Mirror neurons as an explanation for autism

This month’s Scientific American has a cover story on why differences in the ‘mirror neuron‘ system may explain the social difficulties in autism – and an extended preview is available online.

Mirror neurons are cells in the brain that are active both when a person is performing an action, or when they see someone else perform an action, and have been hypothesised to be involved in perceiving and comprehending others’ actions.

The preview is written by neuroscientists V.S. Ramachandran and Lindsay Oberman and introduces an extended article (not freely available online) that argues that people with autism may develop with a dysfunctional mirror neuron system, making them less able to make sense of social interactions.

This basic difficulty could then lead to the common autistic features such as abnormalities of language development, non-verbal communication, emotion recognition and understanding others’ intentions, which all rely on social interaction to develop fully.

‘Mirror neurons’ were first discovered in monkeys by Giacomo Rizzolatti, author of the extended article. However, the mirror neuron system is poorly understood in humans, despite some interesting findings in the research literature.

Ramachandran is currently one of the most enthusiastic ‘mirror neuron’ evangelists, going as far as saying “I predict that mirror neurons will do for psychology what DNA did for biology”.

One of the difficulties with this research, is that when compared on a task that involves understanding others’ actions in some way, people with autism tend to perform worse than a non-autistic comparison group.

This makes it difficult to say whether differences in performing the task are really due to differences in the mirror system, or whether it’s a more general problem, such as learning or perception difficulties.

Nevertheless, one recent study has provided some of the best evidence that mirror system differences may genuinely be present.

A team led by neuroscientist Dr Mirella Dapretto asked children with autism who had normal IQ scores to observe and imitate emotional expressions while in an fMRI brain-scanner.

They were compared to non-autistic children and the researchers found that both groups of children performed the task equally well.

Crucially, the children with autism did not show brain activity in an area of the frontal lobe called the pars opercularis – part of the ‘mirror neuron’ system.

This provides strong evidence of differences in the mirror neuron system in autism, although why this difference occurs is still a matter of debate.

For those wanting a good scientific review of the research in this area, a pdf of a recent paper by Vittorio Gallese, one of the co-authors of the extended Scientific American article, is available online.

Link to SciAm preview article ‘Broken Mirrors: A Theory of Autism’.
Link to abstract of Dapretto study.
Link to coverage of Dapretto study from BBC News.
pdf of Vittorio Gallese’s review on mirror neurons and autism.

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