Synaptic pruning is the process in which the brain removes neurons and synapses that it does not need. This usually takes place when a person is 2–10 years old.

The brain contains millions of neurons that communicate with one another using a combination of electrical and chemical signals.

Synapses are the places where these neurons connect in order to function. Synaptic pruning is the natural process where the brain eliminates extra synapses that it does not require.

Read on to learn more about synaptic pruning, including how it takes place and its potential link with certain conditions.

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The neurons in the brain meet and connect at the synapses.

Synaptic pruning is the process where the brain eliminates extra neurons and synapses. This can help increase the efficiency of the brain’s neural transmissions.

Neurons and synapses begin to form during the earliest stage of an embryo’s development. From this point until a person is approximately 2 years old, new neurons and synapses form at an extremely fast rate. At times, 40,000 new synapses may form each second.

At the end of this stage of development, when a person is around 2 years old, they have far more neurons and synapses than they will functionally need.

As infants learn and grow, their experiences strengthen the synapses that prove to be the most relevant. Other synapses in the brain weaken and fade.

Synaptic pruning is the natural process where the brain eliminates extra synapses. This helps form a healthy and adaptive brain.

The brain uses the amount and timing of neural activity to determine which synapses it needs to reinforce and which it needs to retain.

The brain also uses the amount and timing of neural activity to determine which synapses become weaker. It then flags these synapses, and the brain destroys them.

Imaging studies suggest that elements of a person’s immune system play an essential role in eliminating these synapses.

Glia are non-neuronal cells in the brain and the most abundant cells in the central nervous system. There is some evidence that glia participate in sculpting neuronal circuits. They may do this by engulfing synapses as part of the synaptic pruning process.

Synaptic pruning tends to begin when a person is around 2 years old. By the time they are approximately 10 years old, a person’s brain will have removed almost 50% of the synapses that were present at 2 years old.

Research suggests that incorrect synaptic pruning may play a role in the development of certain neurological disorders.

Schizophrenia is a mental health condition. It can cause a person to experience:

Studies suggest that incorrect pruning, resulting in too much or too little pruning, may contribute to the development of schizophrenia.

Postmortem examinations show that synapse density is lower in people with schizophrenia compared with people without the condition. This suggests that people with schizophrenia may have experienced increased synapse elimination.

However, synaptic pruning may not be the main factor in the development of schizophrenia. Evidence suggests that people with schizophrenia may also have changes in:

Scientists believe that a process in the brain called the excitation/inhibition (E/I) ratio is essential for circuit function and stability. Neurons and circuits in the brain coordinate their inputs to help establish and maintain a constant ratio.

Impairments in synaptic pruning can disrupt the E/I balance of synapses. Studies suggest this disruption may cause certain neurodevelopmental disorders, such as autism spectrum disorder (ASD).

This means that glial cell dysfunction leading to reduced or excessive synaptic pruning may be involved in the development of ASD.

A 2021 study refers to previous research that suggests people with ASD have an increased density of excitatory synapses in the brain. This may support the theory that incorrect synaptic pruning can contribute to the development of ASD.

Synaptic pruning is the process in which the brain removes the neurons and synapses it does not need.

Neurons and synapses begin to form during the earliest stage of an embryo’s development. By around 2 years old, infants have far more neurons and synapses than they need. Synaptic pruning begins to take place at this age and usually continues until around 10 years old. By then, a person will have removed almost 50% of the synapses they had at 2 years old.

There is some evidence that synaptic pruning may play a role in the development of autism spectrum disorder and schizophrenia.