Sleep facilitates pattern separation through SK channel-mediated sparse coding.

The roles of sleep in priming the brain for associative learning remain unclear. Here, we report that acute sleep deprivation in Drosophila selectively impairs pattern separation-the ability to distinguish between similar stimuli-without affecting classical conditioning. This deficit correlates with disrupted sparse coding in the mushroom body, reflected by an increased number of active Kenyon cells and greater overlap in their odor representations. Electrophysiological analyses reveal that sleep loss enhances small conductance calcium-activated potassium (SK) channel-mediated afterhyperpolarization in GABAergic anterior paired lateral (APL) neurons, leading to reduced levels of feedback inhibition onto Kenyon cells and compromised sparse coding. Targeted knockdown of SK channels in APL neurons reduces their augmented afterhyperpolarization and rescues the pattern separation deficits caused by sleep deprivation. These findings identify a critical role for SK channels in inhibitory interneurons to enable sleep to preserve sparse and decorrelated neural representations, thereby supporting cognitive processes such as pattern separation.