Are smart brains really more efficient? A comparison of evidence from studies on fMRI activation and intrinsic connectivity

A prominent and widely-accepted view of intelligence holds that the brains of more intelligent people are more efficient. This talk reviews and compares empirical evidence for two different conceptualisations of efficiency in... [ view full abstract ]

A prominent and widely-accepted view of intelligence holds that the brains of more intelligent people are more efficient. This talk reviews and compares empirical evidence for two different conceptualisations of efficiency in association with intelligence: a) Efficiency as a characteristic of brain activation during cognitive demand (less task-related brain activation for a given level of cognitive performance) and b) efficiency as a characteristic of intrinsic brain network organisation in a task-free, so-called resting state of the brain (shorter paths from a given node to all other nodes in the brain network). Regarding a) the efficiency of brain activation during cognitive demand, a meta-analysis of 14 brain imaging studies yielded 6 brain regions showing a positive and 2 showing a negative association between intelligence and brain activation. In a separate study, we demonstrated that the interpretation of either type of association in terms of neural efficiency critically depends on the functional brain network under consideration (cognitive control versus default mode). Regarding b) the efficiency of network organisation, recent studies using graph analyses of intrinsic connectivity during resting state fMRI converge on the finding that there is no association between intelligence and global efficiency. Instead, in a recent study, we observed brain region-specific associations between intelligence and nodal efficiency. Just as for brain activation during cognitive demand, these associations between intelligence and connectivity in the task-free state were partly positive (anterior insula, dorsal anterior cingulate cortex) and partly negative (temporo-parietal junction area). Thus, intelligent brains were not characterised by generally shorter path lengths. Rather, some brain regions were functionally closer and others more remote to the rest of the network. In conclusion, the currently available data suggest that intelligent brains are not generally more efficient - neither with regard to task-related activation nor with regard to intrinsic network. The talk will discuss functional brain networks as a potential moderator of the relation between intelligence and brain measures of efficiency.