A recent study published in Neuron reveals a selective “low-power” strategy in brains under stress.
As brain size has grown, the glucose required to power the organ has grown massively, making the mammalian response to hunger a key component of survival. Because the core functions of the brain are essential, any compromise in the energy budget of those functions is likely to have devastating effects.
But the exact energy conservation strategies of the hungry brain have remained unclear.
Now a study at the University of Edinburgh has uncovered an energy-saving strategy not unlike the low-power mode of a laptop when the battery runs low. Mice whose diet was reduced enough for them to lose 15% of their body weight showed a sizeable reduction in the energy-carrying molecule ATP, which is derived from glucose. But the reduction was not in the crucial core functions of the brain. Instead, budgeting was evident in the visual cortex. The mice could still see, but at a lower resolution—an effect measured by changes in performance on a difficult visual task.
“What you’re getting in this low-power mode is more of a low-resolution image of the world,” said lead researcher Zahid Padamsey in an interview with Quanta Magazine.
A 2016 study at the University of Michigan included a finding that at first seems contradictory—an uptick in neuronal activity of the visual cortex in hungry mice. But the increased acuity was only found when viewing images associated with food.
The Edinburgh study completes the picture: When hungry, it appears that the brain reduces overall visual acuity to save energy but keeps sharp the ability to replenish energy by finding food.