Brains of scientists on a 14-month Antarctica expedition have shrunk, says study
According to the lead author of the study, social isolation and sensory deprivation, including the lack of navigation in large-scale space, could be the possible reasons, which contributed to the brain shrinking.
Faced with extreme environmental conditions and isolation, crew members of a polar expedition saw an area of their brains -- responsible for spatial thinking and memory -- shrink during their 14-month stay at an Antarctic research station.
On average, dentate gyrus, which is an area of the hippocampus, shrank by 7%, according to the research team from Charité - Universitätsmedizin Berlin and the Max Planck Institute for Human Development. Lead author Dr. Alexander Stahn of Charité's Institute of Physiology told MEA WorldWide (MEAWW) that this shrinking of the brain does have an adverse impact mentally.
"The higher the decreases in dentate gyrus volume, the smaller the improvements in tasks requiring spatial thinking and selective attention," Dr. Stahn, who is also an assistant professor at the Perelman School of Medicine, University of Pennsylvania, told MEAWW. According to him, social isolation and sensory deprivation, including the lack of navigation in large-scale space, could be the possible reasons, which contributed to the brain shrinking.
"What we see here is similar to various processes in the clinical setting and in the aging population. It seems that the extreme environmental conditions "accelerate" this change. In addition, social isolation is also of growing concern in many countries," Dr. Stahn explained. The nine polar expeditioners (five men and four women) lived in Antarctica at the Neumayer III station -- a German Antarctic research station run by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).
Living and working there meant they had to face temperatures as low as -50 degrees Celsius (-58 degrees Fahrenheit) and almost complete darkness during the winter months. According to the researchers, contact with the outside world is minimal, and cutting one's stay short is not an option -- at least not during the long winter months. Emergency evacuation and deliveries of food and equipment are only possible during the relatively short summer.
Accordingly, the study authors wanted to determine whether or not an Antarctic expedition produces changes to the structure and function of the human brain. "This scenario offers us the opportunity to study how exposure to extreme conditions affects the human brain," says Dr. Stahn.
The expeditioners, who were around 33 years old, volunteered to participate in the study. Of the 14 months spent at the research station, nine were spent in isolation from the outside world. They had to undergo cognitive tests before, during, and after their mission - which includes evaluations of memory, concentration, cognitive reaction time, and spatial thinking.
The authors say that regular blood tests were carried out to measure levels of a specific growth factor known as a brain-derived neurotrophic factor (BDNF), a protein responsible for promoting the growth of nerve cells and synapses in the brain. To record changes in brain volume -- paying particular attention to the hippocampus, which is located deep inside the brain -- the researchers used magnetic resonance imaging. The idea was to determine brain structure in each of the participants before and after their mission.
"For this, we used a high-resolution methodology which makes it possible to take precise measurements of individual areas of the hippocampus," says Dr. Simone Kühn, group Leader of the Lise Meitner Group for Environmental Neuroscience at the Max Planck Institute for Human Development. All the tests were also conducted on a group of nine control participants who did not stay at the station.
"Measurements taken after the end of the exhibition revealed that the dentate gyrus, an area of the hippocampus with an important role in spatial thinking and memory formation, was smaller in members of the expedition team than in controls. These changes were also associated with a decrease in BDNF levels. After only three months in the Antarctic, levels of the growth factor had decreased to levels below those recorded before the start of the expedition and had not returned to normal one-and-a-half months after the expedition," says the analysis.
According to the findings, published in the New England Journal of Medicine, cognition tests showed effects on both spatial abilities and the "so-called selective attention," which is necessary to ignore irrelevant information. Repeated testing is usually associated with improvements in test results. This learning effect, however, was reduced in participants whose dentate gyrus had decreased in volume, the reduction proportional to the extent of the volume lost, says the study.
"The reductions in dentate gyrus volume were also associated with lower cognitive performance in tests of spatial processing and selective attention," the findings state. Are these changes reversible? "I believe they are, but we have no data published on this yet," Dr. Stahn told MEAWW.
Taking forward their findings, the researchers are conducting another study. In this, they will analyze whether or not physical exercise might be able to counteract the observed changes in the brain.
Given the small number of participants, Dr. Stahn says the results should be viewed with caution. "They do, however, provide important information, namely - and this is supported by initial findings in mice - that extreme environmental conditions can have an adverse effect on the brain and, in particular, the production of new nerve cells in the hippocampal dentate gyrus," he said.