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The University of Potsdam. Campus Am Neuen Palais. A bright 28°C. Today I’m going to be a test subject in a study on “the connection between movement and thinking” – and I’m quite curious to see what it’s about. For more than two hours, I concentrate on a number of tasks. Admittedly, I switch to power-saving mode during the last one: Whenever squares on a screen pop up in the same place for a second time, I have to – alternately – press a button or speak “yes” into a microphone. But that’s not all. While the squares are popping up, I hear sounds at three different frequencies. And here, too, my task is to indicate when a sound occurs for the second time in one ear by pressing the button or speaking into the microphone. As a test subject, I have to concentrate on two different but simultaneous phenomena – and decide whether to use my voice or my hand.
The German Research Foundation’s (DFG) priority program “Human performance under multiple cognitive task requirements: From basic mechanisms to optimized task scheduling” supports 22 projects in Germany. One of them has been ongoing at the University of Potsdam since October 2015: “Effects of modality mappings within working memory on postural control, associated neural correlates, and training-induced modulation of dual-task performance in old age”. The researchers work at the intersection of cognition and movement. “It is, thus, one of the partial projects doing truly interdisciplinary research,” says Christine Stelzel, Professor of Experimental Psychology at the International Psychoanalytic University in Berlin. At the University of Potsdam, she and psychologist Gesche Schauenburg, are conducting their study on the connection between postural control and thinking, which is the focus of the Potsdam DFG project.
In addition to experiments on cognition and balance, the experimental part of the study includes EEGs and MRIs to find out more about what influences postural control in older people in particular. “The number of falls increases enormously in those over 65,” the psychologist explains. The risk of falling is particularly high when older people do several things at the same time, that is, while multitasking. “With advancing age, abilities deteriorate at varying rates. Maintaining balance, mobility, and coordination require more attention than in younger years.” At the same time, working memory – associated with the prefrontal cortex at the front of the brain and particularly important for flexible action control – is more cognitively challenged.
Okay, so this one’s about fall prevention. At the beginning, balance plays no role in my tasks. I’m the first test subject of the day for the student doing the testing, who tests my hearing ability and then my vision, like an optician would. He skips the “Mini Mental State Test” that checks for signs of dementia. After all, this first test run looks at 18- to 30-year-old test subjects – as a reference group – before the actual study with the target group of 65-80 year olds begins. After a couple of exercises that remind me of geometry class, we step out into the corridor. Here, the student first measures my normal walking speed. He then asks me to count backwards by seven while walking; now I need about double the time for the same distance. This test points to the study’s objective: The researchers want to demonstrate that “dual tasks” are harder for older people – and to understand why this is the case.
So why do older people fall? The hypothesis is that because postural control requires more attention with advancing age, processing additional information is more difficult. If, for instance, an elderly person in a shopping center hears, “Please bring a shopping basket!” working memory has to decide how to react: verbally – by answering – or motorically – by grabbing a basket. This decision-making process is done by working memory. Researchers assume that balance in elderly people drops when faced with a cognitive task. This means multitasking is more challenging.
Next comes the test with sounds and squares: The researchers also assume that certain stimuli are more strongly correlated with certain reactions. So when hearing an auditory stimulus, it is comparatively easy for us to react verbally, whereas in the case of a visual stimulus we tend to react motorically. “It is much more difficult, however, to react manually to an auditory information and verbally to a visual one,” Stelzel says. Thus, responding verbally to the visual stimulus of a square with a “Yes” and motorically to a sound with the press of a button is particularly challenging. These are the very situations in which older people in particular lose their balance, Stelzel notes.
The University of Potsdam. Campus Am Neuen Palais. A rainy 17°C. Today, the electroencephalography recording will be taken. It takes two students 45 minutes to install an EEG cap on my head and set the electric voltage to below 5 kilo-ohms at each recording point. When I swallow, blink, or speak, I see the curves measuring the electrical activity in my brain deflect on the tablet PC in front of me. Then the test begins. I again have to react to squares and sounds by pushing a button or saying, “Yes”. In contrast to the first test series, I do this task first relaxed while seated, and then on a force plate in semi tandem position, with both feet touching and my left foot a little forward. For me, too, the task is to maintain my balance! While one student coordinates the tests on the desktop, the other observes my balance on the force plate. And the EEG records how my brain regulates these tasks. After some three hours of mind-body training, enough data has been collected.
