An interview with Professor Sheena Josselyn, Neurosciences & Mental Health program at The Hospital for Sick Children (SickKids), conducted by April Cashin-Garbutt, MA (Cantab)
I think Lashley’s approach was right, he was just limited by the tools of the time. Now, we have the ability to be much more targeted, so we can look at the cells important in memory that are active during the training session.
From this modern Lashley experiment we were able to find where the engram is, or at least a key component of the engram. We found cells that are certainly necessary for memory retrieval
“Do we now understand why one neuron, rather than its neighbour, is involved in a given memory trace?
We understand a lot more than we used to and we know that in the area that I study, the lateral nucleus of the amygdala, most excitatory big neurons have the potential to participate in a memory, but those cells that are more active, or more excitable, right before the training event, seem to be more likely to be involved.
That’s one important distinction between them and we can manipulate it, so we can play off excitability, and activity, and bias whether a cell participates in an engram or not. But maybe that’s not the whole story as right now, we don’t know how this happens naturally.
So far our research has involved a lot of manipulation, for example, we can increase, or decrease more than physiologically normal cell activity. But endogenously, how does this process work? We’re still at the beginning stages of figuring this out.
Do you think competition between neurons could explain other brain functions?
We haven’t studied that, but I imagine competition is probably used for other things. In many areas, the brain uses sparse coding, so not every neuron is engaged, and representation are probably distributed across different brain regions.
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