Northwestern breakthrough: Reversing memory loss in older adults with brain stimulation

Scientists at Northwestern University have published a new study in the American Academy of Neurology journal in which they used a technique called TMS (transcranial magnetic stimulation) to target the hippocampus, a complex structure embedded deep inside the brain. The hippocampus plays a major role in learning and memory. As people get older, the hippocampus atrophies (wastes away), leading to age-related memory decline. Most people experience memory problems with age, especially the ability to remember unrelated events, for example, where you left your glasses or your neighbor’s dog’s name. This type of arbitrary recall is frequently a problem for older adults. The hippocampus plays an important role in linking these memories. The study, which enrolled 16 individuals between the ages of 64 and 80, found it is possible to alter memory abilities in older adults with age-related memory decline using precise stimulation of the hippocampus. “Older people’s memory got better, up to the level that we could no longer tell them apart from younger people,” says lead investigator Joel Voss, associate professor at the Northwestern University Feinberg School of Medicine. This is the first time scientists have demonstrated the ability to specifically retrieve memory function in older adults using stimulation, or any method for that matter. The hippocampus is frequently atrophied and small in older adults. The group used fMRI (functional MRI), an imaging test that measures brain activity, to locate the hippocampus deep inside the brain. The researchers also located a spot in the parietal lobe of the brain just above the ear that communicates with the hippocampus to deliver stimuli. Transcranial magnetic stimulation cannot be used to stimulate the hippocampus directly because it is located deep inside the brain’s memory center. However, TMS, which is a noninvasive technique, can be used to stimulate the superficially located spot in the parietal lobe that is connected to the hippocampus. “We stimulated where brain activity is synchronized to the hippocampus, suggesting that these regions talk to each other,” says Aneesha Nilakantan, first author and neuroscience graduate student in the Northwestern laboratory. To establish a baseline, younger adults and older adults were given arbitrary memory tasks, such as pairing objects on a computer screen with a particular location. Younger adults got it right 55 percent of the time, whereas older adults had a success score of 40 percent. The team then treated the study participants with TMS for 20 minutes each on five consecutive days. Magnetic stimulation led to improved function in the regions of the brain responsible for memory, which are typically disrupted in old age, as evidenced by increased neural activity on functional MRI. One day after the final stimulation, the study participants repeated a similar memory test. The researchers found that following stimulation, the older adults scored at the same level as young adults and it was impossible to distinguish between them in terms of memory performance. A fake stimulation (placebo) was performed as control and this did not result in improved memory. The research team now plans to test this breakthrough in age-related memory decline in people with mild cognitive impairment with longer periods of stimulation. Mild cognitive impairment is the intermediate stage between expected decline due to normal aging and more serious decline due to dementia or Alzheimer’s. Voss and colleagues are unsure how long the effects of the brain stimulation last. The improvement in memory can potentially be maintained with more stimulation. TMS has been shown to help people with depression where treatment for five weeks can produce antidepressant effects lasting several months. The group plans a future study in which they will enroll individuals with age-related memory loss and stimulate the brain for a few weeks.