So I have noticed there has ben a bit of a lag in this blog for a while, so I am going to open up this post as a forum for anyone who wants to ask their burning questions about pattern separation. On my part, I promise to come back often to make sure I can get any discussions going. Also, this is a prime opportunity to get experimental design advice and troubleshooting advice from the experts! Believe me, I have already used a few of these folks to guide my research!
So please, let the questions commence!
2 thoughts on “Questions and Answers”
OK so first I have to admit I haven’t been on here in a long time. Things have been busy. But I just realized that no one took you up on the “free answers for your questions” invitation. I would have jumped on that. That being said, I don’t consider myself an expert at all on these issues and do have a question that I hope you and others can help me think about. We talk about pattern separation as something that the hippocampus is really good at but it also happens outside of the hippocampus (for example in olfactory cortex, entorhinal, perirhinal, etc…) but if it’s so ubiquitous and happens pretty much anywhere there is any input/output transformation that decreases similarity… can we think of it as a function of the nervous system in general? I’m thinking about some of the data from the attention/perception world where they see thresholded discrimination functions in pretty much any hunk of cortex they test. Decision-making folks find the same thing and talk about it in terms of action selection… These functions seem like they’re popping up everything.. Is this simply how we can make sense of the world around us? And what makes the hippocampus special is the fact that it can access the most hyper dimensional input?
I think what makes the hippocampus is special is twofold. 1) Spatial pattern separation / completion. If the models are correct and the DG is involved in generating contextual representations, then it is really cool that the DG makes space and then orthogonalized it! 2) I think the hippocampus is involved mostly when one has to make flexible use of orthogonal representations to perform a task. That is, when there is a short term memory (or working memory in the Olton sense of the word) component to the task. For example, Ray Kesner just demonstrated that the ventral dentate gyrus is important for pattern separation for odors when (and only when) a 60 second delay is interposed. There is no DG requirement at a shorter delay of 15 seconds.
I do think the whole brain does work as a sort of pattern separator–it would be a sign of poor design id the brain were not designed to store vast amounts of information that were overlapping and not helpful for behavior (i.e., escaping predators, finding food, etc). That is why I am endlessly fascinated by the pattern completion processes in CA3…they seem to be the solution to a necessary problem with how the brain encodes information, meaning the tendency to over-orthogonalize.
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