The combination of stimulus-driven and modulatory inputs in visual thalamus depend on visual responsiveness and stimulus type

Abstract

In the dorsolateral geniculate nucleus (dLGN) of the thalamus, retinal signals are combined with non-retinal inputs such as corticothalamic (CT) feedback and behavioural state. How these shape dLGN activity remains an open question. We recorded extracellular responses in dLGN of awake mice to a movie stimulus, while photosuppressing CT feedback, tracking locomotion and pupil size. To assess the relative impact of retinal and non-retinal inputs, we fit single neuron responses using generalized linear models. While including CT feedback and behavioural state as predictors significantly improved the model's overall performance, the improvement was especially pronounced for a sub-population of poorly visually responsive neurons. In addition, the impact of CT feedback was faster and more prevalent in the absence of a patterned visual stimulus. Finally, for CT feedback-sensitive dLGN neurons, visual stimuli could be discriminated better when CT feedback was suppressed. Together, these results show that effects of non-retinal inputs in dLGN depend on visual responsiveness and stimulus context.