Spontaneous behaviour is structured by reinforcement without explicit reward

. However, the neural mechanisms that guide the composition of naturalistic, self-motivated behaviour remain unknown. Here we show that dopamine systematically fluctuates in the dorsolateral striatum (DLS) as mice spontaneously express sub-second behavioural modules, despite the absence of task structure, sensory cues or exogenous reward. Photometric recordings and calibrated closed-loop optogenetic manipulations during open field behaviour demonstrate that DLS dopamine fluctuations increase sequence variation over seconds, reinforce the use of associated behavioural modules over minutes, and modulate the vigour with which modules are expressed, without directly influencing movement initiation or…

• BW
  Burroughs Wellcome Fund
• AP
  Alfred P. Sloan Foundation
• BR
  Brain Research Foundation
• JC
  Jane Coffin Childs Memorial Fund for Medical Research
• NI
  National Institutes of Health

  Awards: RF1AG073625, F31NS113385, R01NS114020, U19NS113201, NS072030, F31NS122155
• NE
  National Eye Institute

  Award: EY012196
• NI
  National Institute of Neurological Disorders and Stroke

  Awards: U19NS113201, R01NS114020, NS072030