Invited Poster Session

3rd Biennial Conference on Brain Injury in Children | July 9-11, 2013 | Toronto, Canada


Accreditation, 3rd Biennial Conference on Brain Injury in Children | July 9-11, 2013 | Toronto, Canada


Fees for 3rd Biennial Conference on Brain Injury in Children , July 9-11, 2013 , Toronto, Canada

Sheena Josselyn, PhD

Senior Scientist, Program in Neurosciences & Mental Health, Canada Research Chair in Molecular and Cellular Cognition, EJLB Scholar Hospital for Sick Children, Associate Professor, Department of Psychology, Physiology, Institute of Medical Sciences University of Toronto

Making, Breaking and Linking Memories

Sheena Josselyn, PhD Senior Scientist, Neurosciences & Mental Health, Research Institute, SickKids; Associate Professor, Department of Physiology, University of Toronto; Canada Research Chair, Molecular and Cellular Cognition; Toronto, Canada

Executive Biography

Sheena Josselyn is a Senior Scientist in the Neuroscience and Mental Health department at the Hospital for Sick Children (SickKids) and an Associate Professor in the department of Psychology and Physiology and the Institute of Medical Sciences at the University of Toronto in Canada.  She is a Canada Research Chair in Molecular and Cellular Cognition and an EJLB Scholar.  Her undergraduate degrees and a Masters degree in Clinical Psychology were granted by Queen’s University in Canada.  Sheena received a PhD in Neuroscience/Psychology from the University of Toronto and conducted post-doctoral work with Mike Davis (Yale University) and Alcino Silva (UCLA).  Her program of research is dedicated to understanding the neural basis of cognitive function and dysfunction. To unravel the molecular, cellular and circuit processes that underlie learning and memory, her lab uses a multidisciplinary approach that focuses on mouse models and attempts to translate these basic findings into humans.

Presentation Abstract

A fundamental goal of neuroscience is to understand how information is encoded and stored in the brain.  The physical or functional representation of a memory (the memory trace or “engram”) is thought to be sparsely encoded over a distributed memory network. However, identifying the precise neurons which make up a memory trace has challenged for scientists since Karl Lashley’s “search for the engram” in the 1950’s (Lashley, 1950; Josselyn, 2010).  Moreover, it was not known why one neuron (rather than its neighbour) was involved in a given memory trace. We previously showed that lateral amygdala (LA) neurons with increased levels of the transcription factor CREB (cAMP/Ca++ Responsive Element Binding protein), are preferentially activated by fear memory expression, suggesting they are selectively recruited into the memory trace (Han et al., 2007).  We, and others, went on to show that these neurons were critical components of the memory network by selectively ablating (Han et al., 2009) or inactivating them (Zhou et al., 2009).  These findings established a causal link between a specific neuronal subpopulation and memory expression, thereby identifying critical neurons within the memory trace. Furthermore, these results suggest that at least within the LA, eligible neurons compete for inclusion in a memory trace, and that the winners of this competition are determined by relative CREB function.  Although competition between neurons, axons and synapses is necessary for refining neural circuits in development, little is known about competition between neurons in the adult brain. Our recent results suggest that this neuronal competition during memory formation limits the overall size of the memory trace (number of “winning” neurons) and is a mechanism that links (or disambiguates) related memories in the LA.

Memory impairments are a hallmark of aging, major mental illnesses (e.g., schizophrenia and depression) as well as neurological disorders (e.g., Alzheimer's and Parkinson's diseases). Therefore, understanding how the brain encodes and stores information is highly relevant to both mental health and mental illness.

Learning Objectives

  1. To broaden appreciation of mouse models of human memory processes.
  2. To increase understanding of neural mechanisms of memory formation.

Related Journal Articles

 Lashley, KS (1950). In search of the engram. Society of Experimental Biology Symposium, No. 4: Psychological Mechanisms in Animal Behavior. Cambridge: Cambridge University Press.

Josselyn, SA (2010) Continuing the search for the engram: examining the mechanism of fear memories. J Psychiatry Neurosci 35, 221-228.

Han JH, Kushner SA, Yiu AP, Cole CA, Matynia A, Brown RA, Neve R, Guzowski JF, Silva AJ & Josselyn SA (2007). Neuronal competition and selection during memory formation.  Science, 316, 457-460.

Han JH, Kushner SA, Yiu AP, Hsiang HL, Buch T, Waisman A, Bontempi B, Neve RL, Frankland PW & Josselyn SA (2009) Selective erasure of a fear memory.  Science, 323, 1492-1496.

Zhou, Y, Won J, Karlsson MG, Zhou M, Rogerson T, Balaji J, Neve R, Poirazi P, Silva AJ. (2009). CREB regulates excitability and the allocation of memory to subsets of neurons in the amygdala. Nat Neurosci 12, 1438-43.