Abstract
Within the cortico basal ganglia (BG)–thalamic network, the direct and indirect pathways comprise of projections from the cortex to the striatum (STR), whereas the hyperdirect pathway(s) consist of cortical projections toward the subthalamic nucleus (STN). Each pathway possesses a functionally distinct role for action selection. The current study quantified and compared the structural connectivity between 17 distinct cortical areas with the STN and STR using 7 Tesla diffusion weighted magnetic resonance imaging (dMRI) and resting-state functional MRI (rs-fMRI) in healthy young subjects. The selection of these cortical areas was based on a literature search focusing on animal tracer studies. The results indicate that, relative to other cortical areas, both the STN and STR showed markedly weaker structural connections to areas assumed to be essential for action inhibition such as the inferior frontal cortex pars opercularis. Additionally, the cortical connectivity fingerprint of the STN and STR indicated relatively strong connections to areas related to voluntary motor initiation such as the cingulate motor area and supplementary motor area. Overall the results indicated that the cortical–STN connections were sparser compared to the STR. There were two notable exceptions, namely for the orbitofrontal cortex and ventral medial prefrontal cortex, where a higher tract strength was found for the STN. These two areas are thought to be involved in reward processing and action bias.
Highlights
The basal ganglia (BG) collectively refer to a group of interconnected subcortical nuclei
Since a large number of studies used different nomenclature to refer to the same or similar brain regions (e.g., Brodmann, Walkers, Vogts, and “own labeling system”) we summarized these studies into a single cortical area using the anatomical description of the original study
The JZS Bayesian mixed effect model revealed that the model with main effects for subcortical structure and cortical structures, as well as an interaction between these two variables, is preferred over the model without the interaction, by a Bayes factor of >1000
Summary
The basal ganglia (BG) collectively refer to a group of interconnected subcortical nuclei. Together with the cortex and the thalamus, these BG nuclei form an integrative network consisting of a number of loops involved in a wide range of cognitive, limbic, and motor functions (Albin et al, 1989; Alexander and Crutcher, 1990; Alexander et al, 1990; Temel et al, 2005; Haber and Calzavara, 2009). Each circuit is characterized by three functionally distinct pathways: direct, indirect, and hyperdirect. The direct and indirect pathways entail projections from cortex to the STR, while the hyperdirect pathway bypasses the STR and projects from cortex, directly to the STN (Nambu et al, 2002b; Jahanshahi et al, 2015).
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