The brain is one of the most powerful and most metabolic organs in the body. These two attributes determine that the brain’s structure and function must continually adapt to changes in the body’s metabolic level in order to improve the animals’ chances of survival. Common changes include seasonal hibernation and migration and mating.
Dehnel phenomenon (Dehnel phenomenon) is the most surprising phenomenon among them. In the harsh winter environment, the shrew’s brain has undergone a change that makes the scientific community feel very surprised.
Robert Naumann, research fellow at the Institute of Brain Awareness and Brain Disease, Shenzhen Institute of High Technology, Chinese Academy of Sciences led a research group and together with scientists from Germany and Israel, conducted specialized research. Deep in the brain structure of the shrew Suncus etruscus.
This seasonal change in the animal’s brain explains the experimental phenomenon that nerve cells in the cerebral cortex are inhibited by tactile signals in winter.
The results of the research were recently published in the Proceedings of the National Academy of Sciences of the United States and selected for the cover page.
Found from the Mediterranean to Malaysia, the Suncus etruscus shrew has only a body length of 36mm – 53mm, excluding the tail. This is the world’s smallest mammal if measured by body weight, averaging only 1.8g.
Suncus etruscus is the smallest terrestrial mammal with a weight of only 2 grams, they are distributed mainly in the subtropical and temperate regions of Eurasia, from 10 to 40 degrees north latitude. Their small size has resulted in a high metabolic rate and inability to store energy like other animals.
In order to adapt to an active nighttime habitat, this shrew evolved to be able to hibernate during the day and form the Dehnel phenomenon in winter.
To explore the Dehnel phenomenon, the team used nuclear magnetic resonance, in situ hybridization and other technologies to track from general anatomy to the cellular level, from behavioral tracking to activity. cortical nerve cells and elucidate changes in the structure of their cortical neurons during winter and summer.
Team members have long tracked many of the brain structures of the shrew Suncus etruscus through the MRI and found that the cerebral cortex is the most important structure in the phenomenon. The cortex thickness of the shrew Suncus etruscus is about 10% lower in winter than in summer.
Due to the poor vision of the shrew Suncus etruscus, they mainly locate prey through its very sensitive beard. Preliminary research shows that the shrew Suncus etruscus are a master hunter, taking only a few hundred milliseconds to kill their prey after putting them in sight.
Based on the above phenomenon, the team focused their research on the somatosensory cortex of this mouse species. The team found that the fourth layer of nerve cells in the somatosensory cortex in this species has the highest need for energy metabolism, and will decrease by 28% in winter thickness, while the thickness of the layers. the other child has no significant change.
In the fourth layer of the cerebral cortex there is an intermediate nerve cell Parvalbumin (PV nerve cell), the main function of this type of nerve cell is to inhibit the activity of peripheral nerve cells. According to the process of staining brain slices, the number of PV neurons in the animal in winter will be less than in summer, which has provided supportive anatomical data for the study results.
This rat is constantly looking for food to keep its body warm. Once there is not enough food, it will be cold and hibernate, at which point the body temperature drops to about 12 degrees Celsius.
The response of nerve cells to tactile signals can be divided into three categories: activated, inhibited or unresponsive. Through experiments, the team continuously studied the rat’s beard and recorded the calcium signaling of cortical neurons as well as quantified the nerve’s response to tactile stimulation. .
By comparing the fall and winter experiments with those in the spring and summer, the team found that in winter, the shrew has multiple neurons activated by signaling. more tactile effect. It is in line with anatomical data showing that PV nerve cells increase in spring and summer. The proportion of intracellular neurons inhibited by tactile stimuli increases 2 to 3 times in autumn and winter.
When fully fed, this rat likes to hunt crickets and worms. But when food is scarce, they will hunt for beetles to alleviate their hunger.
This study filled the gaps in the study of seasonal variation in the nervous system of animals. Through long-term follow-up of individual individuals and year-over-year recording of the group animals, it reveals differences in the animal’s cerebral cortex at the cellular, physiological and anatomic levels. general.
At the same time, this long-term adaptive alteration of the nervous system can also be considered a manifestation of nerve endurance.