Individual thalamic inhibitory interneurons are functionally specialized towards distinct visual features

Abstract

Inhibitory interneurons in the dorsolateral geniculate nucleus (dLGN) are situated at the first central synapse of the image-forming visual pathway but little is known about their function. Given their anatomy, they are expected to be multiplexors, integrating many different retinal channels along their dendrites. Here, using targeted single-cell-initiated rabies tracing, we found that mouse dLGN interneurons exhibit a degree of retinal input specialization similar to thalamocortical neurons. Some are anatomically highly specialized, for example, towards direction-selective information. Two-photon calcium imaging performed in vivo revealed that interneurons are also functionally specialized. In mice lacking retinal horizontal direction selectivity, horizontal direction selectivity is reduced in interneurons, suggesting a causal link between input and functional specialization. Functional specialization is not only present at interneuron somata, but also extends into their dendrites. Altogether, each inhibitory interneuron globally encodes one visual feature originating mostly in the retina and is ideally suited to perform feature-selective inhibition.

Retinal input integration in excitatory and inhibitory neurons in the mouse superior colliculusin vivo

“…However, it has to be considered that our in vivo recording technique is limited in capturing the total pool of converging RGC inputs on a neuron (Sibille et al, 2022a). Viral retrograde transsynaptic tracing methods (Muellner and Roska, 2023;Rompani et al, 2017), could be employed to study the full presynaptic RGC pool of single SC neurons. 2) In addition to retinal inputs, the SC receives extensive projections from the visual cortex (V1) that could act as a potential candidate to excite inhibitory neurons.…”

Retinal input integration in excitatory and inhibitory neurons in the mouse superior colliculus in vivo

“…However, it has to be considered that our in vivo recording technique is limited in capturing the total pool of converging RGC inputs on a neuron (Sibille et al, 2022a). Viral retrograde transsynaptic tracing methods (Muellner and Roska, 2023;Rompani et al, 2017), could be employed to study the full presynaptic RGC pool of single SC neurons.…”

Mapping the Retina onto the Brain

“…Like TC neurons, local interneurons (LINs) in dLGN receive input from diverse RGC types (Morgan and Lichtman 2020;Muellner and Roska 2023). RGC convergence appears to be higher for LINs than TC neurons.…”

“…RGC convergence appears to be higher for LINs than TC neurons. Individual LINs select input from nonrandom sets of RGC types to preserve feature-selective responses, similar to TC neurons (Piscopo et al 2013;Muellner and Roska 2023). The mechanisms that regulate RGC connectivity with dLGN LINs remain to be elucidated.…”