Variability in brain activity is closely related to the relevance of sensory inputs to behavior

What is it about?

Brain cells respond slightly differently each time they see the same thing, and these little fluctuations are shared across cells. This "noise" has long been treated as a problem the brain should suppress. Studying activity across many brain areas and tasks, we found the opposite: the pattern of shared variability tracks exactly the information the animal is using to make its decision. What looks like noise is actually a window into how the brain flexibly picks out what matters.

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Photo by Nareeta Martin on Unsplash

Photo by Nareeta Martin on Unsplash

Why is it important?

For decades, neuroscientists have faced a puzzle: when animals perform well, the shared variability among sensory neurons reliably drops — yet theory says this variability could simply be ignored by the rest of the brain. So why is it so tightly linked to behavior? This work resolves the paradox. We show that the signal and the variability emerge from the same circuitry, so what looks like noise is actually a readout of the information guiding behavior.