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Autism Coach

Mirror Neuron Theory of Autism - Part 1


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November, 2006, issue of Scientific American introduced a Mirror Neuron theory of autism that provides an intriguing glimpse into the possible biological underpinnings of autism.  

In the 1990's, scientists discovered through brain imaging technologies that when humans and primates perform voluntary actions (such as reaching for something or pulling a lever), certain brain cells activate in the premotor cortex of the brain's frontal lobe. These activated neurons are called the motor command neurons. Researchers then subsequently discovered that a subset of these motor command neurons was also activated when a human or primate would watch someone else the  perform the same action.  This subset is referred to as mirror neurons.  

It is believed that the mirror neurons, and the networks they are part of, not only enable humans and primates to send motor commands to muscles, but also to determine the intentions of other individuals by mentally simulating their actions.  In primates, the role of the neurons may be limited to predicting simple goal-directed actions, but in humans the mirror neuron system may have evolved the ability to interpret more complex intentions.

Later research has showed that these mirror neurons are located in other parts of the human brain, such as the cingulate cortex and insular cortex, and that they may play a role in empathy and emotional responses. While studying the anterior cingulate cortex of awake human subjects, investigators found that certain neurons that typically fire in response to pain also fired when the person saw someone else in pain. 

To demonstrate mirror neuron dysfunction in children with autism, the authors of the article,  Vilayanur, Ramachandran, and Oberman, used  an electroencephalogram (EEG) to measure children's brain waves. An EEG component called the mu wave is blocked anytime a person makes a voluntary muscle movement, such as opening and closing one's hands. The mu wave is also blocked when a person watches someone else perform the same action.  The researchers watched for  mu-wave suppression to monitor mirror neuron activity.

Their first subject for their experiments was a high-functioning child with autism without severe cognitive impairments. The EEG showed that the child had an observable mu wave that was suppressed when he made a simple, voluntary movement, just as in normal children. But when the child watched someone else perform the action, the mu wave was not suppressed. The researchers concluded that the child's motor command system was intact but that his mirror neuron system was deficient. 

The researchers later conducted a more systematic series of experiments in 10 high-functioning individuals with autism spectrum disorder and 10 age- and gender-matched control subjects. They saw the expected suppression of mu waves when the control subjects moved their hands and watched videos of a moving hand, but the EEGs of the subjects with autism showed mu suppression only when they moved their own hands. These findings indicate that people with autism are likely to have dysfunctional mirror neuron systems.  

The researchers speculate that mirror neuron system may also account for the tendency of autistic individuals to interpret figures of speech literally. Which part of the human brain is involved in this skill of developing overall cognitive maps of understanding from diverse information coming from multiple sensory sources? The angular gyrus, which sits at the crossroads of the brain's vision, hearing and touch centers, seemed to be a likely candidate because nerve cells with mirror neuron-like properties have been found there. Nonautistic subjects with damage to the angular gyrus have difficulty understanding metaphors, as do many people with autism. 

The discovery of mirror neuron deficiencies in people with autism could be used as an early diagnostic tool.  Physicians could use the lack of mu-wave suppression as a diagnostic tool to identify children with autism in early infancy, so that  therapies can be started as quickly as possible. 

The researchers also suggest that biofeedback might used to display the mu waves and then use visual feedback of the display of the mu waves to teach children how to suppress the mu waves, just as biofeedback is used enable people to manifest other brainwave patterns.  A researcher, Pineda, is pursuing this approach, and his preliminary results look promising. 

Another approach is to correct chemical imbalances that disable the mirror neurons. These researchers hypothesize that specialized neuromodulators may enhance the activity of mirror neurons involved in emotional responses. According to this approach, the partial depletion of such chemicals could explain the lack of emotional empathy seen in autism, and therefore researchers should look for compounds that stimulate the release of the neuromodulators or mimic their effects on mirror neurons. 

