Topographic organization of connections between prefrontal cortex and mediodorsal thalamus: Evidence for a general principle of indirect thalamic pathways between directly connected cortical areas

Abstract

Our ability to act flexibly, according to goals and context, is known as cognitive control. Hierarchical levels of control, reflecting different levels of abstraction, are represented across prefrontal cortex (PFC). Although the mediodorsal thalamic nucleus (MD) is extensively interconnected with PFC, the role of MD in cognitive control is unclear. Tract tracer studies in macaques, involving subsets of PFC areas, have converged on coarse MD-PFC connectivity principles; but proposed finer-grained topographic schemes, which constrain interactions between MD and PFC, disagree in many respects. To investigate a unifying topographic scheme, we performed probabilistic tractography on diffusion MRI data from eight macaque monkeys, and estimated the probable paths connecting MD with each of all 19 architectonic areas of PFC. We found a connectional topography where the orderly progression from ventromedial to anterior to posterolateral PFC was represented from anteromedial to posterolateral MD. The projection zones of posterolateral PFC areas in MD showed substantial overlap, and those of ventral and anteromedial PFC areas in MD overlapped. The exception was cingulate area 24: its projection zone overlapped with projections zones of all other PFC areas. Overall, our data suggest that nearby, functionally related, directly connected PFC areas have partially overlapping projection zones in MD, consistent with a role for MD in coordinating communication across PFC. Indeed, the organizing principle for PFC projection zones in MD appears to reflect the flow of information across the hierarchical, multi-level PFC architecture. In addition, cingulate area 24 may have privileged access to influence thalamocortical interactions involving all other PFC areas.

A thalamo-centric neural signature for restructuring negative self-beliefs

“…MD neurons are uniquely positioned in that they are capable of representing aggregations of cortical signals [41]. Varying levels of input convergence from the PFC, both in terms of magnitude and type, endow MD circuits with a computational role that is capable of simultaneously transforming multiple modalities of information [16, 42].…”

Corticocortical and Thalamocortical Changes in Functional Connectivity and White Matter Structural Integrity after Reward-Guided Learning of Visuospatial Discriminations in Rhesus Monkeys

“…The VP white matter in the mask we used lies inferior and slightly medial to the anterior corona radiata (Zakszewski et al, 2014). The VP connects ventral PFC structures, and contributes fibers to the corona radiata that connects PFC to the dorsal, medial thalamus, in both macaques and humans (Lehman et al, 2011;Jbabdi et al, 2013;Zakszewski et al, 2014;Phillips et al, 2019). The fornix and UF have been strongly associated with learning and memory (see Introduction), and alterations of DTIderived microstructural measures have been reported in the VP of macaques following lesions of the hippocampus (Shamy et al, 2010;Meng et al, 2014).…”

Concurrent brain parcellation and connectivity estimation via co‐clustering of resting state fMRI data: A novel approach

“…Connectional topography plays important role in brain functions and behaviors, and can provide insight into neurodevelopment, too (Phillips, Fish, Kambi, Redinbaugh, & Saalmann, 2019;Thompson, Mohammadi-Nejad, Robinson, Andersson, & Sotiropoulos, 2020;Wu, Calhoun, Jung, & Caprihan, 2015). Many neuropsychiatric disorders, such as schizophrenia, have been manifested by disrupted communications for connections between distributed brain networks (Gong et al, 2019;Jiang et al, 2019;Kim et al, 2020;Rolls et al, 2020;Sheffield, Rogers, Blackford, Heckers, & Woodward, 2020).…”