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Embryonic Brain Development and the Myth of 40 Days

Hang around anti-choice activists long enough (or let them hang out long enough around you), and you’ll hear one say something like this:

Brain waves have been recorded at 40 days on the Electroencephalogram.

The medium-form version of the claim goes something like this (see Our Lady of Mt. Carmel Parish):

40 days: Brain waves can be measured with an Electronencephalogram
(Today we declare someone to be legally dead when his brain waves cease. So if the end of brainwaves marks the legal end of life, perhaps the start of brainwaves should mark the legal start of life?)

Our commenter and the religious St. Carmel website are both cribbing off of this passage, which you can find cut and pasted with only minor variations on multiple websites and letters to the editors of small-town papers across the country:

Is he aware that the brain waves of a developing baby are recorded at 40 days gestation on the EEG? (H. Hamlin, “Life or Death by EEG.” Journal of the American Medical Association, Oct.12, 1964.) Brain function is reliably present on the EEG at eight weeks gestation. This is six weeks after conception. (J. Goldenring, “Development of the Fetal Brain,” New England Journal of Medicine, Aug. 26, 1982, 564.)

Looks good, doesn’t it? I mean, golly gee whizzikers, the text cites the American Medical Association and the New England Journal of Medicine with academic formatting and everything! The people who wrote the text of this claim depend on that. They depend on you to not look any further.

Unfortunately for the purveyors of this text, Margaret Sykes has done the work to look into the matter, digging not only into the Hamlin and Goldenring publications but also into the citations that Hamlin and Goldenring themselves make. Hamlin made a speech and Goldenring wrote a letter — neither is peer-reviewed and neither is a research paper. Neither Hamlin nor Goldenring cite research demonstrating that “Brain waves have been recorded at 40 days on the Electroencephalogram.”

Even if those “brain waves” were demonstrated to be present, that wouldn’t equal cognition. The current state of knowledge regarding fetal brain development indicates that higher-order cognitive development occurs quite late in gestation, and certainly nowhere near as far back as 40 days. According to the National Institutes of Health, the brain doesn’t even differentiate into as many as five separate areas until 6-7 weeks after conception. At 8 weeks after conception, the fetal brain spans less than a 1/4 inch across (Mayo Clinic). It is not until 30 weeks that the brain begins to develop grooves and indentations that we associate with a fully-cognitive brain.

The claim made by those who cite the Hamlin and Goldenring publications as if they were scientific research is inappropriate. It is unsubstantiated. It is a myth.

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