A Closer Look at Corticothalamic "Loops"

• Published in: Frontiers in neural circuits Vol. 15; p. 632668
• Main Author: Rockland, Kathleen S
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Research Foundation 02.02.2021; Frontiers Media S.A
• Subjects: Cerebral Cortex; Cognitive ability; Cortex (somatosensory); cortical cell types; corticogeniculate; Dendrites; Feedback; Gene expression; Geniculate Bodies; heterogeneity; layer 6; Neurons; Neuroscience; reciprocity; Rodents; Thalamus; Topography; Visual cortex; Visual stimuli; Constantinople; cortical cell types; layer 6; corticogeniculate; heterogeneity; reciprocity
• ISSN: 1662-5110; 1662-5110
• DOI: 10.3389/fncir.2021.632668

In this Opinion, I briefly bring together several anatomical features of CT connections, relevant to an emerging view of cognitive-sensory processes; namely, (1) cell type diversity, which may only partly be related to segregated parallel processing; (2) reciprocity, which may not be monosynaptic cell-to-cell and may not be strictly topographic; and (3) the massive convergence of multiple intrinsic cortical and multiple direct and indirect extrinsic connections beyond the primary thalamus. [...]multiple groups of CT neurons have been distinguished on the basis of apical dendritic morphology. [...]in macaque primary visual cortex, six main functional clusters have been reported based on responsiveness to visual stimuli (i.e., achromatic gratings, with varying parameters; Hawken et al., 2020). Other inputs to CT neurons are more numerous than the TC inputs and include a range of intrinsic excitatory, intrinsic inhibitory, and some excitatory cortical feedback inputs (to layer 6 or, in macaque visual cortex, layer 4B for the neurons with longer apical dendrites).