Thalamus plays a central role in ongoing cortical functioning


Several challenges to current views of thalamocortical processing are offered here. Glutamatergic pathways in thalamus and cortex are divided into two distinct classes: driver and modulator. We suggest that driver inputs are the main conduits of information and that modulator inputs modify how driver inputs are processed. Different driver sources reveal two types of thalamic relays: first order relays receive subcortical driver input (for example, retinal input to the lateral geniculate nucleus), whereas higher order relays (for example, pulvinar) receive driver input from layer 5 of cortex and participate in cortico-thalamo-cortical (or transthalamic) circuits. These transthalamic circuits represent an unappreciated aspect of cortical functioning, which I discuss here. Direct corticocortical connections are often paralleled by transthalamic ones. Furthermore, driver inputs to thalamus, both first and higher order, typically arrive via branching axons, and the transthalamic branch often innervates subcortical motor centers, leading to the suggestion that these inputs to thalamus serve as efference copies.

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Figure 1: Glutamatergic drivers and modulators in the lateral geniculate nucleus (LGN) showing inputs to geniculate relay cells.
Figure 2: Population data showing distributions of various parameters for driver and modulator inputs to thalamic and cortical cells.
Figure 3: Different circuits for layer 6 corticothalamic inputs involving the layer 6 cells, thalamic relay cells and local GABAergic neurons, which include both cells of the thalamic reticular nucleus (TRN) as well as interneurons.
Figure 4: Examples of branching axons of driver inputs to thalamus.
Figure 5: Two views of thalamocortical processing.


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This work was supported by grants DC008794 and EY022338 from the US National Institutes of Health. I thank J. DeFelipe for providing the images used in Figure 4b,d and H. Kita for the image used in Figure 4c. I also thank R.A. Eatock, D. Freedman and P. Mason for comments on earlier drafts and R.W. Guillery for ongoing conversations with the author and contributions regarding all of the issues raised herein.

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Correspondence to S Murray Sherman.

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Sherman, S. Thalamus plays a central role in ongoing cortical functioning. Nat Neurosci 19, 533–541 (2016) doi:10.1038/nn.4269

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