Having a good sense of direction is a point of pride for most people. It’s embedded in our culture: real men never ask directions. They might drive the family minivan several dozen meandering miles through inner-city wherever, but they don’t need directions, honey, so just drop it.
A recent study at Johns Hopkins University and the University of Nebraska-Lincoln may have just provided a convenient excuse for those proud fathers and other individuals who struggle to remember how they got to where they’re standing. The study discovered that a virus of algae – called Chlorovirus ATCV-1 – can infect humans and impair their capacity for spatial reasoning and navigation.
The paper detailing the findings was published online in the Proceedings of the National Academy of Sciences (PNAS) on Oct. 27. The lead author of the paper is James Van Etten of the University of Nebraska-Lincoln Plant Pathology Department. Etten helped discover and characterize Chlorovirus ATCV-1 more than thirty years ago.
Etten discussed his findings in a release from the University of Nebraska. “Chloroviruses are worldwide,” he explained, “they’re very common among inland bodies of fresh water such as lakes and ponds.”
Chloroviruses are considered nonhuman viruses and are commonly found infecting algae in aquatic environments. Conventional virology holds that algal viruses don’t infect humans, but Etten’s paper found Chlorovirus ATCV-1 to be a possible exception.
The researchers were taking throat swabs from participants in a separate cognitive functioning study when they unexpectedly found chlorovirus DNA. They ended up finding evidence of chlorovirus infection in 43 percent of their participants. According to the PNAS paper, testing positive for chlorovirus DNA “was associated with a modest but statistically significant decrease in the performance on cognitive assessments of visual processing and visual motor speed.”
It’s always questionable to draw a quick causal link between two factors just because they appear to be correlated, so the Nebraska research team designed a mouse trial to attempt to validate their findings. In the follow-up experiment, infected mice were run through a maze and their results were compared to those of chlorovirus-free mice.
“The inoculation of ATCV-1 into the intestinal tract of nine 11-week-old mice,” reads the PNAS study, “resulted in a subsequent decrease in performance in several cognitive domains, including ones involving recognition memory and sensory-motor gating.”
Having firmed up the link between the chlorovirus and the cognitive deficits, the researchers then focused their efforts on genetic analysis. In order to determine which genes the virus was tinkering with, gene expression in a portion of the brain called the hippocampus was monitored. According to the PNAS paper, the hippocampus was chosen because it “contains pathways essential for learning, memory and behavior.”
The analysis indicated that ATCV-1 infection was “associated with a significant up-regulation or down-regulation of 1,285 individual genes.” These genes, according to the researchers, could be constructed into 34 different cognitive pathways related to diverse functions including visual processing, dopamine signaling and immune function.
“This is a striking example showing that the ‘innocuous’ microorganisms we carry can affect behavior and cognition,” said lead investigator Robert Yolken in the University of Nebraska release.
Much has been made of late concerning the human microbiome, which is the multitude of bacterial species that live on and within healthy humans. While there has been a big research effort to illuminate how our bacterial passengers interact with our bodies, there has been comparatively little research into the relationship between the “human virome” and the host. The effects of Chlorovirus ATCV-1 on human cognition are a striking example of how intriguing, subtle and unexpected some of those interactions may be.
