Differentiation of memory operations along the hippocampal long axis

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Here I propose a cognitive neuroscience research program concerned with the distinct contributions of anterior hippocampus (aHPC) and posterior hippocampus (pHPC) to human cognition. The hippocampus is a brain structure with known importance for long-term memory, navigation, and other functions in humans and animals. In spite of its central importance in cognition, it is not known why, while internal circuitry of the hippocampus is organized in a similar fashion from front to back, only damage to pHPC impacts performance in most memory tests. In part because of this resistance to memory loss, intractable epileptic seizures, in which the hippocampus is implicated, are sometimes treated by removing aHPC but preserving much of pHPC. While aHPC does not predict the detailed memory typically measured in memory tests, my recent pilot data links it to a different, “fuzzy” memory that may be used to “zoom in” on detailed memories not otherwise accessible. People with larger aHPC appear to have better fuzzy memory, and those with larger pHPC better detail memory. aHPC also predicts traits and abilities in a variety of domains not traditionally associated with memory, such as vestibular processing, navigation, and even personality. To accommodate these varied relationships, I recently proposed an integrative theoretical model of hippocampal function linking, for the first time, the varied known functions of aHPC and pHPC with their distinctive physical compositions and neural connections. The predictions of this model, if confirmed, would greatly advance our understanding of fundamental principles of hippocampal operation. As this brain structure contributes to many domains, this advance would be influential to other researchers studying memory, navigation, emotion, sensation, personality, aging, and many other domains. The aims of the proposed research program address the nature of memory contributed by aHPC and pHPC; how these may underlie a wide variety of cognitive abilities and traits; what neuroanatomical features of aHPC and pHPC predict memory; and how aHPC and pHPC may interact in normal operation. Two graduate students will receive intensive computational cognitive neuroscience training in this program, incorporating learning of cutting-edge analytic techniques plus development of theoretical expertise. Thirteen undergraduate thesis students will also gain relevant exposure. Beyond theoretical advances, the work will characterize biomarkers of many traits and abilities in healthy adults. Better knowledge about aHPC and pHPC will also contribute to more informed decisions by epilepsy patients about whether to proceed with neurosurgery, as well as better anticipation of cognitive deficits in stroke patients, and aged or demented patients with hippocampal atrophy. This, in turn, will facilitate implementation of cognitive programs tailored to address these deficits.