Children with Autism have extra synapses in the brain
Dr Shelley Hyman
A study from the Columbia University Medical Centre has discovered that children and adolescents with autism have an excess of synapses in the brain. This excess is due to a decline in normal brain ‘pruning’, a neurological regulatory process which reduces the overall number of neurons and synapses, enabling more efficient synaptic configurations. Since synapses are the point where neurons connect and communicate with each other, the additional synapses may have a significant impact on the functioning of the brain.
Researchers have found a drug that restores normal synaptic pruning and reduces autism like behaviours in mice, even when the drug is administered after the behaviours have appeared. The drug, rapamycin, has side effects which may render it inappropriate for use on humans. However, the senior investigator says that the mere observable change in autism- like behaviours suggests that autism may be treatable, if a better drug can be discovered.
The cause of the pruning defect can be linked to the fact that the autistic children’s brain cells were filled with old and damaged parts, and were deficient in a degradation pathway known as “autography”, a process that cells use to breakdown their own components. The pruning defect has been linked to a protein called mTOR. When mTOR is overactive, the brain cells lose most of their ability to breakdown their own components, leading to poor pruning and a surplus of synapses. As such, the “rapamycin” inhibits mTOR.
This research is a remarkable step towards understanding the neurobiology of patients with autism. It could provide a means of diagnosing autism through screening for mTOR and autophagic activity, as well as a possible cure for autism through treatment of synaptic dysfunction.