Brian Michael Schilder - US grants

The hippocampus is a brain structure that is critical for the storage and recall of long-term memory as well as spatial navigation. It is also one of the only brain structures that maintains the ability to generate new neurons throughout one's lifetime, a feature necessary for effective long-term memory. This project will investigate the origins of human memory by comparing the hippocampus of humans to those of our closest living non-human primate relatives at the levels of neuroanatomy, gene expression, and genetics. This research will provide novel insights into the neurobiological basis of certain human-specific memory-related abilities and the ecological factors that may have driven their emergence. Furthermore, this project will identify neurobiological targets that may render humans uniquely susceptible to certain neurological diseases and disorders known to affect the hippocampus (e.g., Alzheimer's disease, Autism spectrum disorder). Data from this project may inform further research and discoveries on human brain form and function. The project will support undergraduate mentoring and research experiences, and the investigators will engage in public science outreach to promote understanding of neuroscience, genetics and human evolution.

While the hippocampus is central to long-term memory in all mammals, only in humans is it known to additionally mediate episodic memory, the capacity to recall specific personal experiences and imagine future events. This may have first emerged in our hominin ancestors to meet the demands of increasingly challenging environments, expanded home ranges, and novel hunting/foraging strategies. Recent evidence suggests that the human whole-hippocampus has become evolutionarily specialized compared to those of other primates in terms of relative size, neuronal structure and distribution, and gene expression. However it is well known that the hippocampus is composed of molecularly and functionally distinct subfields. This project will therefore investigate the evolution of the hippocampus in humans and non-human primates in terms of neuroanatomy, gene expression, and genotype. Volumetric proportions of hippocampal subfields and degree of adult hippocampal neurogenesis will be estimated, and ecological variables will be correlated with neuroanatomical measures to test for neuroecological relationships. Whole-transcriptome gene expression data of hippocampal subfields will be generated and used to identify genes that are differentially expressed in humans. Protein-coding and regulatory regions of genes will be tested for positive selection.