Shared Fine-Scale Functional Organization in the Human Subcortex Revealed by Connectivity Hyperalignment

Subcortical structures play a crucial role in cognition, emotion, and social processing, yet their fine-scale functional organization has been difficult to study via group-level fMRI analysis. This is because nuclei are small and have low signal-to-noise ratios, and their functional topographies differ significantly across individuals despite anatomical alignment attempts.

The variability in functional connectivity has real implications, as deep brain stimulation targets with greater functional connectivity variability show less consistent clinical outcomes. However, researchers have now discovered that the seemingly idiosyncratic subcortical organization actually reflects a shared, fine-grained structure that can be uncovered by modeling each individual's connectivity in a common functional space, rather than relying on anatomical correspondence.

By applying this approach to fMRI data collected during naturalistic movie viewing, the study found that aligning subcortical voxels based on their cortical connectivity, rather than their anatomical location, significantly improved cross-subject correspondence in both stimulus-evoked responses and connectivity profiles. Importantly, this alignment enhanced rather than diminished the local structure, making neighboring voxels more functionally distinct from one another, and cortical connectivity targets substantially more decodable across subjects.

This finding suggests that human subcortical nuclei share a common fine-scale functional architecture that is obscured by anatomical variability but can be revealed at the individual level. This breakthrough changes the way researchers approach subcortical neuroimaging, as it shows that group-level analyses can achieve voxel-level precision by aligning function rather than anatomy, paving the way for a more detailed exploration of cortical-subcortical circuit organization.