The brain, largely known as “The Final Frontier of Science”, and how it ages is still a wildly exciting subject of study for the neuro-Lewis and Clarkes of our generation. Remarkable new experiments are being performed by researchers at John Hopkins University and the Center for the Neurobiology of Learning and Memory at the University of California, Irvine. Young and old volunteers come in and watch pictures flash before a screen as the scientists literally watch their brains.

Neuroscientists have already established with the use of brain scans that a substantial bit of the electrical activity and blood flow that is associated with memory processing happens in the dentate gyrus, an area within the hippocampus, known to be involved with learning and thinking.

Published in Proceedings of the National Academy of Sciences, their study involves use of advanced magnetic resonance imaging (MRI) machines to scan the dentate gyrus and various areas within the brains of the volunteers at the very moment of their attempting to form and store certain new memories.

This is how it was done: A series of pictures of everyday objects such as fruit, pianos, computers, and telephones were shown to the volunteers who wore head sensors. Each were asked to press a button to indicate whether each picture was typically found indoors or outside. They were not told to remember these images. Later, after being shown another set of images, the volunteers were asked if they remembered seeing the specific before, or if seemed similar to one they saw before, of if the picture was completely new to them while the research team kept track of neural activity throughout both tasks.

The results aren’t surprising. The young adults were adept at differentiating the images as to whether they were brand-new, already seen or similar but not the same as an earlier image–one example being that a baby grand piano is not the same as a full grand.
“There would be a lot of activity when young people saw either new or similar objects,” said Michael A. Yassa, an assistant professor of psychological and brain sciences at Johns Hopkins and lead author of the study.

The activity indicates that the young people’s brains were acquiring and filing the information of the new images as ‘New Images’, even when they were quite similar to images that they had seen from the first set. As for the older volunteers aged 60-80, they were less successful at pattern separation- the ability to differentiate between things that are quite similar. Their dentate gyri showed far less activity when they were shown a similar, not identical images. Apparently, their brains didn’t create a completely new memory to correspond to the similar images, so that the photo of the baby grand piano seemed no different than the photo of the full grand. This way, the baby grand piano would be described as an “old” image, when in fact, it was a new one. Make sense?

Dr. Yassa’s work suggests that aging blunts our ability to separate today’s parking spot from yesterday’s, from today’s breakfast from last week’s. There are many different ways to process memories but one of the more important for everyday functioning is pattern separation. “Otherwise [memories] can override one another and confuse things.” Part of the problem, Yassa believes, is structural.

A separate section of his experiments involved newly developed MRI scanning technology. With this he found that the dentate gyrus in the majority of the older volunteers were not linked as robustly to the rest of the brain as in young people, meaning that messages did not flow as efficiently from elsewhere in the brain to the dentate gyrus memory center and vice versa.

However, there’s hope. “Exercise is one of the things that might directly change this process,” says Dr. Yassa. From other experiments, exercise was found to jump-start neurogenesis, the creation of new brain cells, especially in the dentate gyrus, potentially improving that area’s health and functioning. This definitely was the case in rodents. The National Institute on Aging conducted an encouraging study in 2010 where mice that voluntarily ran on exercise wheels displayed an ‘enhanced’ ability to separate closely spaced squares on a display screen (the animal equivalent of pattern recognition), compared with sedentary mice. The active rodents also had far more new neurons in their dentate gyri than those that didn’t run.

Dr. Yassa is including measures of physical fitness and exercise history as part of his ongoing research and the results look promising, he says. “What I’d say for now is that you can’t go wrong by exercising,” he said. “We don’t know if it can reverse any damage if you already have memory slips. But there are indications that might slow or possibly prevent memory deterioration, if you begin exercising early enough.”

References:

Yassa, Michael A., Aaron T. Mattfeld, Shauna M. Stark, and Craig E. L. Stark. “Age-related Memory Deficits Linked to Circuit-specific Disruptions in the Hippocampus.” Proceedings of the National Academy of Sciences. The National Academy of Sciences, 9 May 2011. Web. 26 May 2011. http://www.pnas.org/content/early/2011/05/05/1101567108.