Friday, April 03, 2009

WAIS-III brain injury lession mapping research

Interesting 2006 WAIS-III brain injury lesion mapping study by Glascher et al. in Neuron.  I have some concerns about the interpretation of the results (see below), but see this as a neat study because of the large sample size for lesion-specific subjects (n=241) and the very interesting visual-graphic presentation of the results...esp. the grand summary figure in the discussion section.  Also, a supplementary report to the article is also available.

My concerns are related to the presence of construct irrelvant variance (when viewed from a CHC lense - and the results of CHC-based cross-battery studies) in some of the WAIS-III index scores used.  The Verbal Comprehension Index (VCI) is a good indicator of Gc.  Processing Speed (PSI) is a good index for Gs.  However, the Working Memory Index (WMI) is a mixed measure of Gsm (Digit Span and Letter-Number Sequencing) and Gq (see prior post about Arithmetic test Gq classification), and the Perceptual Organization Index (POI) is a mixed measure of Gv (Block Design and Picture Completion) and Gf (Matris Reasoning).  This suggests caution when trying to interpret the research findings from a CHC perspective.  However, I can see the practical and functional utility of knowing the relations between WAIS-III index scores, even if some are not the most valid CHC indicators, and possible brain lessions.

We need more research like this using more construct valid indicators of CHC abilities.


The Wechsler Adult Intelligence Scale (WAIS) assesses a wide range of cognitive abilities and impairments. Factor analyses have documented four underlying indices that jointly comprise intelligence as assessed with the WAIS: verbal comprehension (VCI), perceptual organization (POI), working memory (WMI), and processing speed (PSI). We used nonparametric voxel-based lesion-symptom mapping in 241 patients with focal brain damage to investigate their neural underpinnings. Statistically significant lesion-deficit relationships were found in left inferior frontal cortex for VCI, in left frontal and parietal cortex for WMI, and in right parietal cortex for POI. There was no reliable single localization for PSI. Statistical power maps and cross-validation analyses quantified specificity and sensitivity of the index scores in predicting lesion locations. Our findings provide comprehensive lesion maps of intelligence factors, and make specific recommendations for interpretation and application of the WAIS to the study of intelligence in health and disease.
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