Sub-second dopamine reinforcement shapes juvenile social play.

Sub-second nucleus accumbens dopamine is tightly linked to social syllables during naturalistic juvenile play, and Shank3 deficiency corrupts play-evoked dopamine differently in males versus females.

• Why it matters: Moment-to-moment neural reinforcement that organizes juvenile social interactions is unclear, limiting mechanistic targets for neurodevelopmental disorders with social deficits.
• What they did: The study used Social-seq 3D pose estimation with unsupervised clustering to quantify NAc dopamine coupling to sub-second play events, then tested Shank3-deficient autism models with multi-agent reinforcement learning and closed-loop VTA–NAc optogenetics.
• The result: In Shank3-deficient rats, proactive play dopamine responses were abolished in males and sign-inverted in females, and time-locked VTA–NAc stimulation restored reciprocal play, matching mutant phenotypes in the model.

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