Connections of the dorsolateral prefrontal cortex with the thalamus: a probabilistic tractography study

The dorsolateral prefrontal cortex (DLPFC) is a cortical area involved in higher cognitive functions, and at the center of the pathophysiology of mental disorders such as depression and schizophrenia. Considering these major roles and the development of deep brain stimulation, the object of this study was to assess the patterns of connectivity of the DLPFC with its main subcortical relay, the thalamus, with the help of probabilistic tractography.

We used T1-weighted imaging and diffusion data from 18 subjects from the Human Connectome Project. The DLPFC and the thalamic nuclear groups were defined using the combination of atlases, sulcogyral anatomy and cytoarchitectonic data. Probabilistic tractography was performed from the DLPFC to the thalamus. The patterns of connectivity were assessed using two indexes: (1) a connectivity index (CI) which evaluate the strength of connection (2) an asymmetry index (AI) which explores the inter-hemispheric variability.

The analysis of CI showed significant connections between the DLPFC and the dorsomedial nuclei (p < 0.05), the anterior nuclear groups (p < 0.05) and the right centromedian nucleus (p < 0.05). No link was found between handedness and AI (p > 0.05). Most of subjects (15/18) had a right predominance of the thalamo cortical connections of the DLPFC.

Probabilistic tractography appears as a valuable non-invasive tool for the exploration of the thalamocortical connections between the dorsolateral prefrontal cortex and thalamic nuclei. It allowed to show different inter-hemispheric patterns of connectivity, and highlighted the centromedian nucleus as a key subcortical relay of executive functions.