If you’re interested in these questions, I’m recruiting a post-doc to join our team at the University of Illinois Urbana-Champaign! You may find the job posting here: mcb.illinois.edu/climerpostdoc

There’s a lot left to understand here. Why are so few neurons stable? What are the molecular and activity factors that are driving the increased excitability in the stable cells? What is the role of these changes in memory function? Why does drift seem to vary across brain regions and species?

So what drives drift? We looked closely at the neurons and found that a small group of them were stable. These stable neurons were more excitable than neighboring cells, making the fate of the cells predictable.

We then looked at sensory variability - controlling or varying the smells animals received each day. Again, drift persisted at the same rate - suggesting that subtle sensory variability that is not relevant to the task isn’t the driver of drift either.

We first looked at behavior - comparing similar to dissimilar speed profiles - and found that there was no difference in drift between these sets of data. Place cells drifted at the same rate in both sets of behavior, ruling out behavior as the driver of drift.

Representational drift is how neurons change information across time. It is controversial because stable memory is thought to be encoded by stable representations. It may be due to behavioral or sensory variability, so we looked at this in place cells using multisensory virtual reality.

This was a phenomenal team project, and I deeply respect and admire my co-authors. Daniel Oh will finish his PhD soon and Heydar Davoudi is on the faculty job market this fall.