BHI/CAHBIR Virtual Seminar: Kai Hwang

In a series of studies, we examined how the network properties of the human thalamocortical system support behavior and cognition. We first investigated the spatial organization of thalamic task-evoked responses using fMRI data from human subjects who performed a rich battery of tasks encompassing a broad range of cognitive processes. We discovered that multi-task thalamic evoked responses converged onto a low-dimensional architecture. In this setup, an elementary set of basis thalamic activity patterns were evoked across multiple tasks. Specifically, the anterior, medial, and posterior-medial thalamus exhibited a hub-like activity profile, participating broadly in tasks across diverse domains. This is consistent with previous studies that mapped these thalamic regions as network hubs. We then built a network model to test whether thalamocortical functional connectivity could transform thalamic evoked responses into cognitive representations. This model outperformed several comparison models based on other brain structures in predicting cortical task activity, underscoring the pivotal role of thalamocortical interactions in sustaining cognitive representations. The thalamocortical model was subsequently validated through both simulation and empirical observations from human patients with focal thalamic lesions. Finally, we demonstrated that the network properties of the thalamus facilitate cognitive flexibility by updating contextual and task-related information for hierarchical cognitive control. Altogether, this converging evidence suggests that the human thalamus plays a broad role in cognition through its connectivity profile.

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