Temple et al (2003) published an fMRI study of 20 children with dyslexia who were scanned both before and after a computerised intervention (FastForword) designed to improve their language. The article in question was published in the Proceedings of the National Academy of Sciences, and at the time of writing has had 270 citations. I did a spot check of fifty of those citing articles to see if any had noted problems with the paper: only one of them did so.

The authors presented uncorrected whole brain activation data. This is not explicitly stated but can be deduced from the z-scores and p-values. Russell Poldrack, who happens to be one of the authors of this paper, has written eloquently on this subject: “…it is critical to employ accurate corrections for multiple tests, since a large number of voxels will generally be significant by chance if uncorrected statistics are used. .. The problem of multiple comparisons is well known but unfortunately many journals still allow publication of results based on uncorrected whole-brain statistics.” Conclusion 2 is based on uncorrected p-values and is not valid.

Dorothy notes four major problems with the study:

There was no dyslexic control group; thus, we don't know whether any improvements over time were specific to the treatment, or would have occurred with a control treatment or even without any treatment.

The brain imaging data were thresholded using an uncorrected threshold.

One of the main conclusions (the "normalization" of activation following training") is not supported by the necessary interaction statistic, but rather by a visual comparison of maps.

The correlation between changes in language scores and activation was reported for only one of the many measures, and it appeared to have been driven by outliers. Looking back at the paper, I see that Dorothy is absolutely right on each of these points. In defense of my coauthors, I would note that points 2-4 were basically standard practice in fMRI analysis 10 years ago (and still crop up fairly often today). Ironically, I raised two of of these issues in my recent paper for the special issue of Neuroimage celebrating the 20th anniversary of fMRI, in talking about the need for increased methodological rigor...