The Mirror Neuron theory backs up my own observations over the years that the best (and usually only) way to teach my son within the autism spectrum has been to have him do the task himself.  I have found that standing behind him and using my hands to guide him through a new task was often the fastest, most effective way to teach a new skill.   Demonstrating or lecturing was almost always ineffective.  This research has wider educational implications, leading to the logical conclusion that the  typical public school model of children learning from an instructor lecturing up at the front of a room would fail to teach an autistic child.  An autistic child in a traditional classroom would be likely to be bored, frustrated and unable to learn.  However, these same children can learn if they are guided to carry out the actions of the concepts being taught, as is done in teaching them the acquisition of language through therapies such as Applied Behavioral Analysis.  This understanding of how children within the autism spectrum learn could completely redefine what constitutes an appropriate education for autistic children and best practices for teaching them in the public schools.  

A second autism theory described in this issue of Scientific American is the Salient Landscape theory, developed in collaboration with William Hirstein of Elmhurst College and Portia Iversen of Cure Autism Now.  The Salient Landscape theory may may explain other symptoms of autism, such as repetitive motions such as rocking to and fro, avoidance of eye contact, hypersensitivity, and aversion to certain sounds. 

During every waking moment, a person is flooded with sensory information from eyes, ears, nose, and other areas of sensory input.  In order for the body make sense of this information so a person can react appropriately to it, this information proceeds from the brain's sensory organs to the amygdala, which connects to the limbic system that regulates our emotions.  Using feedback from previously stored knowledge, the amgydala determines how a person should respond emotionally to the sensory input they are receiving.  Some of the primary emotional responses include fear, lust, and indifference.  Emotional responses from the limbic system ripple through to the autonomic nervous system that controls the actions that are done for our bodies automatically (such as breathing, pumping blood, and sweating).  The autonomic nervous system responds appropriately to sensory input to prepare the body for action.  For example, the sight of a burglar would cause the heart rate to rise in preparation for a person to physically respond (fight or flight).  The autonomic response in turn, feeds back to the brain, further increasing emotional response.  As a child develops and matures, his or her amygdala is shaped by previous experiences to create a salient or emotional landscape that colors the significance of everything in the individual's environment.

The sensory input of children within the autism spectrum is believed to be interpreted in a distorted fashion due to abnormal connections which may occur between different areas of the brain, including the sense organs and the amygdala, the limbic structures and the frontal lobes.  As a result of these abnormal connections, the emotional landscape is also distorted and events which would not cause a strong reaction in a neurotypical child could set off an extreme emotional/autonomic response in an autistic individual.  Due to sensory distortion, people with autism have often reported great discomfort from sensory input such as sound, touch, and types of lighting, that would not be perceived as uncomfortable or painful by non-autistic people.

The researchers found some support for this hypothesis when they monitored autonomic responses in a group of 37 children with autism by measuring the increase in their skin conductance caused by sweating. In contrast with the control subjects, the children with autism had a higher overall level of autonomic arousal. Although they became agitated when exposed to trivial objects and events, they often ignored stimuli that triggered expected responses in the control group.

Investigators have found that nearly one third of children with autism have had temporal lobe epilepsy in infancy, and the percentage may be much higher given that many epileptic seizures go undetected. Caused by repeated random volleys of nerve impulses traversing the limbic system, the researchers theorize that these seizures could eventually scramble the connections between the visual cortex and the amygdala, indiscriminately enhancing some links and diminishing others. 

The Mirror Neuron and Salient Landscape theories for explaining the diverse symptoms of autism are likely to compliment each other. It is possible that the same event that distorts a child's connections between the limbic system and the rest of the brain--also damages the mirror neurons. Alternatively, the altered limbic connections could be a side-effect of the same genetic and/or environmental cause that trigger the dysfunctions in the mirror neuron system. 

In my assessment of these articles, the authors have some intriguing preliminary findings but they too quickly jump to making broad sweeping generalizations and assertions.  Undoubtedly, more detailed analysis of the brain through imaging will be required to more precisely determine the neurological pathways in autism and will eventually lead to improved treatment for autism.