Individual differences in general intelligence correlate with brain function during nonreasoning tasks

Brain imaging can help identify the functional neuroanatomy of general intelligence, (i.e., "g") and indicate how brain areas salient to g relate to information processing. An important question is whether individual differences in g among subjects are related to brain function even when nonreasoning tasks are studied. If so, this would imply that individuals with high g scores may process information differently even when no reasoning or problem solving is required. To further investigate this, we administered the Raven's Advanced Progressive Matrices (RAPM) test, a strong correlate of g, to 22 normal subjects and then measured cerebral glucose metabolic activity with PET while the subjects viewed videos on two occasions, tasks with no inherent reasoning or problem solving. Individual RAPM scores were correlated with regional brain activity using statistical parametric mapping (SPM99) conjunction analysis to combine both video conditions. Results showed greater activation in specific posterior brain areas (left BA37/19) in high RAPM scorers (P=.02, corrected for multiple comparisons). Subsequent analyses revealed a high/low RAPM group difference in functional connectivity between left BA37/19 activity and the left anterior cingulate/medial frontal gyrus. These data provide evidence that individual differences in intelligence correlate to brain function even when the brain is engaged in nonreasoning tasks and suggest that high and low g subjects may preferentially activate different neural circuits, especially nonfrontal areas involved in information processing. (C) 2003 Elsevier Science Inc. All rights reserved.