White matter hyperintensities and working memory: an explorative study.

White matter hyperintensities (WMH) are commonly observed in elderly people and may have the most profound effect on executive functions, including working memory. Surprisingly, the Digit Span backward, a frequently employed working memory task, reveals no association with WMH. In the present study, it was investigated whether more detailed analyses of WMH variables and study sample selection are important when establishing a possible relationship between the Digit Span backward and WMH. To accomplish this, the Digit Span backward and additional working memory tests, WMH subscores, and cardiovascular risk factors were examined. The results revealed that performance on the Digit Span backward test is unrelated to WMH, whereas a relationship between other working memory tests and WMH was confirmed. Furthermore, a division between several white matter regions seems important; hyperintensities in the frontal deep white matter regions were the strongest predictor of working memory performance.