Remote spatial memory processing in the juvenile brain and contribution of the hippocampus

Abstract

A majority of research into memory formation and consolidation is commonly focused on adult brains and organisms. Our work focuses on the mechanisms of memory within the developing, juvenile brain in an attempt to provide a more full understanding of the underlying neural mechanisms of memory formation, consolidation and storage. During juvenile development, the brain undergoes important remodeling and synaptic pruning towards shaping the adult brain. Thus, during this time, memories may be lost through the remodeling of hippocampal-neocortical connections. The significance of comparing juvenile and adult memory processes is critical in understanding the structural changes that occur within memory-specific circuits associated with long-term memory formation. To provide a comparison of the neurobehavioral aspects of long-term memory formation in juveniles and adults, we trained Long Evan’s rats on a spatial task on postnatal days 16, 18, 20, 25, 30 or 50 (adults). Each age group was then tested for memory recall 24 hours or 3 weeks later. We noted that memory recall showed a dramatic change at postnatal day 20 such that memory recall at postnatal day 25 was similar to adult levels. We then used immunohistochemistry to quantify and analyze neural activity patterns in brain regions thought to underlie the short- and long-term storage of spatial memories. Identification of these regional activity changes during juvenile periods and comparison with adults allows us to explore the function and organization of interacting brain regions in long-term spatial memory storage during development.