Neural correlates of licking behavior modulated by target position in the striatal matrix compartment.

The striatum is a major cortical input site of the basal ganglia and plays a critical role in the control of orofacial movements such as licking. However, how striatal activity relates to the spatial features of licking behavior remains unclear. In this study, we examined whether neural activity in the striatal matrix and striosomal compartments is associated with the spatial position of a licking target during an operant task. Head-fixed male mice performed a licking task in which the target positions were varied across three spatial dimensions. Using fiber photometry in Calb1-IRES-Cre (n = 7) and Pdyn-IRES-Cre (n = 6) mice, we recorded calcium signals from matrix and striosomal neurons. Associations between neural activity, target position, and behavioral variables were quantified using linear mixed-effects modeling with cross-validation. Matrix activity prior to the first detected lick was associated with reaction time and the dorsal-ventral target position. During licking, matrix activity was associated with the anterior-posterior and medial-lateral positions, independent of reaction time and lick count, whereas striosomal activity was associated with the dorsal-ventral position. These associations were correlational and differed in strength. The association between matrix activity and the anterior-posterior and medial-lateral positions was the most robust. The present findings are limited to male mice and to the hemisphere ipsilateral to the spout.