Shared activity across neurons depends on how they are connected

What is it about?

Neurons in the sensory cortex do not always respond consistently to repeated presentations of a sensory stimulus. This response variability can be correlated across multiple neurons. Cognitive processes like paying attention to something in the sensory environment can reduce the extent to which response variability is correlated across neurons - and this reduction in shared variability could be advantageous for the brain. We show here that correlated variability depends on whether and how neurons are connected to one another through synapses. Neurons wired together with excitatory synapses show less correlated variability generally and that correlated variability is reduced even further with attention. These findings help us understand how shared variability arises in the brain and how cognitive processes like attention can turn shared variability up or down.

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Photo by Harrison Leece on Unsplash

Photo by Harrison Leece on Unsplash

Why is it important?

This study provides significant new insight in two areas: 1) We demonstrate that shared response variability across neurons depends on whether and how those neurons are connected via synapses. This had never been studied explicitly before. 2) We demonstrate that paying attention strongly reduces shared variability among neurons connected via excitatory synapses, even more so than it reduces shared variability among unconnected, random pairings of neurons. Both of these insights help us understand where shared variability comes from and how the brain manages it in order to facilitate optimal encoding of sensory and cognitive information.

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