The latest research shows that viral and bacterial infections could have lasting legacies on cognition.
In a recent study, researchers found that people with higher levels of common infectious agents in their blood — including Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus and herpes simplex type 1 that causes cold sores — are more likely to have memory and cognitive problems than people with lower levels.
The researchers are not the first to make the connection. Other studies have linked infections and their effects on the body, such as inflammation, disruption of lipid production, and amyloid plaque build-up, with circulatory disorders such as heart disease and stroke. And these in turn have been linked to memory disorders like Alzheimer’s and dementia. Some studies even suggested that memory loss may be a result of the brain reacting to invading infections.
In the latest study, researchers analyzed the memory in 1,625 people around age 69, living in New York City. They compared the scores on these cognitive tests against blood samples from the participants that detected five common infections: Herpes simplex type 1 (oral) and type 2 (genital), cytomegalovirus, the bacteria responsible for causing pneumonia, and H. pylori, which is found in the digestive tract and has been linked to inflammation in gum disease and heart disease.
Participants who had higher levels of infections were at 25% higher risk of scoring low on a cognition test called the Mini-Mental State Examination, which tested for recall. The association was strongest among women, participants with lower education levels, those on Medicaid or without health insurance, and people who did not exercise regularly. “This observation provides some indirect evidence that the negative effects of chronic infection might be mitigated by beneficial behaviors such as physical activity, and evidence is accumulating that exercise has anti-inflammatory effects,” the authors write.
The researchers continued to test the memory of the participants every year for an average of eight years, but the infections were not linked to changes in memory and thinking skills as time went on. That could mean that the the infections had already altered the memory and cognition of the participants. “The damage [was] already done at the time of enrollment,” said study author Dr. Mira Katan of the Northern Manhattan Study at Columbia University Medical Center in New York and a member of the American Academy of Neurology in an email response to questions about the results. “Another explanation would be that our duration of follow-up may have been insufficient to detect a change.”
How could infections that the body essentially fights off leave such a lasting legacy on cognition? Although the scientists aren’t sure, they have some theories. It’s possible that chronic, or persistent infections from the pathogens are leading to an overall higher level of inflammation in the body, and over time, that damage can compromise the blood vessels in the brain that contribute to making memories. Or, the infectious agents could be directly causing cognitive decline.
If the link between viral and bacterial infections and memory loss disorders is confirmed with further research, it could reveal new ways of thinking about, and treating memory loss. A viral or bacterial agent that’s driving memory problems could lead to a bigger push for controlling such infections from a public health perspective, and focusing on new, antimicrobial approaches to treating disorders such as dementia or Alzheimer’s. In a corresponding editorial, Dr. Timo Strandberg of the department of medicine at the University of Helsinki, Finland and Dr. Allison Aiello, an associate professor of epidemiology at the University of Michigan School of Public Health write: “Undoubtedly, demonstrating that old-age cognitive disorders, including [Alzheimer's disease], are slowly progressing diseases of viral etiology would revolutionize the dementia research field (and be Nobel Prize worthy). However, great challenges remain.”
One of those is the fact that no study has established conclusively that pathogens can cause cognitive decline. But the latest findings suggest that infections, and the levels of inflammation, could potentially be used to better identify at-risk populations.
“While this association needs to be further studied, the results could lead to ways to identify people at risk of cognitive impairment and eventually lower that risk. For example, exercise and childhood vaccinations against viruses could decrease the risk for memory problems later in life,” said Katan in a statement.
New research suggests that elite athletes -- Olympic medalists in volleyball, for example -- perform better than the rest of us in yet another way. These athletes excel not only in their sport of choice but also in how fast their brains take in and respond to new information -- cognitive abilities that are important on and off the court.
The study, of 87 top-ranked Brazilian volleyball players (some of them medalists in the Beijing and London Olympics) and 67 of their nonathletic contemporaries, also found that being an athlete minimizes the performance differences that normally occur between women and men. Female athletes, the researchers found, were more like their male peers in the speed of their mental calculations and reaction times, while nonathletic females performed the same tasks more slowly than their male counterparts.
The study appears in the journal Frontiers in Psychology.
"I think we have learned that athletes are different from us in some ways," said University of Illinois psychology professor and Beckman Institute director Arthur Kramer, who led the study with graduate student Heloisa Alves.
"We found that athletes were generally able to inhibit behavior, to stop quickly when they had to, which is very important in sport and in daily life, " Kramer said. "They were also able to activate, to pick up information from a glance and to switch between tasks more quickly than nonathletes. I would say these were modest differences, but they were interesting differences nonetheless."
Overall, the athletes were faster at memory tests and tasks that required them to switch between tasks. They were quicker to notice things in their peripheral vision and to detect subtle changes in a scene. And in general, they were better able to accomplish tasks while ignoring confusing or irrelevant information.
Perhaps the most interesting discovery was that female athletes had significant cognitive advantages over their nonathletic counterparts, Kramer said, advantages that minimized the subtle speed differences between them and the men. The female athletes were faster than their nonathletic peers at detecting changes in a scene and could more quickly pick out relevant details from a distracting background. Their performance on these and the other tasks was on par with the male athletes, whereas nonathletic males consistently outperformed their female peers.
Nonathletes excelled at only one of the cognitive tests the researchers administered. In this test, called the stopping task, participants were asked to type a "Z" or "/" key as soon as they saw it on a computer screen -- unless they heard a tone shortly after the character appeared, in which case they were told to refrain from responding. Nonathletes tended to be faster in cases where the tone never sounded, while athletes were better at inhibiting their responses after hearing a tone.
