Reversed hierarchy in the brain for general and specific cognitive abilities: a morphometric analysis.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Psychometrics

Background:

• Intelligence is a complex construct involving a hierarchy of cognitive abilities.
• General intelligence (g) and specific abilities represent different facets of cognitive function.
• Understanding the neural basis of intelligence requires examining brain structure at various levels of cognitive organization.

Purpose of the Study:

• To investigate the relationship between gray matter morphometric indices and different levels of the intelligence hierarchy.
• To determine if the neural correlates of intelligence differ across specific tests, first-order factors, and the general factor (g).

Main Methods:

• Structural magnetic resonance imaging (MRI) was used to measure gray matter volume, cortical surface area, and cortical thickness.
• One hundred and four healthy young adults completed a comprehensive cognitive battery.
• Latent scores for intelligence factors and individual tests were computed and analyzed for their gray matter correlates.

Main Results:

• Gray matter correlates of intelligence showed significant variability at the individual test level.
• This variability substantially decreased when analyzing first-order cognitive factors and the general intelligence factor (g).
• Fewer gray matter clusters accounted for individual differences in performance as cognitive generality increased.

Conclusions:

• The findings support a reversed hierarchy in the brain's neural organization relative to cognitive abilities.
• Higher levels of cognitive generality (e.g., g) are associated with a more consolidated set of gray matter correlates.
• This suggests that broad intelligent performance relies on a smaller, more integrated neural network.