Sheena Josselyn

Dr. Sheena Josselyn is a Senior Scientist in the Neurosciences & Mental Health program at The Hospital for Sick Children (SickKids) and a Professor in the Departments of Psychology and Physiology and the Institute of Medical Science at the University of Toronto. She holds a Tier 1 Canada Research Chair in the Circuit Basis of Memory. Her research seeks to understand how the brain encodes, stores, retrieves, and modifies memories, with a particular focus on memory engrams—the sparse neuronal ensembles that represent specific experiences. Josselyn’s laboratory pioneered the concept of neuronal allocation, demonstrating that neurons compete for inclusion in an engram and that relative excitability helps determine which neurons are recruited. Her work has established causal links between defined neuronal ensembles and memory expression, and has revealed principles governing memory linking, specificity, generalization, persistence, and updating. By integrating molecular, genetic, imaging, electrophysiological, and optogenetic approaches, her research connects cellular mechanisms with circuit function and behaviour. Josselyn completed her graduate training at the University of Toronto and postdoctoral fellowships at Yale University and the University of California, Los Angeles. She is a Fellow of the Royal Society of Canada, an elected Member of the U.S. National Academy of Medicine, and a Fellow of the American Association for the Advancement of Science. Her contributions have helped transform the engram from a theoretical construct into an experimentally accessible biological entity, providing a framework for understanding both normal memory and memory dysfunction in neuropsychiatric and neurological disorders. Her work continues to broaden this framework.

Faculty Appointment

Department of Psychology
Institute of Medical Science