Neuronal pruning

Neuronal pruning is a natural process during brain development where excess neurons and synaptic connections are eliminated to improve the efficiency of neural circuits. In the context of autism, including regressive autism, altered neuronal pruning has been proposed as a potential contributing factor.

Neuronal Pruning in Autism

1. Hypothesis of Altered Pruning: Some researchers suggest that abnormalities in the neuronal pruning process may contribute to the development of autism. Specifically, it has been hypothesized that either excessive pruning (leading to a loss of necessary neural connections) or insufficient pruning (resulting in too many synapses) could disrupt normal brain function and development (Tang et al., 2014).

2. Evidence from Neuroimaging and Postmortem Studies: Studies using neuroimaging techniques, such as MRI, have observed differences in brain structure and connectivity in individuals with autism. Some findings suggest an overabundance of synaptic connections in certain brain regions, which could be indicative of reduced synaptic pruning (Varghese et al., 2017). Postmortem studies have also reported similar findings, suggesting that reduced pruning may contribute to the atypical brain connectivity seen in autism.

3. Genetic and Molecular Factors: Genetic studies have identified mutations in genes involved in synaptic function and pruning, which may contribute to autism. For instance, mutations in genes like MECP2, SHANK3, and PTEN have been associated with disrupted synaptic pruning and have been linked to autism spectrum disorders (Penzes et al., 2011).

4. Role in Regressive Autism: In regressive autism, where children lose previously acquired skills, disrupted pruning may play a role in the sudden decline of cognitive and social abilities. The exact mechanisms are still under investigation, but it is possible that abnormal pruning could interfere with the stabilization of neural circuits involved in language, social interaction, and behavior.

Citations

• Tang, G., et al. (2014). Loss of mTOR-dependent macroautophagy causes autistic-like synaptic pruning deficits. Neuron, 83(5), 1131-1143.
• Varghese, M., et al. (2017). Autism spectrum disorder: neuropathology and animal models. Acta Neuropathologica, 134(4), 537-566.
• Penzes, P., et al. (2011). Dendritic spine pathology in neuropsychiatric disorders. Nature Neuroscience, 14(3), 285-293.