Making Memories

Memories – both those we remember fondly and those we wish we could forget – are the focus of Professor Sheena Josselyn’s research. Josselyn, who is appointed to the Department of Physiology and Senior Scientist at The Hospital for Sick Children (SickKids), investigates how the brain collects, encodes, stores and retrieves memories. In a recent paper in the journal Science, Josselyn showed how researchers in her lab and the lab of her husband and fellow neuroscientist Professor Paul Frankland could eliminate bad memories from mice. She spoke with Faculty of Medicine writer Liam Mitchell about these results and their consequences.

Your research sounds like a scene out of Eternal Sunshine of the Spotless Mind, where the main characters have memories of each other removed. Was that the inspiration for your work?

To be honest, I’ve never seen that movie. What sparked my interest was a desire to understand the most complex and fascinating organ we have: our brains. I wanted to discover how our brains gather, store and retrieve memories. What I’ve found is that something my mother would say – that we only use 10 per cent of our brain – is wrong, but also kind of right. It turns out it only take a small amount of brain cells to form and retain a memory, but there are all of these other cells that end up getting clustered around them. Each cluster represents a memory and we hold and access these clusters separately.

How did you discover that?

We train mice to react to certain stimuli, like a sound. That creates a memory. Then, using a genetic trick, we’re able to stimulate that group of neurons. That triggers the memory and allows us to identify the cluster that contains it.

Now that you can isolate specific memories at the cellular-level, what does that allow you to do with them?

That’s what makes this research so fascinating. It has the potential to apply to a broad range of conditions – from Alzheimer’s and dementia to schizophrenia and depression.

In the case of our most recent paper, we were able to kill a specific cluster of cells, specifically ones containing a fearful memory. Once we did that, the mice no longer showed signs of fear when they encounter a stimulus that previously scared them. That provides a proof of concept that our understanding of how memories are formed is true. Now, we’re starting to do research on how we might be able to strengthen memories, which could have implications for how we can improve memories.

This could open up big ethical implications. Have you considered those?

Absolutely. The ethical considerations are huge, and I am certainly not advocating a future where we could perform plastic surgery on our memories. However, I am thinking of individuals who find themselves unable to participate in society, such as those who suffer PTSD, because they are haunted by specific memories. Could we allow them to live fuller lives by removing that memory? That might be a possibility in the future because of this research.