Changes in prefrontal axons may disrupt the network in autism

Area of Science:

• Neuroscience
• Autism Spectrum Disorder Research
• Developmental Neuroscience

Background:

• Neural communication is disrupted in autism, but the underlying mechanisms remain unclear.
• Axons, the communication lines of neurons, are critical for brain function and have been implicated in autism pathology.

Purpose of the Study:

• To investigate alterations in the ultrastructure of single axons in the white matter of postmortem human brains from individuals with autism.
• To examine specific prefrontal regions (ACC, OFC, LPFC) consistently implicated in autism.

Main Methods:

• Microscopic examination of single axons and their ultrastructure in postmortem human brain white matter.
• Analysis of axonal size, density, and myelin thickness in specific prefrontal areas (below ACC, OFC, LPFC).

Main Results:

• Reduced large-diameter axons and increased thin axons below the anterior cingulate cortex (ACC), with associated growth-associated protein 43 kDa overexpression.
• Decreased myelin thickness in axons below the orbitofrontal cortex (OFC).
• Altered white matter composition below ACC and OFC impacted connectivity across prefrontal areas.

Conclusions:

• Findings suggest mechanisms for pathway disconnection, excessive local connections, and inefficient emotional processing in autism.
• These axon alterations may explain key autistic behaviors like attention difficulties and social avoidance.
• Developmental changes in axon growth and guidance are implicated, suggesting potential therapeutic targets in autism.