Dissociating memory processes in the developing brain: the role of hippocampal volume and cortical thickness in recall after minutes versus days.

Retention of information over extended time periods places special demands on the brain. The neural correlates of memory performance after a short delay of 30 min and a long delay of 1 week are likely partly different, but we do not know how structural maturation of the brain contributes to the differential development of these functions. This question was investigated in a sample of 107 children and adolescents aged 8-19 years. Measures used were structural magnetic resonance imaging and the Rey Complex Figure Test copy, organizational strategy, and 30-min and 1-week recall. While the amount of details copied and later recalled after both 30 min and 1 week increased with age, the relative saving over 1 week (1-week/30-min ratio score) did not increase with age. Thirty minutes recall performance was related to thinner left orbitofrontal cortex independently of age and organizational strategy measured during copy, possibly reflecting executive components of retrieval or encoding processes. In contrast, the 1-week/30-min ratio, likely reflecting consolidation of memory traces, was related to larger bilateral hippocampal volume. This indicates that differential developmental effects on memory for short and long periods of time are related to differentially developing brain structures.