NEUROANATOMICAL CORRELATES OF AGE-SENSITIVE AND AGE-INVARIANT COGNITIVE-ABILITIES - AN IN-VIVO MRI INVESTIGATION

The relationship between brain asymmetry and age-related differences i n cognitive abilities was examined in a sample of 29 healthy volunteer s (18 to 78 years old). The volumes and areas of cerebral hemispheres as well as several cortical and subcortical regions were estimated fro m magnetic resonance imaging (MRI) scans. Fluid and crystallized intel ligence were assessed by tests of nonverbal reasoning and vocabulary. The magnitude of leftward hemispheric volume asymmetry significantly a nd uniquely contributed to explaining the variance in both cognitive m easures. None of the indices of regional hemispheric asymmetry showed a similar pattern of associations with intelligence. Although total br ain size, and the size of dorsolateral prefrontal cortex positively co rrelated with fluid intelligence, they also correlated with age and he ad size, and did not add significantly to the fluid intelligence varia nce explained by age alone.