Recently, researchers at San Diego State University
researchers may have decided the winner of an ongoing battle between competing
theories of autism spectrum disorder. This disorder, often referred to simply
as autism, actually describes a wide range of individuals with social deficits
communication problems and repetitive behaviors . Autism has puzzled
researchers since Leo Kanner first described it in 19431. Most
individuals with autism have normal IQ’s and extremely variable levels of
social deficits2. These social deficits can range from the inability
to use and understand language at all, to having trouble holding reciprocal
conversations with others. While there are countless theories as to what causes
the social deficits in autism, two are emerging as frontrunners.
 |
| Children with autism often prefer to play alone instead of with other children. Photo from Simons Foundation Autism Research Initiative |
One theory of autism is the Mind Blindness Theory. According
to this model, the social deficits in Autism Spectrum Disorder are caused by
dysfunction in the area of the brain that is responsible for abstract
processing of other’s intentions3. This area of the brain is crucial
to understanding and interpreting the words and actions of others. Being able
to infer another person’s mental state is known as Theory of Mind. Imagine you are in your friend’s house on a
chilly fall day, and you are uncomfortably cold. You notice the window is open
and say “It sure is cold in here today.” Your friend walks over to the window
and closes it. Your friend has just used Theory of Mind to interpret your
statement as a request to close the window. A person with Autism may respond to
your statement by agreeing that it is cold, not understanding that your
statement was actually a request for them to get up and close the window.
The other theory of autism is based on dysfunction of the
Mirror Neuron System. In the area of the brain that initiates movement, such as
picking up a fork, there are neurons that will also fire the exact same way in response to someone else picking up a fork.
Before the discovery of mirror neurons, it was thought that neurons in the area
of the brain responsible for initiating movement had only that one specific
purpose. Some scientists believe that these neurons that fire to initiate
action as well as fire in response to other people performing actions help
people to understand the actions of others. It is hypothesized that there is
problem with these neurons in Autism, leading to problems interpreting the
actions of others4.
So which theory was declared to be the winner? Both. The
results of the study described below showed that not only are there problems in
both systems, but the communication between the two systems seems to be
different in adolescents with autism.
Inna Fishman and her colleagues were interested in examining
what differences in brain connectivity they could find in adolescents with
autism, and how these differences in brain connectivity translate into social
impairment. In other words, they were attempting to determine if a higher
degree of abnormality in the brains of individuals with autism would manifest
as more severe social impairment5.
Fishman technique called fcMRI (functional connectivity
magnetic resonance imaging) which measures the way the brain is connected while
a person is at rest. The study included 25 adolescents (ages 11-18) with autism
and 25 adolescents without autism.
The results of the study showed evidence of less
connectivity in the Theory of Mind brain region in those with autism compared
to those without autism. Less connectivity suggests that the individual neurons
in this section of the brain are not communicating with the neurons around them
in a typical manner. In other areas associated with the Theory of Mind
processes they found an increase in connectivity, which has been shown by other
researchers. These results provide support for the Mind Blindness Theory of
autism.
The most significant finding by Fishman was the increase in
connectivity between the Theory of Mind system and the Mirror Neuron System.
Further, in a subset of the sample, the amount of connectivity was correlated with
higher levels of social impairment. Adolescents with autism who had the
greatest amount of connections between the two brain areas also had the most
severe social deficits. Fishman and her colleagues have hypothesized that both
the Mirror Neuron System and the Theory of Mind portion of the brain are not
function normally in people with autism, which leads to increased connectivity
and communication between the two areas in order to make up for the dysfunction
taking place in each of the two areas.
 |
| This figure highlights the areas of heightened connectivity between the Theory of Mind and Mirror Neuron brain areas. Image from Fishman et al. |
While this is certainly an exciting new development in
autism research, it is important to understand the limitations of this study.
Given that this was an imaging study that looks at the brain after the onset of
the disorder, we cannot claim causality. It is not possible to determine whether
the differential connectivity causes the social symptoms, or if the increased
connectivity develops as a result of dysfunction in the Mirror Neuron system
and brain regions involved in Theory of Mind processing. With these limitations
in mind, it appears as though both scientists studying the Mind Blindness
Theory and the dysfunction of the mirror neuron system may be on the right
track to solving a piece of the autism puzzle.
References
1. “Autism at 70-From Kenner to the DSM-5,” What We’ve Learned About Autism. September
2013. Autism Speaks. Retrieved from https://www.autismspeaks.org/science/science-news/autism-70-–-kanner-dsm-5
2. “Autism Fact Sheet” November
2014. National Institute of Neurological
Disorders and Stroke. Retrieved from http://www.ninds.nih.gov/disorders/autism/detail_autism.htm
4. Dapretto,
M. et al. Understanding emotions in others: mirror neuron dysfunction
in children with autism spectrum disorders. Nat. Neurosci. 9,
28–30 (2006)
Are there any theories as to what causes these abnormalities in Theory of the Mind processing and mirror neuron function? Is it caused by a genetic mutation, something that happens during pregnancy, environmental factors, bacteria/viruses?
ReplyDeleteScientists have identified many different risk factors for Autism including several genetic factors, environmental pollutants and other environmental factors, and the age of parents. Some scientists have even argued that women in the workplace and the internet may have allowed people with symptoms of autism to meet and have kids, passing along more autism traits. For example, the stereotypical somewhat weird engineer may not have had the social skills or the desire to go out to a bar to meet women before, but now that there are female engineers working with him he has a better chance of finding a partner. While obviously this THE answer, it is really interesting to think about. If you are interested in it try looking up BAP, or the broader autism phenotype which runs in families of children who are diagnosed with autism.
DeleteAre there any theories as to what causes these abnormalities in Theory of the Mind processing and mirror neuron function? Is it caused by a genetic mutation, something that happens during pregnancy, environmental factors, bacteria/viruses?
ReplyDeleteI have a few friends with mild autism, but I never knew much about the condition. The mirror neuron system and mind blindness theory do an excellent job of summarizing what is missing in a person with autism. Probably the most obvious difference in those with autism, even when it's mild, is a disconnect in communication. Although this research does not specify the cause of autism, I think it is an important step in understanding this condition. Autism is so widespread and so difficult to understand, so it's great to see that some progress is being made, even though a full understanding of autism seems to lie in the distant future.
ReplyDeleteAs you pointed out, there is not really a way to examine causality, not only due to the fact that it is a study based on neuroimaging, but also because of the fact that there are not any controls or variables that are really able to be studied. I think that it would be really interesting to see results of a twin study or a study looking at siblings, to see if there are any differences that can be observed that may provide a stronger indication of the basis for the disorder.
ReplyDeleteAs you pointed out, there is not really a way to examine causality, not only due to the fact that it is a study based on neuroimaging, but also because of the fact that there are not any controls or variables that are really able to be studied. I think that it would be really interesting to see results of a twin study or a study looking at siblings, to see if there are any differences that can be observed that may provide a stronger indication of the basis for the disorder.
ReplyDelete