Effect of White Matter Lesions on Intelligence
Brain lesions have long been a topic of interest for neuroscientists,
dating in some way back to ancient peoples' practice of trephination,
in which holes
were created in the skull presumably to alleviate various symptoms and
problems. It is also hypothesized that
these holes were believed to grant the person special powers. Clearly,
in some manner, it has been understood that
changes to our heads and brains will produce changes in how our minds
A recent study by Bigler, et al (2003) investigated the roles of white
lesions, Cerebral Atrophy and apolipoprotein-E on cognition in the
elderly. This study used a large sample of the elderly
population of Cache County, Utah.
kind of white matter abnormality, seen as signal hypertensities on MR
scans increase in frequency with age. Although
it is widely understood that a reduction in white matter is correlated
with dementia and worsened cognitive processes, the role of white
lesions (WMLs) has been debated. There have been some studies that
the argument that Centrum Semiovale White Matter Lesions were the more
salient form of brian lesions with respect to intelligence, and some
argue for the importance of Peri-Ventricular White Matter Lesions.
In this, and another study (de Groot et al 2000, 2001) periventricular
matter lesions are correlated with impairment in cognitive tasks. The
study by Bigler et al (2003) used a
battery of CERAD neuropsychological exams, as developed by Welsh et al
(1994). Clinical dementia was also
evaluated, to create a distinction between the participants with
deficits and those without.
Magnetic Resonance Imaging was used as the exploratory procedure. The
researchers calculated total gray and
white matter volumes, hippocampal volumes, whole brain volumes,
ventricular volumes, and a total ventricle/brain ratio as an index of
atrophy corrected for brain size.
The main result of this study was a solidification of the finding that
periventricular white matter lesions are correlated to deficits in
function. PVWMLs were correlated with an r of
approximately .30 for almost all cognitive impairments, which included
immediate memory, delayed memory, visuospatial skills, language skills,
executive function, and a raw intelligence score.