Alexander Stahn of the Perelman School of Medicine led a study that found a volume decrease in the hippocampi of explorers who spent 14 months at a research station in Antarctica. “It was an average of about 7%, which is really big in terms of brain changes,” he said.
https://www.usnews.com/news/health-news/articles/2019-12-04/antarctic-study-shows-isolation-monotony-may-change-the-human-brain U.S. News & World Report