Autism: a diagnosis that often leaves parents in a panic. Although many individuals with the condition are able to live healthy lives, they will often require ongoing support and face a world that has yet to comprehend their plight. With no cure and a lack of successful treatment, the situation appears bleak. This may all change thanks to a major breakthrough in the quest to better understand the cause of autism, which has eluded scientists for decades. Although the disorder is largely understood to be genetic, the mechanisms within the brain that result have been tough to pin down. A new study published in Neuron helps shed light on this topic, suggesting that children who develop autism have an oversupply of synapses in some parts of the brain.
During infancy, the brain is constantly soaking up new information. In fact, a three-year-old’s brain is two times more active than an adult’s brain. Connections are constantly forming that allow neurons to send and receive signals through synapses. In childhood and adolescence, the brain starts to trim those synapses, limiting their number so other areas can develop specialized functions and are not overloaded with stimuli. This is the brain’s way of becoming more efficient. Like hoarders of synapses, the autistic brain holds on to an abundance of these connections and are unable to get rid of what is not necessary. This insight may set the stage for the development of treatments to aid the brain in disposing of extra synapses.
Inside the Autistic Brain
The study was conducted by a team of researchers from Columbia University’s Medical Center who examined brains of 48 deceased individuals, including 26 who had autism and the rest with normal brain function. Of the brains from those with autism, half came from children aged 2-9 years, while the remaining came from subjects aged 13-20 years– which allowed the team to track development over time. The focus was on an area of the brain with heavy involvement in social behavior and communication. The team zeroed in on spines, the tiny neuron protrusions that receive signals via synapses. More spines indicate more synapses, which was the case for children with autism.
These images demonstrate the lack of pruning that occurs with the neurons of an autistic brain (left) compared to a brain from the control group (right). The spines indicate the locations of synapses.
The age variation of the examined brains showed that younger brains had a similar number of spines while older brains had significant differences. A typical 19 year old had 41 percent fewer synapses than toddlers, but the same age group with autism had only 16 percent fewer than children diagnosed with autism. This evidence allowed scientists to conclude that the problem is a matter of not clearing out unnecessary synapses, rather than an overproduction of synapses.
“More is not better when it comes to synapses, for sure, and pruning is absolutely essential,” said Lisa Boulanger, a molecular biologist at Princeton who was not involved in the research. “If it was overgrowth, you’d expect them to be different from the start, but because the synapse difference comes on so late, it’s probably pruning.”
Further evidence of this finding came from a lack of autophagy, the body’s way of cleaning out degraded cells, in people with autism. “They showed that these markers of autophagy decrease” in autism-afflicted brains, said Eric Klann, a professor of neural science at New York University. “Without autophagy, this pruning can’t take place.”
Stopping Autism in its Tracks
Think about the last time you were overloaded with information and given little time to process. Now imagine this happening to you constantly with no ability to filter. This is what scientists imagine is happening in the brains of children with autism, and may explain certain symptoms like oversensitivity to noise or social experiences. These findings arm scientists with the knowledge to combat autism by developing therapies to clear the extra synapses. As the fastest growing developmental disability in the U.S., affecting 1 in 68 children, there is no doubt that a thorough understanding of autism will have a far-reaching impact.
Researchers have struggled to understand how the brain operates for someone with autism. This new insight goes deeper to explain the root causes within the brain that present the disability and provides hope for an effective treatment. “The pruning problem seems to happen later in development than one might think,” Dr. Klann said. “It suggests that if you could intervene in that process that it could be beneficial for social behavior.”
A recent report, “Changing Trends of Childhood Disability, 2001-2011″ found the number of American children with disabilities rose 16% over a 10-year period. While there was actually a decline in physical problems, there was a large increase in neurodevelopmental conditions such as ADHD and autism. Although it is difficult to determine whether the rates are attributable to increased awareness and a subsequently higher rate of diagnosis, many experts feel that there is enough conclusive evidence to support an overall increase in occurrence. And if this is the case, then time is crucial if experts are to put the brakes on autism.
- New York Times|Brains of autistic children have too many synapses
- New York Times|The Kid Who Beat Autism
- Detroit Free Press|Parents reporting more cases of disability in children