OPTOGENETIC STIMULATION OF THE LATERAL GENICULATE NUCLEUS AND ITS IMPACT ON CORTICAL ACTIVITY AND VISUAL BEHAVIOR

The lateral geniculate nucleus (LGN) is a thalamic relay that conveys retinal input to the primary visual cortex (V1) and shapes early visual processing (Briggs&Usrey, 2007). Electrical LGN stimulation can evoke visual percepts, showing its potential for visual prosthetics (Pezaris&Reid, 2007). Optogenetic stimulation offers a cell-type specific and temporally precise alternative, allowing selective activation of excitatory LGN relay neurons (Gauvain et al., 2021). However, how LGN optogenetic stimulation influences cortical activity in V1 and visual behavior remain poorly understood.

To address this question, we first compared different viral constructs varying capsids and promoters targeting LGN neurons to express an opsin efficiently. Expression patterns were assessed histologically to verify specificity and spatial restriction within the LGN, and the most reliable constructs were selected for functional experiments. Optogenetic stimulation of infected LGN neurons was then combined with electrophysiological recordings using an optrode to measure thalamic responses, while epicortical (ECoG) recordings in V1 monitored cortical activity.

Using the optimal viral construct, a microLED is implanted in the LGN to deliver focal optogenetic stimulation. Stimulation parameters and locations were systematically varied while recording V1 responses. To assess perceptual relevance, mice are trained in a visual detection task in which LGN stimulation is paired with reward, and behavioral responses are quantified. This approach will establish a causal link between optogenetic LGN stimulation, thalamocortical activity, and visual behavior. By defining stimulation parameters that preserve physiological dynamics, this work will improve our understanding of thalamocortical processing and inform the development of more precise strategies for visual restoration.