Making memories

The picture above is of Professor Sir Gabriel Horn, speaking on mechanisms of memory, last Thursday evening. It was a talk I organised for my college's science society, before our annual dinner.

I'm currently the society president, which has been more work than I expected, but also great fun. The lead up to Thursday, for example, involved a cancellation, several different types of adaptor cables to connect a Mac to a projector, a last minute sign up, a seating plan, me having to write an introduction and talk in front of people, last minute placecards, finding a photographer - but on the night itself, everything went remarkably smoothly. Once we were sitting down for dinner, I could relax, and had really quite an interesting evening talking to Gabriel Horn about travel and epigenetics, amongst other things! We did slightly alienate the physicists sitting opposite, though - oops...



I've discovered that I actually really enjoy that kind of thing. The organising is a pain, but satisfying when it goes well. What I really like, though, is the opportunity to talk to people who do or have done awesome research, and to discuss science in quite a theoretical way, even if it's an area that neither of us knows a lot about. It also made me think that maybe I should be looking for PhDs in epigenetics, rather than in disease genetics, though, because it's fascinating, and we still don't know much. Like the brain!

And that, somewhat clumsily, brings me back to the topic of the talk, which was about the search for the mechanisms of memory. What changes in the brain when you meet someone new and file away their face and name for future reference? How does your brain access that information the next time you see them?

"In search of memory's trace: a voyage in the brain" was a review of Gabriel Horn's work done on imprinting in chicks. This is a much simpler system to observe changes in than looking at adult brains, which are already full of information and memories. The idea behind it is that chicks will "imprint" on the first thing they see after hatching. Usually, this is their mother. Imprinting enables them to recognise their mother, follow her, and be protected from other hens (who apparently sometimes kill chicks that aren't their own!). In this case, however, the chicks were hatched in darkness. The first thing they saw was a rotating red box. And they imprinted on it. Place it on a trolley and they would follow it around. Place them in a running wheel (like a hamster wheel!), and they would try to run towards it. Some chicks were shown a rotating blue cylinder instead, and each group would only recognise and follow the object they were first shown and had imprinted on.

Image from  the paper found here.

The investigators found that an increased proportion of neurons in a certain area of the brain, the IMHV/IMM (see figure above), responded to the red box / blue cylinder in chicks that had been imprinted on that object. If shown the other object, the proportion of neurons that responded was no higher than in untrained chicks. They also found increased protein synthesis in the brain after imprinting, suggesting something is growing or being made during the process of making a memory. In fact the structure of synapses was found to change, with the surface of the receiving cell becoming 'thicker', perhaps because of increased receptors.

Being a student, though, the part of the talk that I found most interesting was the part on sleep. Chicks that had six hours of rest after an imprinting 'training' session, then another session followed by six hours of disturbed rest, responded in the same way 20 hours after the first session as chicks that had been left to their own devices entirely. Both of these groups showed a high preference for the object they had imprinted on. In contrast, chicks which had six hours of disturbed rest after the first session, then another followed by six hours of undisturbed rest, showed much less of a preference for the object they had imprinted on.

The moral of this story? Have a nap after lectures! Or at least, don't stay up all night. Other studies have shown that taking naps can improve human memory. Gabriel Horn himself says that he always has a ten minute nap after lunch, even if the only place he can find is a lab bench, and it seems to have worked for him...

Why sleep helps, though, we don't yet know. I wonder, though, if it has something to do with the reallocation of resources during rest? Instead of energy being used for talking and walking around, it could be redirected to the brain to be used for protein synthesis and forming new connections to hold your new memories in place.

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References:


Some of Gabriel Horn's recent papers can be found here, although I haven't actually read them - this was based on my memory of his talk from the other night, which is hopefully accurate!