Because leptin is released by fat cells, scientists think its presence in the blood is likely to signal to the brain that animals are in an environment where food is plentiful and there is no need to conserve energy. The new study shows that low levels of leptin alert the brain to the body’s malnourished state, thereby switching the brain into a low-power mode.
“These results are exceptionally satisfying,” said neuroscientist Julia Harris of the Francis Crick Institute in London. “It’s not uncommon to make beautiful discoveries that fit so well with existing understanding,”
An important implication of the new findings is that much of what we know about how the brain and neurons work may be learned from researchers who inadvertently put the brain into a low-power mode. It is very common to limit the amount of food available to mice and other laboratory animals before and during neuroscience research to motivate them to perform tasks in exchange for food rewards. (Otherwise, animals usually prefer to sit there.)
“One really profound effect is that it clearly shows that food restriction does affect brain function,” Rochefort said. She suggested that the observed changes in the flow of charged ions may be particularly important for learning and memory processes because they depend on specific changes occurring at synapses.
“If we want to ask questions about sensory sensitivity or neuronal sensitivity in animals, we have to think carefully about how we design our experiments and how we interpret them,” Glickfeld said.
The results also raise new questions about how other physiological states and hormonal signals affect the brain, and whether different levels of hormones in the blood can cause individuals to see the world slightly differently.
People vary in their leptin and overall metabolic profiles, notes neuroscientist Rune Nguyen Rasmussen of the University of Copenhagen. “So, does this mean that even our visual perception — even though we may not realize it — is actually different between humans?” he said.
Rasmussen cautioned that the question is provocative, with few hints of a definitive answer. Conscious visual perception in mice appears to be affected by food deprivation, as the neuronal representation of these perceptions and the animal’s behavior change. We couldn’t be sure, however, “because it would require animals to be able to describe to us their qualitative visual experience, which they obviously can’t do,” he said.
But so far, there’s also been no reason to think that the low-power patterns produced by neurons in the mouse visual cortex and their effects on perception wouldn’t be the same in humans and other mammals.
“These are mechanisms that I think are very important for neurons,” Glickfeld said.
Editor’s Note: Nathalie Rochefort is a board member of the Simons Initiative for the Developing Brain, funded by the Simons Foundation and is a This editorially independent magazine. Maria Geffen is Quanta.
ability Reprinted with permission Quanta Magazine, Editing independent publications Simmons Foundation Its mission is to enhance public understanding of science by covering research developments and trends in mathematics as well as the physical and life sciences.