Role of Thalamus in Human Conscious Perception Revealed by Low-Intensity Focused Ultrasound Neuromodulation.

The neural basis of consciousness remains incompletely understood. While cortical mechanisms of conscious perception have been extensively investigated in humans, the role of subcortical structures, including the thalamus, remains less explored. Here, we elucidate the causal contributions of different thalamic regions to conscious perception using transcranial low-intensity focused ultrasound (LIFU) neuromodulation. We hypothesize that modulating distinct thalamic regions alters perceptual outcomes derived from Signal Detection Theory. We apply LIFU to healthy human anterior (transmodal-dominant) and posterior (unimodal-dominant) thalamic regions, further subdivided into ventral and dorsal regions, during a near-threshold visual perception task. We show that high duty cycle modulation of the ventral anterior (VA) part of thalamus enhances object recognition sensitivity. Sensitivity enhancement magnitude correlates with the core-matrix cell compositions of the stimulated thalamic region. Connectivity analysis of a large-scale functional magnetic resonance imaging dataset confirms strong transmodal connectivity of VA thalamus with frontoparietal and default-mode networks. We also demonstrate target-invariant effects of high duty cycle LIFU disrupting object categorization accuracy. These findings provide causal insight into the cytoarchitectural and functional organization of the thalamus that shapes human visual experience, especially the role of matrix cell-rich, transmodal-dominant VA thalamus.