Monday 12 August 2013

Genetic Basis for Autism

I've been reading Bruce Hood's The Self Illusion: How the Social Brain Creates Identity and in one of the sections, he mentioned two really interesting theories for a genetic basis for autism.

The first involves brain imaging studies looking the frontoinsular (FI) and anterior cingulate cortex (ACC)  which are activated by social interaction.  Scans show that these two areas operate differently in people with autism than they do in neurotypical individuals. 

Okay, time for a brief psychology lesson from an admitted non-expert.  Neurotypical people will mirror those around them as part of social interaction.  People unconsciously mimic poses, facial expressions and movements.  This is part of how we are able to intuit how other people around us are thinking.  By mimicking them, we trigger similar emotions in ourselves and thus can guess what they're feeling and experiencing.  People with autism often don't mirror those around them.

The FI and the ACC are both involved in the mirroring process.  The ACC is "like an 'alarm center' that monitors goals and conflicts, including social interactions.  If these interactions do not go according to plan, if people start to get the wrong idea out to us, we get anxious."  Since people with autism are rarely able to predict social interactions, the alarms go off frequently, making social interactions even more difficult and unpleasant.

There is debate about whether the differences in brain activities are the result of a lack of observation (people with autism often find it uncomfortable or overwhelming to look at faces, cutting out a lot of the non verbal cues available to help them interpret and predict other people's reactions) or if this is a cause for the lack of mirroring ability found in a lot of people with autism.

Mirroring is one of those vital early childhood development tools which help babies and toddlers learn to be part of the human social environment.  Children who are isolated during these critical phases either learn to mirror something inhuman (if exposed to animals) or simply never learn to fit in with any level of comfort.  I know this is one of the things which Nathan's therapist focused on very early on, getting him to pay attention to her and mimic what she did.

The second theory is from a neuroscientist, John Allman, who suggested that "the social deficit in autism may be based on a lack of a special class of spindle neurons called Von Economo neurons (VENs)."  These neurons have highly connective fibres and branch out to different brain regions that are activated by social learning.  They are found in social species like whales, elephants and apes.

Humans have a lot of VENs in our FI and ACC regions and are thought to keep track of social experiences, which would let us build up a catalogue of possibilities and help us to predict future experiences.  The density of VENs increases from infancy to age four, when they reach adult density.  This matches the window for effective early intervention for autism, giving a potential biological explanation for why treating autism early can help to greatly minimize adult symptoms.

Again, there is a chicken and egg debate about this.  Does a lack of VENs make it harder for children with autism to store and explore social experience or does a lack of observation fail to stimulate VENs growth?  Either way, it still suggests possible treatment directions.

With my family's experience, I am a firm believer that there is a genetic component to autism.  (Personally, I think we'll discover that several different conditions produce the same autism effect, but that's a separate blog.)  My husband is on the spectrum, my children are on the spectrum and we have reason to believe there's even more autism on the family tree, going far back beyond modern parenting and environmental toxins.

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