Researchers at the Columbia University Medical Centre have identified distinguishable factors between brains with autism and brains without. The study, conducted in the lab of neurobiologists Dr. David Sulzer, was published in the peer-reviewed journal Neuron.

Autism spectrum disorders (ASD) are characterized by the signature impaired social interaction, communication difficulties, restricted and repetitive patterns of behaviour in individuals. There is currently no cure, and much is still unknown about the disorder, including the root cause. Various studies have pointed to possible range of biological and environmental cause factors.

Dr. Sulzer’s team examined brain tissue from 26 autistic children who had died from other causes, and 22 healthy children. The number of spines extending from neurons and forming synapses (connections) with other neurons was painstakingly counted in the region of the brain involved with social and communication processes, the area implicated in autism.

Researchers discovered that each of the 26 autistic brains were approximately 50 to 66 percent higher in synaptic density than the healthy brains, suggesting that autism could be the result of hyper-connectivity in the brain. They further found that by late childhood, spine density decreased by 41 percent in healthy brains, compared to a decrease of just 16 percent in the autistic brains.

The study suggests that unlike in healthy brains, there may be a lack of pruning of connections in autistic brains. The hypothesis is supported by the literature, much of which cites the role of autism-linked genes in synapse pruning. Understanding the function of the molecules involved in this pathway, particularly the role of the protein mTOR in hindering the pruning process, could aid in the development of a pharmacological treatment for autism. Protein mTOR is highly involved in the regulation of cell growth and neurite plasticity.

Researchers further examined this pathway in genetically engineered mice with impairments similar to autism. Mice were treated with a drug meant to counteract the hyperactivity of protein mTOR, to assess its ability to interfere with the pathway. Mice that received treatment saw marked improvement from symptomatic autistic behaviours. Researchers concluded that there was a direct relationship between limiting mTOR activity and increased pruning of neuronal connections.

The drug used by researchers, rapamycin, is typically used to prevent the body’s natural tendency to reject organ and bone marrow transplants. But due to the serious adverse effects associated with the use of the drug, it will most likely be discouraged for use in paediatric therapies.