ABSTRACT
En route from retina to cortex, visual information passes through the dorsolateral geniculate nucleus of the thalamus (dLGN), where extensive corticothalamic (CT) feedback has been suggested to modulate spatial processing. How this modulation arises from direct excitatory and indirect inhibitory CT feedback pathways remains enigmatic. Here we show that in awake mice, retinotopically organized cortical feedback sharpens receptive fields (RFs) and increases surround suppression in the dLGN. Guided by a network model indicating that widespread inhibitory CT feedback is necessary to reproduce these effects, we targeted the visual sector of the thalamic reticular nucleus (visTRN) for recordings. We found that visTRN neurons have large receptive fields, show little surround suppression, and exhibit strong feedback-dependent responses to large stimuli. These features make them an ideal candidate for mediating feedback-enhanced surround suppression in the dLGN. We conclude that cortical feedback sculpts spatial integration in dLGN, likely via recruitment of neurons in visTRN.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Significant changes and additions throughout, including: 1. Anatomical triple-color tracing experiments showing that CT feedback to both dLGN and visTRN is organized in a retinotopic way. 2. Description of the retinotopic organization in mouse visTRN. 3. Separation of CT feedback effects by dLGN and visTRN cell type. 4. Analysis of spatial integration characteristics as a function of cortical depth in area V1. The main results and conclusions of the manuscript remain unchanged.