Autism Awareness Week: The Neurological Science Behind Autism

0


Defined by the NHS as a ‘range of conditions that affect a person’s social interactions, communication skills and behaviour‘, Autism spectrum disorder affects 1 in 100 people in the UK alone, and around 1% of the wider global population. 

Diagnosis of ASD (which includes autism and Asperger’s syndrome) is usually made in children around 3 years of age, and while extensive therapy and support systems are in place, no definite cure has yet been discovered. The exact cause of the condition is also a mystery, but many sources point towards a genetic connection between sufferers, with scientists hard at work to identify any ‘susceptibility genes’ that may get passed on from generation to generation within families. One thing is clear however: there is no connection between autism and the MMR vaccine typically administered to children, despite what the claims of Dr Andrew Wakefield in 1998 might have had you believe.

An analysis of the differences between a normal human brain and an autistic one can begin to shed some light on the causes of ASD, and why the condition may cause issues with interpersonal interactions in those who have it. Firstly, autistic infants typically show extremely late development of their vocal skills, with many not saying their first word(s) until 2 years of age. This has been attributed to dampened activity in the temporal and parietal lobes of the brain – tissues that are associated with the language centres of an individual. Similarly, researchers at Cambridge have discovered that the amygdala region (within the temporal lobe) responsible for the formation and storage of memories associated with emotional events is usually less active, explaining the difficulty that older child sufferers face with maintaining eye contact and decoding the facial expressions and body language of others. This results in autistic children then typically showing a lack of awareness and/or interest in others within their age group, which all stems from dysfunctional brain regions (responsible for social skills) and lack of synchronicity between them.

One interesting fact to note is that ASD seems to be far more prevalent in males than females. Researchers have hypothesised that testosterone (an important male sex hormone) may affect the brain development of baby boys while still in the womb by binding to androgen hormone receptors in the brain, of which the amygdala region mentioned previously has numerous amounts of. With this in mind, Cambridge scientists recently determined that higher pre-natal testosterone levels were associated with reduced social skills but superior attention to detail in infants; common traits of autistic individuals. However, the causes of this difference in brain development (resulting from heightened testosterone levels in the developing foetus) are unclear; again scientists suspect genetics may come into play.

Perhaps the closest that researchers have ever come to determining the origins of autism was during a recent study at Columbia University. In the paper that they published in the journal, ‘Neuron’, it was found that sufferers all have a surplus of synapses (connections between neurons – the basic functional units of the nervous system). In normal individuals, a burst of synapse formation occurs in childhood, but around 50% are eliminated in adolescence during a ‘pruning’ stage. For whatever reason (again, possibly genetics and/or other environmental factors) this ‘pruning’ of synapses does not occur with autistic individuals, resulting in the dysfunction of the nervous system mentioned earlier.

Research into these findings is still ongoing, but scientists have theorised that this information could be used to provide a treatment for autism. The hypothetical drug, rapamycin, is already in use as a treatment for patients who have recently received an organ transplant to prevent rejection of the new body part by their immune system. In a study of mice with a mutation that gave them a surplus of synapses, it was found that treatment with rapamycin both reduced the number of synapses and improved their social behaviour, possibly paving the way for a landmark treatment of the symptoms of autism. However, rapamycin is known to have severe side effects, including suppression of the immune system, lung inflammation and increased susceptibility to diabetes. As a result, the drug is clearly not yet appropriate to administer, but this study is nevertheless an extremely useful first step in developing a treatment for ASD.

Credit: Pixabay

While the origins of autism are still a mystery for now, it is a matter of time before a fuller understanding of this condition which affects millions of people worldwide is found. In the meantime, while the top researchers of this topic work in some of the most state of the art laboratories across the world, an insight into what makes the autistic brain unique can at least help to foster an understanding of the condition and those with it.

avatar

Leave A Reply