Mammals forget some of their memories when they wake up from hibernation but new research shows that this isn’t the case for amphibians. A team of researchers has discovered that salamanders remember all previously created memories upon waking up from brumation, the cold-blooded version of hibernation. The details were just published in the journal Scientific Reports.
Torpor is a state that leads an animal to rest for a period of time while lowering their metabolic rate and decreasing their body temperature. This allows them to make it through times when there is little food available. An example of this is hibernation, a period of time when warm-blooded animals sleep for months, usually during winter. They live off whatever food they had consumed in advance and their metabolism slows down enough to allow them to stay in this state. Cold-blooded animals have an equivalent called brumation; the main difference is that they have to occasionally get water before going back to “sleep.” Previous studies have showed that when warm-blooded animals wake up from hibernation, they lose some of their memories—especially ones that were created right before they began to hibernate. However, no studies had been conducted on animals undergoing brumation.
Scientists from the University of Lincoln collaborated with other research teams to study the effects of brumation on memory retention. The team studied fire salamanders (Salamandra salamandra), a species of amphibian that is common throughout the United Kingdom. Fire salamanders enter brumation every year, making them ideal models for the study. The researchers had the salamanders learn a simple maze. Once the salamanders had the maze memorized, the team split them into two groups. One group was placed into brumation conditions for 100 days while the other group acted as a control.
Once the brumation group woke up, the team tested both groups with the same maze. Interestingly, all of the salamanders were able to solve the maze. The salamanders that had entered brumation retained the information just as well as the salamanders in the control group. This shows that brumation doesn’t appear to affect memory, even when the memories were formed right before the torpor period.
The team’s findings show that unlike mammals, amphibians don’t appear to lose their memories after waking up from a state of torpor. While hibernation causes warm-blooded animals to lose memories, cold-blooded creatures undergoing brumation retain the information. The team isn’t sure what causes this but differences in memory processing mechanisms might have affected the results. There also may be currently unknown differences between brumation and hibernation that lead to changes in memory retention.
Wilkinson et al. The effect of brumation on memory retention. Scientific Reports (2017).