Neuroanatomical and Functional Dimensionality of Reinforcement Sensitivity Theory Systems: An Exploratory Graph Analysis Approach

This study evaluates the neurobiological architecture of Reinforcement Sensitivity Theory (RST) using a network psychometric approach. We shift from region-based inference to system-level organization by studying structural and functional brain dimensionality. Using the Human Connectome Project dataset ( N  = 1113 structural MRI; N  = 176 naturalistic functional MRI), we applied Exploratory Graph Analysis (EGA) to 77 regions of interest from the HCPex atlas contingent to the RST. Bootstrap EGA assessed dimensional stability and item consistency. Structural results identified nine dimensions: the Behavioral Inhibition/Fight-Flight-Freeze (BIS/FFFS) and the Behavioral Approach (BAS) systems, a distinct Constraint Ventral Stream (CVS), and six partially dissociable Constraint Dorsal Stream (CDS) components. In contrast, functional data yielded a more integrated six-dimensional solution. While structural covariance reflects stable anatomical blueprints, functional networks reveal stimulus-driven co-activation, particularly between the BIS/FFFS and BAS. The subdivision of the CDS across both modalities supports a non-unitary control architecture visible only at high parcellation. Our findings demonstrate that RST systems emerge as coordinated, reproducible patterns of brain organization, providing a cumulative framework for linking psychological constructs to biological phenotypes in psychometric neuroscience.