Bioethics Blogs

How Sleep Resets the Brain

Caption: Colorized 3D reconstruction of dendrites. Neurons receive input from other neurons through synapses, most of which are located along the dendrites on tiny projections called spines.
Credit: The Center for Sleep and Consciousness, University of Wisconsin-Madison School of Medicine

People spend about a third of their lives asleep. When we get too little shut-eye, it takes a toll on attention, learning and memory, not to mention our physical health. Virtually all animals with complex brains seem to have this same need for sleep. But exactly what is it about sleep that’s so essential?

Two NIH-funded studies in mice now offer a possible answer. The two research teams used entirely different approaches to reach the same conclusion: the brain’s neural connections grow stronger during waking hours, but scale back during snooze time. This sleep-related phenomenon apparently keeps neural circuits from overloading, ensuring that mice (and, quite likely humans) awaken with brains that are refreshed and ready to tackle new challenges.

The idea that sleep is required to keep the brain wiring sharp goes back more than a decade [1]. While a fair amount of evidence has emerged to support the hypothesis, its originators Chiara Cirelli and Giulio Tononi of the University of Wisconsin-Madison, set out in their new study to provide some of the first direct visual proof that it’s indeed the case.

As published in the journal Science, the researchers used a painstaking, cutting-edge imaging technique to capture high-resolution pictures of two areas of the mouse’s cerebral cortex, a part of the brain that coordinates incoming sensory and motor information [2].

The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.