Differential local synchronization in human nucleus accumbens vs. caudate and putamen

We investigated local synchronization in three nuclei of the human striatum (nucleus accumbens, caudate nucleus, putamen; n = 1,055 participants) by computing, for each nucleus, the zero-lag cross-correlations (CC0) between prewhitened resting-state blood level oxygenation dependent (BOLD) functional magnetic resonance imaging (fMRI) time series recorded from voxels 2-12 mm apart (2-, 4-, 6-, 8-, 10-, 12-mm bins). CC0 was strongest at the shortest distance (2 mm) and decreased with distance in a power (log-log) fit, reaching a plateau at 8 mm. CC0 was highest in accumbens, where it decreased more sharply (by ∼1.4×) with distance than in the caudate and putamen. These results document a distinct difference in synchronization in accumbens as compared with caudate and putamen, where this synchronization was very similar. Given that the cellular layout is fairly comparable in all three nuclei, our findings could be reasonably attributed to a different neuromodulatory environment between accumbens and caudate/putamen, a hypothesis supported by the findings of differential neuromodulatory distributions in humans using positron emission tomography (PET). The role of local synchronization and its different strength among striatal nuclei on their overall function and relations to behavior remains to be elucidated.NEW & NOTEWORTHY We report on a differential local synchronization between nucleus accumbens vs. caudate/putamen. Zero-lag cross-correlations (synchronization) were computed between prewhitened resting-state blood level oxygenation dependent (BOLD)-functional magnetic resonance imaging (fMRI) time-series, recorded in 1,055 participants from 2-mm isotropic voxels 2-12 mm apart. In all nuclei, cross-correlations were strongest at 2 mm, declined with distance as a power-fit, and plateaued at 8 mm. However, they were higher and fell more sharply with distance in accumbens than caudate/putamen, a feature whose significance remains to be elucidated.