Using IQ Discrepancy Scores To Examine the Neural Correlates of Specific Cognitive Abilities

Abstract

The underlying neural determinants of general intelligence have been studied intensively, and seem to derive from the anatomical and functional characteristics of a frontoparietal network. Little is known, however, about the underlying neural correlates of domain-specific cognitive abilities, the other factors hypothesized to explain individual performance on intelligence tests. Previous preliminary studies have suggested that spatially distinct neural structures do not support domain-specific cognitive abilities. To test whether differences between abilities that affect performance on verbal and performance tasks derive instead from the morphological features of a single anatomical network, we assessed in two independent samples of healthy human participants (N ϭ 83 and N ϭ 58; age range, 5-57 years) the correlation of cortical thickness with the magnitude of the verbal intelligence quotient (VIQ)-performance intelligence quotient (PIQ) discrepancy. We operationalized the VIQ-PIQ discrepancy by regressing VIQ onto PIQ (VIQ-regressed-on-PIQ score), and by regressing PIQ onto VIQ (PIQ-regressed-on-VIQ score). In both samples, a progressively thinner cortical mantle in anterior and posterior regions bilaterally was associated with progressively greater (more positive) VIQ-regressed-on-PIQ scores. A progressively thicker cortical mantle in anterior and posterior regions bilaterally was associated with progressively greater (more positive) PIQ-regressed-on-VIQ scores. Variation in cortical thickness in these regions accounted for a large portion of the overall variance in magnitude of the VIQ-PIQ discrepancy. The degree of hemispheric asymmetry in cortical thickness accounted for a much smaller but statistically significant portion of variance in VIQ-PIQ discrepancy.

Prediction of brain maturity based on cortical thickness at different spatial resolutions

“…We understand that the interaction term for PIQ and VIQ captures disagreement (or similarity) between the two measures (PIQ and VIQ) in relation to the residuals, which in turn might complicate the interpretation of the regression analysis as the main effects become conditional effects. Nevertheless, we would like to point out that conditional effects of PIQ and VIQ have been studied in relation to cortical thickness, e.g., in Margolis et al (2013).…”

Cognitive specialization for verbal vs. spatial ability in men and women: Neural and behavioral correlates

“…All test scores were converted to z-scores; the mean of the four spatial test z-scores yielded a measure of spatial ability and the mean of the two verbal tests yielded a measure of verbal ability. Following the methods of Margolis et al (2013) we then created "pure" spatial and verbal measures through regression procedures. For each, we simply regressed one on the other and saved the residuals.…”

“…Karama and colleagues studied verbal and spatial reasoning in a large sample (N = 207) of children and adolescents, and found that after controlling for GCA neither skill was related to cortical thickness (Karama et al, 2011). Margolis et al studied a wide age range (5-57) of healthy individuals (N = 83) who had been given one of several versions of the Wechsler scales, yielding Verbal IQ (VIQ) and Performance IQ (PIQ) scores (Margolis et al, 2013). To remove variance associated with GCA, they analyzed VIQ-regressed on PIQ (pure verbal) and PIQ regressed on VIQ (pure spatial).…”

“…Following the methods of Karama et al (2011) and Margolis et al (2013)we focused on verbal ability, after controlling for spatial ability, and spatial ability, after controlling for verbal ability. We hypothesize that spatial ability, but not verbal ability, will be positively correlated with surface area.…”

A possible correlation between performance IQ, visuomotor adaptation ability and mu suppression

“…The intelligence quotient (IQ) tends to remain relatively stable across development (Deary and Whalley et al, 2000;McArdle and Ferrer-Caja et al, 2002) and the estimation of IQ by means of psychometric tests is an index of relative intelligence that measures how well an individual performs in a cognitive domain with respect to a reference group of the same age. Previously it has been used to correlate low-level sensory discriminations with intelligence (Melnick and Harrison et al, 2013), developmental cognitive abilities with task performance (Pangelinan and Zhang et al, 2011;Smits-Engelsman and Hill, 2012), and neural correlates of specific cognitive abilities (Margolis and Bansal et al, 2013). It is also suggested that the cognitive motor abilities and intelligence may share the same neural substrates (Jung and Yeo et al, 2000;Duncan, 2005;Stevens, 2009).…”