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Description: What was the name of your best friend in grade 1? What did you have for lunch the day before yesterday? We most often find that the older memory is still there but the more recent one is not, or is, at least, harder to recover. I have no doubt that you could come up with a subjective theory for why that works. You spent a LOT of time with your best friend, used their name a LOT and so that memory is stringer than the one related to whatever you had for lunch recently. However, what sort of theory/hypothesis would you come up with if you were asked to speculate as to how that memory effects plays out in your brain? What happens at the neuron level to make old memories sometime so much stronger than new memories? Oh, and while you are at it, think about how you would design an experiment with mice to test your hypothesis (so you can monitor their neuronal functioning closely and take advantage of the fact the 30 days is a LONG time in mouse years. Once you have your hypothesis and methods sorted out have a look through the article linked below that describes the work of one lab looking at these questions.

Source: How memories form and fade: Strong memories are encoded by teams of neurons working together in synchrony, Science News, ScienceDaily.

Date: August 23, 2019

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So, no surprises? Well of course not, we can look back to one of the earliest theories of memory, the engram theory, that suggested that memories are made up of neural circuits in the brain, except that when Carl Lashley went looking for them in the brains of rats he had taught to run a maze (had  them develop a memory circuit for the maze) he could not find them – the removal of no brain areas resulted in the rats forgetting the maze. What the research discussed in the article linked above suggests is that learning the maze when motivated by the resulting food reward lead to the rats consolidating their memory by mapping it over a large number of neurons making it harder to remove or for time to extinguish.

Questions for Discussion:

  1. Are the effects discussed in the article simply due to rote memorization?
  2. How do the researchers explain how the consolidation of robust long-term memories might be understood and does that make sense to you as a description of how neurons work?
  3. What, if any, are the implications of this line of research for the effects of aging on memory?

References (Read Further):

Walter G. Gonzalez, Hanwen Zhang, Anna Harutyunyan, Carlos Lois. Persistence of neuronal representations through time and damage in the hippocampus. Science, 2019: Vol. 365, Issue 6455, pp. 821-825 DOI: 10.1126/science.aav9199

Josselyn, S. A., Köhler, S., & Frankland, P. W. (2015). Finding the engram. Nature Reviews Neuroscience, 16(9), 521.

Hübener, M., & Bonhoeffer, T. (2010). Searching for engrams. Neuron, 67(3), 363-371.

Mumby, D. G., Gaskin, S., Glenn, M. J., Schramek, T. E., & Lehmann, H. (2002). Hippocampal damage and exploratory preferences in rats: memory for objects, places, and contexts. Learning & memory, 9(2), 49-57.

Bartsch, L. M., Loaiza, V. M., & Oberauer, K. (2019). Does limited working memory capacity underlie age differences in associative long-term memory?. Psychology and aging, 34(2), 268.