The development of functional connectivity along the hippocampal long-axis in infants

We do not remember events experienced as infants. Infancy is a critical period of development for the memory system, yet we know little about the functional neural changes that occur during this time. In adults, hippocampal-neocortical coupling is needed to establish long-term memories, and differs along the anteroposterior axis. We investigated hippocampal-neocortical functional connectivity along the long-axis at rest in 212 infants. We found that functional differentiation of the anterior and posterior hippocampus occurs very early on (<6 months old). We also identified numerous cortical regions where connectivity with the hippocampus was changing with age. A clustering analysis revealed that anteroposterior hippocampal connectivity was changing with cortical regions associated with memory, but also with canonical networks associated with salience and attention. These findings raise the possibility that infantile amnesia is in part a disorder of immature functional interaction between memory, attention, and salience systems that engender memory formation in adults.