A deep learning pipeline (MAS-PRT) reveals that prenatal CBD, but not THC, uniquely drives weight-dependent hyper-reactivity in maternal pup retrieval

This study investigates the impact of prenatal cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC) exposure on maternal caregiving in C57BL/6J mice, addressing the limitations of manual scoring by introducing the Machine-Automated Scoring of the Pup Retrieval Test (MAS-PRT). This fully automated deep learning pipeline integrates Multi-Animal DeepLabCut for dam and pup tracking with Detectron2 for dynamic nest reconstruction. Validated against 170 manual annotation trials, MAS-PRT achieved high concordance (< 6% deviation), enabling the extraction of granular metrics like path length and encounter distance without experimenter bias. While gestational exposure (GD5–GD18) did not impair general nest-building, pups from both groups exhibited reduced body weight at postnatal day 5. Crucially, the study demonstrates that automated behavioral scoring can detect subtle maternal effects missed by traditional averaging methods. Although standard latency analyses suggested no impairment, Cox proportional hazards modeling revealed a distinct divergence: CBD-exposed dams showed a heightened, weight-dependent probability of retrieving their lightest pups. This paradoxical enhancement in maternal reactivity was absent in THC-exposed dams, indicating that CBD and THC produce distinct maternal behavioral profiles despite similar offspring weight outcomes. Rather than indicating a unilateral deficit, the data suggest that prenatal CBD exposure reshapes the mother-offspring dyad through a convergence of altered offspring distress signaling and modulated maternal sensitivity. Ultimately, MAS-PRT proves to be a robust, scalable tool for behavioral neuroscience. Its ability to uncover nuanced phenotypes obscured by conventional methods provides the precision necessary for defining complex behavioral endophenotypes, establishing a scalable methodology for future neurodevelopmental research on parenting.