Verbal recall captures neural encoding of a drug-themed movie in heroin use disorder

Language transforms subjective internal states into observable behavior, enabling investigation of the neurocognitive dynamics central to psychiatric conditions. Intense emotional and physiological responses to evocative drug-related contexts precipitate craving and drug seeking in substance use disorders, yet sensitive, accessible behavioral markers of the underlying neural dynamics remain elusive. In this fMRI study, we analyzed individuals unconstrained verbal recall of their subjective experiences after watching a drug-themed movie, including inpatients in treatment for heroin use disorder (HUD) and healthy controls, with speech recorded outside the scanner under minimal instructions. The semantic context of these accounts, assessed using transformer-based embeddings, effectively predicted both HUD diagnosis and treatment progression, with earlier treatment characterized by heightened self-reference and drug focus but less socially oriented recall. Semantic similarities between individuals reflected synchronized activation patterns in dorsal attention and visual networks during movie viewing, linking motivated attentional processing to later recall. With treatment, most HUD-biased semantic features shifted toward control-like patterns, while drug focus persisted; the semantic-neural link was attenuated though partially remained. These results suggest that spontaneous speech, collected offline, can provide a sensitive behavioral readout of both treatment effects and neural encoding of a complex, personally relevant, drug-related context. offering a scalable approach for monitoring neurocognitive dynamics in real-world settings.