“We know that the working brain of older people can also be trained,” Stelzel says. This is why the older participants stay after the study to train both their balancing and cognitive abilities. “Using the neuroscientific parameters recorded in the EEG and the MRI, we hope to be able to predict which cognitive tasks disrupt one’s balance,” the psychologist explains. While Stelzel analyzes the MRI scans, Gesche Schauenburg focuses on the EEG datasets. The force plate on which the test subjects stand continuously measures the force application point of both feet on the plate and records precisely when they sway. The researchers assume there is a correlation between swaying and the difficulty of the cognitive task. In fact, multitasking is not easy for anyone. Some even argue that, in principle, doing several things at once is impossible: Although one can perceive several stimuli, deciding on how to react to them requires interrupting a task – be it for only a very short time.
Berlin Center for Advanced Neuroimaging. Charité. A sunny 25°C. The last part of the study awaits me: In Berlin’s Charité Hospital I have to perform the tasks while in an MRI scanner. First, a staff member explains the procedure: I must not have any metal on or in my body, have to take off my shoes, and can press an emergency button if necessary. Claustrophobic people will certainly not feel well inside the scanner. I am not allowed to move my head –stabilized with two cushions – during the test. Above my head is a screen displaying the exercises. Stelzel and her colleague cannot hear me while I’m doing my tasks in the tomograph. Only during breaks can we communicate via an intercom. Because it’s very noisy inside the scanner, I’m given earplugs and sound-absorbing headphones. These are necessary, since my task is to recognize a “target sound” and a “target square” and confirm by pressing a button. Many sequences of the task follow, as I lie still in the scanner for 90 minutes. Outside again, my fingers are somewhat cold, my legs have fallen asleep, and my neck is a bit stiff. Otherwise I feel fine. As a farewell gift, I’m given an MRI scan of my brain.
“Functional MRI is a method that offers good spatial resolution,” Stelzel explains to me. “It shows oxygen consumption in the brain and, thus, activity changes in certain brain regions.” Specific regions demand a lot of oxygen during particularly difficult tasks. In contrast, EEG has a high temporal resolution and records electrical activity changes in milliseconds, so both methods are well suited to visualizing the difficulty of tasks. In addition, MRI indicates the connectivity between brain regions, thus making visible which regions cooperate during which tasks. The researchers ultimately hope to combine the two datasets for each test subject. It is conceivable that particularly difficult tasks lead to significant voltage swings (EEG) and high activity in certain brain regions (MRI) as well as more swaying on the force plate. Conclusions could, then, be drawn as to which cognitive tasks impair a person’s balance, and suitable forms of training (so-called “multitask balance training”) could be developed to ultimately reduce the risk of falling.
Through the DFG priority program “Human performance under multiple cognitive task requirements: From basic mechanisms to optimized task scheduling”, researchers at the University of Potsdam and the International Psychoanalytic University Berlin (IPU) have been researching the connection between thinking and posture control since autumn 2015. The project “Effects of modality mappings within working memory on postural control, associated neural correlates, and training-induced modulation of dual-task performance in old age” is intended to prevent falls in older age. It will initially run through 2018 under the oversight of Prof. Dr. Urs Granacher (Training and Movement Science), Prof. Dr. med. Dr. phil. Michael Rapp (Social and Preventive Medicine), and Dr. rer. nat. Stephan Heinzel (senior researcher at the chair of Social and Preventive Medicine).
Prof. Dr. Christine Stelzel studied psychology at Philipps-Universität Marburg and Humboldt-Universität zu Berlin. She is currently Professor of Experimental Psychology at the International Psychoanalytic University in Berlin and is working on the Potsdam DFG project.
International Psychoanalytic University Berlin gGmbH
Dipl. Psych. Gesche Schauenburg studied psychology at Universität Hamburg and is preparing her doctoral thesis at Freie Universität Berlin. She is currently a staff member at the chair of Training and Movement Science at the University of Potsdam and is working on the Potsdam DFG project.
Text: Jana Scholz
Translation: Monika Wilke
Published online by: Agnetha Lang
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Read this and other articles on research at the University of Potsdam in our research magazine Portal Wissen. https://www.uni-potsdam.de/en/explore-the-up/news-and-announcements/university-magazines/archive-portal-wissen.html