Finding the cells that hold memories

Sheena Josselyn's research follows the physical traces of memory, with questions about trauma, dementia and the consequences of changing recollection. Published in Alumni Digest as verified reporting from the University of Toronto.

Sheena Josselyn's research follows the physical traces of memory, with questions about trauma, dementia and the consequences of changing recollection.

Alumni Digest editorial deskSeptember 18, 20263 min read

In the September issue

Campus

University of TorontoSt. George, Mississauga & Scarborough

Focus

Research & public discoveryIdeas

Outcome

Verified reportingSeptember 2026 issue

The context

Where the work begins

In 2009, Sheena Josselyn and collaborators reported that they had located and erased a specific fear memory by destroying the cells that stored it. The work helped establish how clusters of neurons, called engrams, carry memories. At SickKids and U of T, Josselyn has continued investigating how those clusters form and function.

The takeaway

What follows

Her lab's later work examined why traumatic memories can spread beyond their original setting. A 2025 paper linked stress to unusually large engrams and traced a mechanism involving cortisol. Josselyn hopes this research can inform future treatment, while recognizing the distance to clinical use and the ethical questions raised by altering painful memories.

Finding the cells that hold memories

Where the work begins

What follows

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