Explain neuroplasticity, including developmental and adaptive plasticity, the mechanisms of synaptic change, and how the brain reorganises after injury

What this dot point is asking

QCAA wants you to explain that the brain is not a fixed structure but a dynamic organ that changes its physical wiring throughout life in response to experience, learning and injury. You need to distinguish the two main types of plasticity, name the cellular mechanisms involved, and explain how reorganisation supports recovery from brain damage.

The answer

Neuroplasticity (also called neural plasticity or brain plasticity) is the capacity of the brain to change its neural structure and function in response to experience, learning, environmental change and injury. It overturns the older view that the adult brain is fixed and unchangeable.

Developmental plasticity

Developmental plasticity refers to the changes that occur as the brain matures from infancy through adolescence. The young brain is built and refined through several processes.

• Proliferation. The generation of new neurons before birth, eventually producing billions of cells.
• Migration. Neurons move to their final positions in the developing brain.
• Synaptogenesis. The rapid formation of new synapses (connections between neurons), which peaks in early childhood.
• Synaptic pruning. The selective elimination of synapses that are rarely used, following the principle of "use it or lose it". Pruning makes neural processing more efficient and continues into the early twenties, particularly in the frontal lobe.
• Myelination. The coating of axons in a fatty myelin sheath that speeds up neural transmission, continuing well into adolescence.

This sequence explains why young children learn certain skills, such as language, with greater ease than adults: the brain is at its most plastic during these sensitive periods.

Adaptive plasticity

Adaptive plasticity refers to the brain's ability to compensate for lost function or to maximise remaining function after damage, and to rewire itself in response to ongoing learning in adulthood. Two key mechanisms are involved.

• Sprouting. Undamaged neurons grow new branches (dendrites or axon terminals) to form new connections, replacing those lost to damage.
• Rerouting. A damaged neuron forms a new connection to an undamaged neuron, creating an alternative pathway around the area of damage.

Adaptive plasticity is why a person who suffers a stroke may, with rehabilitation, regain functions such as speech or movement: surviving regions take over tasks previously handled by the damaged area.

Long-term potentiation and learning

At the cellular level, learning relies on long-term potentiation (LTP), the long-lasting strengthening of the connection between two neurons that fire together repeatedly. Donald Hebb captured this in the principle often summarised as "neurons that fire together, wire together". Repeated stimulation makes the receiving neuron more responsive, so the pathway becomes more efficient. LTP is widely regarded as the cellular basis of learning and memory, linking plasticity directly to the formation of long-term memories.

Recovery from brain injury

The brain's response to injury shows adaptive plasticity in action. After damage, surrounding healthy tissue can reorganise to take on lost functions through sprouting and rerouting. Several factors influence the extent of recovery.

• Age. Younger brains are generally more plastic and recover more completely, though this is not absolute.
• Rehabilitation. Targeted practice and therapy drive reorganisation by repeatedly activating the relevant pathways.
• Severity and location of damage. Smaller lesions in less specialised regions allow fuller recovery.

Plasticity across the lifespan

Although plasticity is greatest in early childhood, it continues throughout life. Adults form new connections every time they learn a skill or fact, which is why studying, practising an instrument or learning a language physically changes the brain. The maturation of the prefrontal cortex through synaptic pruning and myelination into the mid-twenties also helps explain adolescent risk-taking, since the regions governing impulse control are still being refined.

Putting it together for an exam

Define neuroplasticity, then distinguish developmental plasticity (synaptogenesis, pruning, myelination in the maturing brain) from adaptive plasticity (sprouting, rerouting, recovery from injury and adult learning). Name LTP as the cellular mechanism of learning and link it to memory. A strong answer connects a process to a real consequence, such as linking pruning to efficient processing or rerouting to stroke recovery.