Developmental differences in hippocampal long-axis contributions to memory precision.

Memory precision varies along the hippocampal long axis in the mature brain. Yet, little is known about how the development of long-axis functionality influences this precision. We characterized how children and adults engage the long axis to form precise memories. Children (7-9 years) and adults performed two tasks that encouraged an orientation to specific details versus general scene categories during encoding. After, they performed a recognition test with studied scenes and yoked lures. Adults had more precise memories than children in that they better discriminated studied scenes from lures. Yet, both groups showed memory benefits after orienting to specifics. Examining hippocampal engagement revealed that the two age groups relied on different subregions during specific encoding, with children recruiting the posterior third and adults the anterior third. Engagement was also differently related to memory quality. While the posterior third supported subsequent memory across age groups, both anterior and posterior thirds showed developmental differences in how they encouraged false memories-reflective of mnemonic breadth. Individual differences in the source of specific encoding along the long axis revealed that premature shifts towards an adult-like profile were disadvantageous to children's memory. Our results suggest as development unfolds, refinements to the functionality of the entire long axis supports memory imprecision.