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. Author manuscript; available in PMC: 2022 Jul 1.
Published in final edited form as: Nat Rev Neurosci. 2021 May 6;22(7):389–406. doi: 10.1038/s41583-021-00459-3

Fig. 3 ∣. Patterns and types of circuit connections in cortico-thalamo-cortical loops.

Fig. 3 ∣

a ∣ Simple cortico-thalamo-cortical (CTC) loops involve direct connections between TC and PT or CT neurons. Such loops are relatively uncommon. b ∣ Complex loops involve IT neurons closing the cortical end of the loop. Complex loops, particularly of the matrix-type, appear to be ubiquitous. The smaller ‘cyclo-plots’ (circular circuit plots with coloured arrows) are included as concise representations of the basic cellular connectivity in each type of loop.