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90. Attenuated Reward Prediction Error-modulated connectivity between Ventral Striatum and Crus I/II predicts decreased learning across rounds of a trust game in borderline personality
Borderline personality disorder (BPD) is associated with impulsive, maladaptive social behaviors that result from interpersonal stressors. Here, we extended prior research by testing the effect of reputation on participants’ willingness to invest in a trustee (see Vanyukov et al., 2019 for a review) during a social trust task. 28 BPD participants and 28 Healthy Controls—matched on age and sex—completed a multi-round Trust Game during an fMRI scan. We examined the effect of trustee reputation on PE-modulated connectivity between ventral striatum (VS) — a key region in PE representation — and other brain regions in a generalized Psychophysiological Interaction analysis. We observed group differences in trustee-specific connectivity between VS and bilateral Crus I/II of the cerebellum and in the posterior extent of the IPS. BPD participants exhibited attenuated PE-modulated connectivity with bilateral Crus I/II for the neutral trustee. Furthermore, individual differences in PE-modulated VS connectivity with Crus I/II differentially predicted sharing behavior: heightened connectivity with Crus I/II supported participants learning more quickly in the game and using reputation to guide decisions to a lesser extent. In BPD participants, however, attenuated connectivity for the neutral trustee predicted less adaptation of keep/share decisions over the course of learning. These findings align with prior research on the role of Crus I/II in social cognition (Schmahmann, 2019). Our results suggest PE-modulated connectivity between VS and Crus I/II supports social learning and is weakened in BPD, which may undermine adaptive social decision-making in contexts that require interpersonal trust.