The ability to inhibit a response is one marker of what brain researchers call "executive function," the capacity to control, plan and regulate one's behavior, Kramer said. While it has obvious advantages in sport, the ability to quickly inhibit an action also is useful in daily life, he said.
"One way to think about it is you're in your car and you're ready to start off at a light and you catch in your side vision a car or a bicyclist that you didn't see a second ago," he said. Being able to stop after having decided to go can be a lifesaver in that situation.
"So both facilitating and inhibiting behavior is important," he said.
Kramer said the athletes' slower performance on this one task might be the result of a strategic decision they had made to wait and see if the tone sounded before they committed to pressing a key.
"My bet is that the athletes were just learning to read the task a little better," he said. "So if I'm a little slower in going, I'll be a little better at stopping if I need to."
All in all, the new findings add to the evidence that those who spend years training on specific physical tasks tend to also have enhanced cognitive abilities, Kramer said.
"Our understanding is imperfect because we don't know whether these abilities in the athletes were 'born' or 'made,' " he said. "Perhaps people gravitate to these sports because they're good at both. Or perhaps it's the training that enhances their cognitive abilities as well as their physical ones. My intuition is that it's a little bit of both."
Researchers from Nanyang Technological University in Singapore recruited 75 men and women who were non-gamers to play five different games on their smartphones for an hour a day. Randomly assigned to groups, subjects played spatial memory games such as "Bejeweled," hidden object games such as "Hidden Expedition," or action games such as "Modern Combat: Sandstorm." After a month of game playing, the researchers found that subjects who played action games boosted their ability to track multiple objects in a short amount of time. Meanwhile, those who played spatial memory and hidden object games improved their performance on visual search tasks. Their results are published in the open access journal PLOS One. Another recent study from the University of Texas Medical Branch at Galveston in the US revealed that gaming high school and college students have better hand-eye coordination and control than medical residents when it comes to surgical simulations.
Gentle electrical zaps to the brain can accelerate learning and boost performance on a wide range of mental tasks, scientists have reported in recent years. But a new study suggests there may be a hidden price: Gains in one aspect of cognition may come with deficits in another.
Researchers who study transcranial electrical stimulation, which uses electrodes placed on the scalp, see it as a potentially promising way to enhance cognition in neurological patients, struggling students, and perhaps even ordinary people. Scientists have used it to speed up rehab in people whose speech or movement has been affected by a stroke, and DARPA has studied it as a way to accelerate learning in intelligence analysts or soldiers on the lookout for bad guys and bombs.
Until now, the papers coming out of this field have reported one good-news finding after another.
“This is the first paper to my knowledge to show a cost associated with the gains in cognitive function,” said neuropsychologist Rex Jung of the University of New Mexico, who was not associated with the study. “It’s a really nice demonstration.”
Cognitive neuroscientist Roi Cohen Kadosh of the University of Oxford, who led the study, has been investigating brain stimulation to boost mathematical abilities. He has applied for a patent on a brain stimulator he hopes could help math-challenged students get a better grip on the basics, or even help the mathematically inclined perform even better.
Cohen Kadosh and his colleague Teresa Iuculano investigated 19 volunteers as they learned a new numerical system by trial and error. The new system was based on arbitrary symbols: A cylinder represented the number five, for example, and a triangle represented the number nine. In several training sessions the volunteers viewed pairs of symbols on a computer screen and pressed a key to indicate which one represented a bigger quantity. At first they had to guess, but they eventually learned which symbols corresponded with which numbers.
All of the volunteers wore electrodes on their scalp during these training session. Some received mild electrical stimulation that targeted the posterior parietal cortex, an area implicated in previous studies of numerical cognition. Others received stimulation of the dorsolateral prefrontal cortex, an area involved in a wide range of functions, including learning and memory. A third group received sham stimulation that caused a slight tingling of the skin but no change in brain activity.
Those who had the parietal area involved in numerical cognition stimulated learned the new number system more quickly than those who got sham stimulation, the researchers report today in the Journal of Neuroscience. But at the end of the weeklong study their reaction times were slower when they had to put their newfound knowledge to use to solve a new task that they hadn’t seen during the training sessions. ”They had trouble accessing what they’d learned,” Cohen Kadosh said.
The volunteers who had the prefrontal area involved in learning and memory stimulated showed the opposite pattern. They were slower than the control group to learn the new numerical system, but they performed faster on the new test at the end of the experiment. The bottom line, says Cohen Kadosh, is that stimulating either brain region had both benefits and drawbacks. ”Just like with drugs, there seem to be side effects,” he said.
Going forward, Cohen Kadosh says, more work is needed on how to maximize the benefits and minimize the costs of electrical brain stimulation. He thinks the approach has promise, but only when it’s used strategically, by picking the right brain regions to target and stimulating them while a person is training on the skill they want to improve. ”I think it’s going to be useless unless you pair it with some type of cognitive training,” he said.
But that’s not stopping some people from giving it a try on their own. Although it should be obvious that DIY brain stimulation is a bad idea, both Jung and Cohen Kadosh say there seems to be growing interest in the general public in using it for cognitive enhancement.
“There are some do it yourself websites I’ve stumbled across that are pretty frightening,” Jung said. “People are definitely tinkering around with this in their garage.”
The new study suggests one way that could backfire. And that’s not all, said Jung. ”You can burn yourself if nothing else.”