Effects of structural and functional prefrontal cortex maturation on verbal memory development

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The prefrontal cortex, including core regions of our mnemonic system, is characterized by protracted structural and functional maturation from late childhood into early adulthood. We hypothesize that this relatively late maturation contributes to the steep increases in verbal memory performance observed during adolescence. To test this, we compared verbal memory scores of children (10-12 years old), adolescents (18 year old) and adults (25-32 years old). As a measure of structural maturation, we investigated whether cortical thickness of the left inferior frontal gyrus (LIFG, important for verbal memory encoding) mediates the effect of age on verbal memory performance. Furthermore, we investigated whether a developmental increase in specialization (i.e. lateralization) of functional connectivity between the IFG and the left medial temporal lobe mediates the effect of age on verbal memory performance. Firstly, our results show increased verbal memory performance and leftward lateralization of functional connectivity, and decreased cortical thickness with age. More importantly, our results show that LIFG cortical thickness does, but LIFG functional specialization does not significantly mediate the increase in verbal memory performance with age. This indicates that structural maturation is indeed an important contributor to verbal memory development during adolescence, whereas functional LIFG specialization seems to play a less significant role.
Faculteit der Sociale Wetenschappen