Eighteen gifted and 18 nongifted adolescents were analyzed. They solved reasoning problems, having high (complex) and low (simple) loadings on g. Increased bilateral frontoparietal activations (lateral prefrontal, anterior cingulate, and posterior parietal cortices) were found for both groups, but the gifted subjects showed greater activations Inhibitors,research,lifescience,medical in the posterior parietal cortex. Furthermore, activations in BAs 7 and 40 (superior and intraparietal
cortices) correlated with intelligence differences. Therefore, high intelligence was associated with increased involvement of the frontoparietal network through preferential activation of the posterior parietal regions. Gläscher et al28 investigated the neural substrates of g in 241 patients with focal brain damage, using voxel-based lesion-symptom mapping. Statistically significant associations between g and this website damage within a distributed
network in frontal and parietal brain regions were found. Further, damage of Inhibitors,research,lifescience,medical white matter association tracts in frontopolar areas was also shown to be associated with differences in g. They concluded Inhibitors,research,lifescience,medical that g draws on connections between regions integrating verbal, visuospatial, working memory, and executive processes. Going one step further, Gläscher et al28 asked whether or not there was a neural region whose damage uniquely impacts g beyond subtests contributing to the general score. They examined this question by analyzing the Inhibitors,research,lifescience,medical nonoverlap between a disjunction of subtests and the reported lesion pattern
for g. A single region was found in the left frontal pole (BA 10) showing a significant effect unique to g. This result complements the distributed nature of g and suggests a hierarchical control mechanism. This unique area for g may be involved in the allocation of the working memory resources necessary for successful performance on specific cognitive tasks. However, this finding should Inhibitors,research,lifescience,medical be placed within context since there are studies showing no decline in intelligence associated with prefrontal lobotomy, presumably including the frontopolar cortex.35 Therefore, future studies are necessary to determine the specific necessity of the frontal poles to g. The comparison between lesion cohorts and normal cohorts must be done carefully. The structural next studies reported by Colom et al27 and Karama et al50 are also consistent with the P-FIT model. In the first study (N =100) the general factor of intelligence was estimated after nine tests measuring reasoning, verbal, and nonverbal intelligence. Their VBM approach revealed several clusters of voxels correlating with individual differences in g scores. The main regions included the dorsolateral prefrontal cortex, Broca’s and Wernicke’s areas, the somatosensory association cortex, and the visual association cortex.