Common shrews display a rare ability to shrink and subsequently regrow their brains in response to seasonal changes. This phenomenon, known as Dehnel’s phenomenon, enables these small mammals to adapt to harsh winter conditions by temporarily reducing brain volume, which researchers have now linked to significant water loss within brain cells.
A recent study conducted by scientists from the Max Planck Institute of Animal Behavior in Germany sheds light on this unique biological process. Using non-invasive magnetic resonance imaging (MRI), the team observed that common shrews can lose approximately nine percent of their brain volume over winter, only to regrow it in the summer months.
Cecilia Baldoni, a postdoctoral researcher and the study’s first author, explained, “The cells lost water during this shrinkage, but they did not die.” This finding is significant as it challenges the conventional understanding of brain cell behavior during periods of dehydration. Unlike most animals, which typically suffer cell damage and death from water loss, shrew cells not only survive but also proliferate.
The implications of this research extend beyond the natural world. According to John Nieland, an expert in human brain diseases at Aalborg University in Denmark, the mechanisms observed in shrews may provide insights into conditions such as Alzheimer’s and Parkinson’s disease. “The brain shrinkage observed in shrews closely mirrors what occurs in patients suffering from these diseases,” Nieland remarked.
Understanding the Mechanisms Behind Brain Flexibility
The study identified a specific protein, aquaporin 4, which plays a crucial role in regulating water movement in brain cells. This protein was found to be present in higher quantities in the shrews’ brains during the shrinkage phase, similar to patterns observed in diseased human brains. This connection suggests that understanding how shrews manage brain volume could illuminate potential pathways for treating human brain disorders.
Researchers utilized high-resolution MRI to track changes in the brains of wild common shrews captured in Germany during both summer and winter. The imaging technique allowed for real-time observation of brain changes without invasive procedures. “This method enabled us to see how individual brains transformed as they experienced seasonal shrinkage,” said Dominik von Elverfeldt, senior author from the University of Freiburg.
Despite the reduction in brain volume, shrews demonstrated remarkable adaptability. Baldoni noted that the brain’s neocortex and cerebellum, which are crucial for cognitive and motor functions, maintained a more stable water balance compared to other regions. “These areas are responsible for essential skills like memory and coordination,” she explained.
Potential Applications for Human Medicine
The ability of common shrews to reverse brain shrinkage raises intriguing questions for both ecologists and neurologists. “Understanding the physiological mechanisms behind this phenomenon could lead to new insights into how brain volume decline affects behavior,” Baldoni added.
Many neurological conditions in humans, including Multiple Sclerosis, Amyotrophic Lateral Sclerosis (ALS), and various dementias, involve a progressive loss of brain volume due to water loss. Unlike shrews, human brain volume reduction typically results in irreversible damage and impaired function. “Currently, there is no treatment capable of stopping or reversing this decline in humans,” Nieland stated.
As researchers delve deeper into the second phase of Dehnel’s phenomenon — the regrowth of brain tissue from winter to summer — they hope to uncover strategies that could potentially enable human brains to heal and regenerate. Nieland expressed enthusiasm for the research, stating, “The prospect of having a model animal that can offer insights into the treatment of currently incurable brain diseases is incredibly exciting.”
This groundbreaking study not only enhances our understanding of shrew biology but also opens new avenues for research into human health, illustrating the potential lessons that can be learned from the natural world.
