Published in a peer-reviewed study, the findings suggest that structural brain changes during menstruation may not be limited to those regions associated with the cycle. Most of the research on the hormonal effect on the brain has been focused on neural communication during cognitive tasks, not on structural changes themselves. "Yet, very little is known about how these fluctuations alter the structural nodes and information highways of the human brain." The results showed that, as hormones fluctuate, gray and white matter volumes change too, as does the volume of cerebrospinal fluid. "Although we do not currently report functional consequences or correlates of structural brain changes, our findings may have implications for hormone-driven alterations in behavior and cognition," the researchers wrote.