauma and neurological disorders show what happens when the structures behind individual thinking are disrupted. Because particular functions are localised to particular regions, the location of damage predicts the kind of deficit, which is why these cases also provide evidence for localisation.

Types of acquired brain injury

Acquired brain injury (ABI) refers to any brain damage that occurs after birth, as opposed to congenital conditions. It is divided into two types.

• Traumatic brain injury (TBI). Caused by an external physical force, such as a blow to the head in a fall, car accident or contact sport. Concussion is a mild TBI; severe TBI can involve bleeding, swelling and widespread axonal damage.
• Non-traumatic (internal) brain injury. Caused by internal events such as a stroke (interrupted blood supply), tumour, infection (encephalitis), oxygen deprivation, or a degenerative disease such as Alzheimer's.

How damage disrupts cognition

Specific deficits follow from the function of the damaged region, illustrating localisation in reverse.

• Frontal lobe damage disrupts executive function, planning, impulse control and personality, as in the historical Phineas Gage case.
• Damage to Broca's area (left frontal) produces Broca's aphasia: speech is non-fluent and effortful but comprehension is largely intact.
• Damage to Wernicke's area (left temporal) produces Wernicke's aphasia: speech is fluent but meaningless and comprehension is impaired.
• Hippocampal damage produces amnesia, especially the inability to form new long-term memories (anterograde amnesia), as in the famous patient HM.
• Right parietal damage can cause spatial neglect, where the person ignores the left side of space.

Neurological disorders

Neurological disorders are diseases of the nervous system that progressively or suddenly impair cognition. Examples include Alzheimer's disease, which degrades memory through neuronal loss in the hippocampus and cortex; Parkinson's disease, which affects movement through loss of dopamine-producing neurons; and epilepsy, where abnormal electrical activity can disrupt consciousness and, in severe cases, has historically been treated by severing the corpus callosum (producing split-brain patients).

Recovery through neuroplasticity

The brain is not fixed, and after injury it attempts to recover function through neuroplasticity, the same mechanism that supports learning.

• Rerouting and sprouting. Surviving neurons grow new connections and take over functions previously handled by damaged tissue.
• Reorganisation. Other, undamaged regions can adopt the lost function, especially in younger brains.
• Recovery of dormant tissue. As swelling subsides, areas that were temporarily suppressed (in a state called diaschisis) can resume working.

Recovery is generally greater when the injury occurs early in life and is supported by intensive, repeated practice through rehabilitation. Constraint-induced movement therapy, for instance, forces use of an affected limb to drive plastic rewiring.

Putting it together for an exam

A strong answer names the type of injury, links the damaged region to the specific deficit using a named example, and explains recovery through a named plastic mechanism. For example: a stroke (non-traumatic ABI) damaging Broca's area causes non-fluent aphasia, and rehabilitation supports recovery as surviving neurons sprout new connections that gradually take over speech production.