New paper: Linking memories (Rashid et al)

asimSome memories seem to naturally go together. For instance, if you think of an important experience in your life (exchanging your vows at the church, for example), you may also be likely to think about another experience that happened around that time (later on your friend drank too much wine at the reception).  These two memories seem to be somehow linked in your mind.  In a new study, our labs have figured out how memories how this might happen in the brain.

Our memories are thought to be represented in the brain by small collections of cells (neurons). In recent years, our labs have identified collections of neurons (or engrams) in the brain’s amygdala that store specific memories. But there are many thousands of neurons in the amygdala. How does the brain decide which collections of neurons encode a particular memory? Sheena’s lab found that the activity (or excitability) of neurons in the amygdala fluctuates, and only the neurons that are most excitable when an event occurs are likely to ‘grab’ the memory.

In the new paper, we take this one step further and ask how are memories for separate events linked in the brain. We find that after encoding a memory, these ‘engram’ cells remain active for a few hours before their excitability levels fall back in line with their neighbors. We show that if a second event occurs within this window (i.e., <6 hours), then the memory for that event is encoded in exactly the same collection of neurons as the first memory. These two memories have been encoded in the same population of cells and have become linked.

In contrast, if the second event occurs outside of this window (e.g., a day later) then these cells are no longer excitable, and the memory for that event is encoded in a different population of cells. These two memories are not linked.

We went onto to prove that a neuron’s excitability was the key factor determining whether two memories were linked or not. By artificially manipulating neuron excitability we could link two memories that would normally be encoded in separate populations of amygdala neurons. Conversely, they could separate two memories that would normally be encoded in the same population of neurons.

Asim Rashid (in Sheena’s lab) is the lead author on this work. His contributions to the lab selfie project are above, and his paper is available here.

Eurogenesis 2016

One of the best things about the adult neurogenesis field is that we meet about every 3 months. This time in Bordeaux. Huge thanks to Nora Abrous and Sophie Tronel for organizing a terrific meeting! Many more pictures from the meeting can be found hereeurogenesis

Poster presentation Axel style

At the meeting and then on the streets of Bordeaux.image

Commentary on Tsokas et al

In nearly two decades of work, neuroscientist Todd Sacktor has argued that the protein PKM-ζ regulates memory maintenance in rodents. However, 3 years ago two papers (here and here) showed that mice lacking PKM-ζ could remember normally, and severely undermined PKM-ζ’s status as preeminent memory molecule. In response to these papers, a new study by Sacktor’s group reveals that another isoform of the protein acts as backup when PKM-ζ is knocked out. We have written a commentary on this new chapter in the PKM-ζ controversy. NV

NYU Frontiers in Memory Research

Some pictures from last week’s NYU Frontiers in Memory meeting in Florence, featuring Mark Mayford and Cristina Alberini.nyu florence

Okay, Blue Jays!

The 2016 lab outing to the Rogers Centre. Sungmo in charge of the selfie.baseball 2016.jpg

CAN in the 6ix!

Our lab was well represented at this week’s Canadian Association for Neuroscience meeting in Toronto. Pictured at the opening night reception are (L to R): Frances, Valentina, Adam (@adam_rams), Lina (@lmntran), Emily, Alex (@Neurochatter), Colleen and Gisella (@InAnOther).CAN 2016

Bonny, MSc

Congratulations to Bonny who successfully defended her MSc thesis today! Selfie-ed here with her exam committee (PF, Junchul Kim, Zhengping Jia, Min Zhuo and Lu-Yang Wang).bonny

Kids Science day

Albert, Lina and Patrick from the J/F labs doing a great job teaching local highschoolers all about memory at Kids Science day at SickKids.science kids

Lab Selfie day 2016

The members of the frankland/josselyn lab:selifie 2016