Neural pruning and the adolescent brain

Psychologists taking a biological approach seek to understand how neural networks develop over a life span and in response to environment or injury.

While repetition and learning strengthens some networks, others are lost due to neural pruning. The term ‘neuroplasticity’ is used to describe these processes.

Developmental psychologists are particularly interested in the period from childhood to adulthood, as the brain undergoes a major remodelling through neural pruning and myelination (myelin is a protein and fatty substance that can form a sheath on a neuron to speed neural firing).

Petanjek et al. (2011) investigated the process of neural pruning in the prefrontal cortex.

Aim: Determine the extent of neural pruning during puberty and early adolescence.

Type of study: Post-mortem examination of brain tissue using the Golgi method of dendritic spine detection.

Participants: 32 subjects (9 females and 23 males) ranging in age from 1 week to 91 years old. All subjects lived under standard environmental and socioeconomic conditions. The brains were collected with the approval of the Ethical Committee of the University of Zagreb.

Procedures: Golgi staining of prefrontal brain tissue of subjects followed by quantitative analysis to determine dendrite density.

Results: Density increased significantly during infancy and reached its peak during childhood. Density diminished during late childhood and adolescence. Dendrite density stabilised around 30 years old and remained constant between 38 to 65 years.

Conclusion: Plasticity of the frontal cortex continues into adulthood and provides the opportunity to acquire higher order cognitive abilities though there is a higher risk of abnormal circuitry that can be expressed in neuropsychiatric disorders.

The study report can be assessed here.