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Abstract
Recent neuroimaging experiments have defined low-dimensional gradients of functional
connectivity in the cerebral cortex that subserve a spectrum of capacities that span
from sensation to cognition. Despite well-known anatomical connections to the cortex,
the subcortical areas that support cortical functional organization have been relatively
overlooked. One such structure is the thalamus, which maintains extensive anatomical
and functional connections with the cerebral cortex across the cortical mantle. The
thalamus has a heterogeneous cytoarchitecture, with at least two distinct cell classes
that send differential projections to the cortex: granular-projecting 'Core' cells
and supragranular-projecting 'Matrix' cells. Here we use high-resolution 7T resting-state
fMRI data and the relative amount of two calcium-binding proteins, parvalbumin and
calbindin, to infer the relative distribution of these two cell-types (Core and Matrix,
respectively) in the thalamus. First, we demonstrate that thalamocortical connectivity
recapitulates large-scale, low-dimensional connectivity gradients within the cerebral
cortex. Next, we show that diffusely-projecting Matrix regions preferentially correlate
with cortical regions with longer intrinsic fMRI timescales. We then show that the
Core-Matrix architecture of the thalamus is important for understanding network topology
in a manner that supports dynamic integration of signals distributed across the brain.
Finally, we replicate our main results in a distinct 3T resting-state fMRI dataset.
Linking molecular and functional neuroimaging data, our findings highlight the importance
of the thalamic organization for understanding low-dimensional gradients of cortical
connectivity.