Autism and the blooming brain: My new column in Discover

By Carl Zimmer | March 6, 2012 2:59 pm

In my new column for Discover, I write about Eric Courchesne, a neuroscientist at the University of California at San Diego. Courchesne survived childhood polio, went on to become a champion gymnast, and then turned his attention to another nervous system disorder: autism. Courchesne is one of the first researchers to find anatomical differences in the brains of people with and without autism. He believes his findings point to autism’s beginnings before birth, and perhaps even to new ways to treat it. Check it out.

[Image: SFARI]

CATEGORIZED UNDER: Brains, Writing Elsewhere

Comments (5)

  1. Jim Johnson

    Excellent article. As usual.

  2. RA Jensen

    Far too many autism researchers make astonishing claims that they have discovered a single causal mechanism that explains all of autism. There is no single causal mechanism that is predictive of autism.
    There are studies that have questioned the association of macrocephaly with autism. Ghazuddian et al (1999) examined 20 children with autism and 20 children with ADHD only. Of the 20 children with autism, four had macrocephaly, which is 20%, consistent with the findings in most other studies. Of the 20 ADHD controls, five had macrocephaly or 25%. The four autistic children with macrocephaly all were hyperactive and impulsive suggesting the association of macrocephaly in autistic children is with co-occurring ADHD rather than being specific to autism.

    Furthermore twins studies have shown that macrocephaly can be present in an affected twin and an unaffected co-twin.

    Macrocephalus in the Courchesne study is a group average. Other groups confirm that macrocephalus is present in 16% of all autistic children, however microcephalus is also present in 15% of autistic children. Macrocephaly can be familial and can be present in in unaffected sibling or parent

    What about the six cases where autopsy data was available?
    In another article discussing Courchesne’s paper there was dissenting opinions about the meaning of the Courchesne paper and the quality of the autopsy specimens.:

    “I know that sample,” says Lange, who is on the advisory board of the Autism Tissue Program, which manages some of the samples in the study. “It’s of varying quality, from poor to acceptable.”
    Amaral questions the premise that most children with autism have large brains. In an unpublished imaging study of 180 children, including 114 with autism, aged 2 and 3 years, his team has found that only about ten percent have larger-than-normal brains. What’s more, some work suggests that about 15 percent of children with autism have abnormally small brains3
    Red flags have to raised any time an autism researcher makes a claim that he has discovered the mechanism that explains all of autism
    That does not render the Courchesne study meaningless at all. It is an interesting study and may have recognized one of hundreds of risk factors of small effect.

    [CZ: Thanks for your comment, and for these useful links.]

  3. RA Jensen

    A red flag should be raised whenever a researcher claims to have discovered a single causal mechanism that explains most cases of autism or claims a very narrow window in the timing of the disruption or brain development. Cerebral palsy has many causes, genetics factors and unfavorable events at delivery and infections that can occur prenatally or in the neonatal period. The CDC as part of their autism monitoring network identified all children in the network diagnosed with cerebral palsy. Of the 8 year olds diagnosed with cerebral palsy, 39 of the 439 (8%), had a diagnosis of cerebral palsy + autism. The prevalence rate of 8% is 8 times higher than the CDC’s published prevalence rate of 1/110.

    Twenty years Dr. Courchesne published another hypothesis, his ‘cerebellar’ hypothesis. Based on MRI studies and autopsy reports he hypothesized that autism was caused by massive losses of cerebellar Purkinje neurons and arrested development in the limbic system (there were too many cells and they were too small).

    It is becoming abundantly clear that studying autopsy brain tissue that targets only one area of the brain, the prefrontal cortex in this article and the cerebellum in other autopsy studies creates more confusion than clarity. Autopsy studies should always include studying the entire brain.

  4. As a parent and blogger I am a little suspect of researchers claiming to have discovered a single causal factor to autism. I have read so much research since my son was diagnosed claiming either genetics or environmental factors that its difficult to know who is right or if they are both right. I suspect autism is likely genetic but until we start unlocking some of its secrets its difficult to absolutely state either way. I just wish and pray that more money gets thrown at research and that we can start kicking some goals shortly because science aside, from a parents perspective there isnt much help at the moment.


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The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.

About Carl Zimmer

Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The LoomHe is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.


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