Train your Muscles, Embiggen your Hippocampus

Mar 02 2011 Published by under Behavioral Neuro, Uncategorized

I want to start this post off with a video:

This is Mrs. Ida Keeling, a woman who has been breaking running records since she first started training at at 67. She's now 95 and America's oldest sprinter. And she is INSPIRING. I hope I'm just like her when I'm old, working out and strong (ok, I'll be a lot taller). She doesn't look or sound a day over 80. Not only is she physically fit, she's mentally sharp as a tack, and it really comes across in the interview.

Mrs. Keeling is a living example of this paper here, and what increased exercise may be able to do for the elderly.

Erikson, et al. "Exercise training increases size of hippocampus and improves memory" PNAS, 2011.

Yup, exercise is good for you, and it's even BETTER for you as you get older.

The hippocampus has been associated with a lot of things (on this blog I generally talk about the associated between changes in the birth of new neurons in the hippocampus and possibilities for depression), but its most well known for its role in things like learning and memory, the kind of memory forming ability that...decreases with age. A lot. This didn't used to be such a concern when the average human age was 35, but now that we are living so very much longer, the decreases in hippocampal volume (and functions related to it, like spatial memory) that go with age. People have been looking for drug therapies, but none have really emerged, and of course the potential problems of side effects remain an issue.

But what if staving off the effects of aging on the brain was as easy as exercise?

Well, I guess it depends on if you think exercise is easy.

For this study, the question was how exercise affected the volume of the hippocampus, markers of baby neurons being born, and spatial memory in the elderly. Exercise (wheel running) has already been shown before to increase neurogenesis (the birth of new neurons) in the hippocampus, and wheel running also increases measures of spatial memory in rats. But rats LOVE to run. They run a lot in general, and humans...well most humans do not. And most elderly humans CANNOT really go in for extensive exercise without danger of hurting themselves. It's time to move up to humans, and see if exercise works, and how much is enough.

So the authors of this study took 120 patients living in community style living, between the ages of 55 and 80. They all HAD to report being sedentary at the time of the study. They took 60 of them and told them to stay put, but gave them some stretching exercises with weights and resistance (so not exactly staying sedentary). They took the other 60 and put them on a supervised walking program, starting at 10 minutes a day and working up to 40 min a day, ending with the stretching and exercises that the other group got. It looks like the training sessions were every day (it doesn't say in the methods, boo, but they did chastise for low attendance), and they continued for a YEAR. The participants all had MRIs, blood levels, and spatial memory tests conducted at the beginning, 6 months in, and after a year. it's not an excessive amount of exercise, certainly they aren't making them run marathons.

And sure enough, the exercise made a difference.

The yellow there shows you the area of the hippocampus, and the lines with dots show you the before, middle, and after the exercise or non-exercise conditions. The results from the non-exercise (well, relatively little exercise) are depressing, showing a small drop in hippocampal volume (keep in mind it's only been a year). But the exercise group had a small INCREASE in hippocampal volume.

This increase was accompanied by increases in the amount of circulating brain-derived neurotrophic factor (BDNF), a factor most known for its hypothesized role in depression. But BDNF isn't just in the brain, it circulates in the blood. And increased levels of BDNF are associated with increases in baby neuron birth in your BRAIN. So they took blood samples for BDNF when they took the MRIs.

The correlations that you see here are only for the exercise group, and they showed a correlation between increase hippocampal volume and increase BDNF in the blood.

So increases in hippocampal volume and BDNF are all well and good, but what did it do to their BEHAVIOR? Did the people who exercised actually have better memory function?

Yes indeed they did! It's a small but significant improvement in spatial memory shown here for the exercise group. What's interesting is that there was actually improvement in the CONTROL group as well. They don't go into detail to explain why this might be, but it could be repeated exposure to the test, or that the stretching and wor that the control group did had an effect as well.

No matter what, the findings do look good for exercise, that it may be able to stave off the decline in hippocampal volume that is often seen in the elderly. This is probably taking place because exercise can increase cell proliferation in the hippocampus, "rescuing" the decrease in cell proliferation seen as you get old.

And while the findings aren't THAT striking (they are pretty small), they are a start. Certainly 40 minutes of walking a day isn't that much. Walking a dog three times a day for 15 minutes will more than get you there. The question now is whether more exercise is better, what NO exercise at all does, and how to adapt this to elderly individuals who might not be capable of doing longer distance walking. And while the effects are small, it doesn't look like it can hurt (as long as older individuals with balance issues are supervised to prevent falls and other injuries). And of course, what MORE is going on? Changes in hippocampal volume have been shown to affect depression scoring, did these people show changes in that? What about overall health? Other measures of brain function? Other brain areas?

But in the meantime until we have the answers, get walking (if health and abilities permit). Every little bit may help.

Erickson, K., Voss, M., Prakash, R., Basak, C., Szabo, A., Chaddock, L., Kim, J., Heo, S., Alves, H., White, S., Wojcicki, T., Mailey, E., Vieira, V., Martin, S., Pence, B., Woods, J., McAuley, E., & Kramer, A. (2011). Exercise training increases size of hippocampus and improves memory Proceedings of the National Academy of Sciences, 108 (7), 3017-3022 DOI: 10.1073/pnas.1015950108

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