Neural mechanisms of navigation and spatial memory
Every few generations, a monarch butterfly performs an extraordinary behavioral feat by traveling up to thousands of miles to the same ancestral overwinter sanctuaries. This astonishing migration of a tiny butterfly highlights an extreme form of what animals perform at a local scale every day: spatial navigation through an environment. For more than a century, scientists have questioned how the brain represents and supports purposeful movement through external space. Even as early as 1874, Darwin hypothesized that animals may rely on the presence of an inertia based navigation system. However, it was the discovery in 2004 and 2005 of medial entorhinal grid cells that provided one of the biggest breakthroughs in understanding the neural basis of spatial representation (Fyhn et al., 2004; Hafting et al., 2005). Grid cells are neurons in rodents that fire in repeating spatial locations to form a hexagonal pattern of activity covering the entire environment. The strict periodicity of this pattern may enable a metric representation of the animal’s own location, similar to a longitude and latitude coordinate system (Hafting et al., 2005; McNaughton et al., 2006). Researchers from biology to mathematics have been fascinated by grid cells and their ability to maintain a rigid periodic spatial firing pattern despite frequent variation in the animal’s running speed and direction. I will present data on the elegant mathematical basis of grid features and experimental work on the mechanisms that may underlie the crystalline structure characteristic of grid cells.
Lisa Giocomo is an Assistant Professor of Neurobiology at Stanford University School of Medicine. As a PhD student at Boston University, she examined the electrophysiological properties of single neurons in regions of the brain associated with spatial memory and navigation. For her postdoctoral studies, she relocated to Norway and discovered a molecular mechanism for the scale at which grid cells represent the external spatial environment. As a new faculty member at Stanford University, her group aims to determine the molecular and cellular substrates underlying the organization in grid cell properties. She combines electrophysiology, genetic approaches, behavioral paradigms and computational modeling to unravel mechanisms underlying spatial memory and navigation. Her lab hopes that in the long term, their research will provide key insights into diseases that target memory processing, such as Alzheimer’s disease and depression.