The Vaccine Controversy, Autism, and the Cherry Picker Conundrum
There is a widespread belief that infants later diagnosed with autism had normal development during the first year of life and then experienced regression. This was marked by aloofness, lack of interest in social interaction, cessation of imitation and loss of previously acquired words. This pattern of apparently delayed onset of autism is seen in about one-fourth of children with autism. Many parents believe that some kind of environmental insult affected their children and some have blamed vaccines. MMR vaccine is given between 12 and 18 months of age, which is the age interval when autistic regression becomes apparent. The coincidence of timing and the mistaken belief that MMR vaccine contained mercury have implicated this vaccine as a cause of autism. The data showing a lack of association between MMR or thimerosal-containing vaccines and autism has been reviewed elsewhere on this site. However, apart from the data showing a lack of association of vaccines and the incidence of autism, there also is the question of the biological implausibility of a cause-and-effect relationship. Which brings up the cherry picker conundrum.
Autism is unique as a neurodevelopmental disorder. Autism is not associated with obvious or widespread brain pathology although subtle microscopic changes in certain brain regions have been described by Bauman and others. Despite the severe disability that has caused autistic disorder to be classified as one of the pervasive developmental disorders, many general aspects of brain function remain intact in autism. What is unique is that autism specifically targets the social cognition module. This is the brain system which brings together all the "minimodules" that are the basis for social interaction. These minimodules are each discrete subcircuits and include attention-sharing, monitoring gaze direction, reading facial expressions, verbal and nonverbal language, prosody of language, semantic nuances of language (such as sarcasm, irony, etc), empathy, imitation, and many other aspects of behavior that subserve an integrated system for establishing and maintaining relationships. The circuit plan of the social cognition module brings all of these together as a coherent functional unit. Despite the organizational coherence, the functionalities involved map to different brain regions. In other words, the social cognition module is distributed among multiple minimodules; that is, it has a multifocal topology.
The cherry picker conundrum
It is not biologically plausible that an insult attributed to a vaccine or some other "toxicant" can cause highly selective brain damage by only "cherry picking" the discrete functionalities for social cognition in widely-separated brain regions while sparing many other functions.
The implausibility of a postnatal "cherry picker" event does not preclude the possibility that environment plays a role. As discussed elsewhere, the effect of a putative environmental insult is unlikely to be a postnatal event. Rather, the event impacts during the first several weeks of fetal development when the basic "circuit plan" of the brain is laid down. This calls for a separate and more in-depth discussion of genes, mutations, nerve growth factors, and neural connectivity during the earliest stages of brain development in the embryo.
A final thought: There is now an overwhelming body of evidence against the hypothesis that vaccines cause autism. Sometimes the distinction between opinion and fact is blurred. The following quote is from an article in Science Times (The New York Times, September 30, 2003, p. D4) about Dr. Maria Spiropulu's research in particle physics at Fermilab in Batavia, Illinois:
"Everybody is entitled to their own opinions, but they’re not entitled to their own facts. The data is the data."
Maria Spiropulu, Ph.D.
|Return to main page| |Links to other autism resources|