As people get older, the hippocampus shrinks in size leading to memory loss and possibly dementia. In an attempt to find a priceless way to decrease the rate of memory loss, the study found that regular aerobic exercise for a year increases the hippocampal volume by 2%, replacing about two years of lost memory, and improves spatial memory. The study also found that individuals who do aerobic exercises have increased levels of BDNF which is involved in neurogenesis and cell proliferation in the hippocampus, contributing to improved memory and increased size of the hippocampus.
The study consisted of 120 participants between the ages of 55 to 80 who had no history of neurology diseases and were cleared by their physicians to make sure they were able to participate. The people were split randomly into two groups: 60 participants as the aerobic walking group and the other 60 being the stretching control group. Before the participants began their training, baseline measurements were taken of aerobic fitness, MRI, blood, and memory. Aerobic fitness levels were measured by monitoring heart rate and oxygen intake of participants walking on a treadmill. After the initial baseline test, the aerobic exercise group started walking 10 minutes a week, adding 5 minutes each week until reaching 40 minutes at the seventh week. After the seventh week, the participants kept at 40 minutes till the end of the year. The participants wore heart monitors to ensure they were walking between 50-60% of the individual’s maximum heart rate for the first seven weeks and 60-75% for the rest.
The stretching control group attended classes that consisted of four exercise that improve balance and tone muscles, and the intensity increases as in the second and third weeks by including weights and more repetitions. These participants were told to attend class and take logs as much as they could, and they got monthly feedback.
Functional MRI of the Brain (FMRIB)’s images were collected to monitor changes in the volume of the hippocampus, thalamus, and caudate nucleus before the start of the study as the baseline, after the sixth month, and at the one year after completion of the study. The participants had blood drawn prior to the study and after completion of the study to measure serum BDNF levels. Memory was tested prior to the study, after 6 months, and after completion of the study by having the participants remember the location of black dots that would disappear. A red dot would then appear, and the participant would have to determine if the red dot was in the same location as a black dot or not.
The FMRIB found that those in the aerobic exercise group had an increase in volume in the left hippocampus by 2.12% while the stretching control group decreased by 1.40%, and the right hippocampus for the aerobic group increased by 1.97% while the stretching group showed a 1.43% decrease in volume. However, only change occurred in the anterior hippocampus and nothing changed in the posterior hippocampus because the anterior portion contains the cells responsible for attaining spatial memory.
The study found that the thalamus of the aerobic exercisers increased but insignificantly, and the caudate nucleus decreased in the stretching control group only, showing that changes due to exercise happened mainly in the anterior hippocampus. From the fitness test, the study showed that over the year, the greatest changes in fitness and improved oxygen levels correlated to the greatest changes in hippocampal volume, but not in the caudate nucleus or the thalamus. The exercise group also showed an increase in serum BDNF that controls cell proliferation in the dentate gyrus of the hippocampus, leading to increased hippocampal volume and memory function. The test used to assess spatial memory showed that participants with higher aerobic fitness levels had improved memory performances on the test, showing that increase in the hippocampal volume in the aerobic fitness group leads to improved spatial memory.
In class, we discussed the development of neurons and the need for neurotrophic factors in order for neurogenesis to occur. BDNF stands for brain-derived neurotrophic factor that helps in the proliferation of the neuronal cells in the anterior hippocampus increasing in volume when exercise induced. This article shows that neurogenesis can occur in adults. Before reading this article, I assumed that after the first couple years of life, neurons could change because of neuroplasticity, but neurogenesis could not occur. I now understand that neurogenesis can occur within the brain later in life if stimulated, which can have profound effects on spatial memory function. From class, I understand that neurotrophic factors increase the likelihood that a neuron will survive, but I did not understand the extent of effectiveness of neurotrophic factors on neuronal growth until reading the article that showed how an increase in the BDNF led to an increase in hippocampal volume, meaning the neurotrophic factors contributed to the development of neurons to increase the volume in the anterior hippocampus, leading to increased memory.
Based on the study, one question that remained unanswered was how exactly did exercise lead to an increase in BDNF? The study proved there is a correlation, but did not examine how the correlation came about. If the reason for the increase is found, neuroscientists could find a way to stimulate the production of BDNF in a more direct and swift manner in order to increase hippocampal volume and could potentially lead to an increase in spatial memory in individuals with memory deficit.