THE PULVINAR ACTIVELY COORDINATES CORTICAL TIMING TO SUPPORT STATE-DEPENDENT VISUAL SYNCHRONIZATION

Effective perceptual processing relies on the synchronization of neuronal activity across distributed cortical networks, a mechanism supporting feature binding and multisensory integration and known to depend on thalamo-cortical interactions. Here, we investigated how transient inhibition of the lateral-medial visual cortical area (LM) affects neuronal synchronization between the primary visual cortex (V1) and the pulvinar nucleus (Pul) of the thalamus in mice. Using extracellular recordings, we quantified intra- and interregional spike synchrony during reversible LM inactivation induced by cryoblockade. LM was inhibited using a cryoloop applied directly to the cortex during two experimental conditions: spontaneous and visually evoked activity (6 mice; n = 787 neurons). Across conditions, intraregional interactions exhibited a characteristic U-shaped synchronization profile, with reduced spike synchrony during LM inactivation followed by a rebound during recovery. In contrast, interregional V1-Pul synchronization was selectively disrupted by LM inhibition during visually evoked activity, while remaining largely preserved during spontaneous activity. In the absence of visual stimulation, V1-Pul interaction delays remained stable during LM inhibition (−210 ms vs. −218 ms). During visual stimulation, intact LM was associated with tight V1-Pul temporal coupling (−46.8 ms), whereas LM inhibition led to a pronounced increase in delay (−324 ms), reverting to a baseline-like timing regime. Ongoing experiments are testing this temporal coordination mechanism using projection-specific silencing of thalamocortical neurons via retrograde Cre delivery from LM combined with a Cre-dependent inhibitory construct in the pulvinar. Together, these findings show that cortico-pulvinar synchronization is dynamically shaped by sensory context and cortical state. Supp : IRSC.