Research

We are currently recruiting talented post-docs, graduate students, and research assistants. Please email Kai (kai-hwang@uiowa.edu) if you are interested!

Network mechanisms of cognitive control: We study how brain networks interact to transmit, select, or inhibit information for flexible human behaviors.

Network mechanisms of neurocognitive development: We investigate the contribution of brain network development to cognitive control, and pinpoint specific neural processes that contribute to behavioral change from childhood to adolescence.

Methods: Our research utilizes a variety of methods, including fMRI, TMS, MEG, EEG, task-free (resting-state) and task-based connectivity analyses, graph analyses, classical cognitive and oculomotor paradigms, and studies of patients with focal cortical or subcortical lesions.


Network topographic properties of thalamocortical connectivity

Thalamocortical

The mammalian brain can be conceptualized as a thalamocortical system, yet the thalamus is often ignored in studies of brain network organization. By combining graph analyses on thalamocortical functional connectivity, meta-analysis on task-based functional neuroimaging experiments, and studies of patients with focal thalamic lesions, We are investigating the thalamus's functional contribution to human brain's functional network organization.

  • Hwang, K., Bertolero M., Liu, W., D’Esposito, M. (2017). The human thalamus is an integrative hub for functional brain Networks. Journal of Neurosciene. 37(23), 5594-5607
  • Hwang, K., D’Esposito M. (2015). Cortical connectomal diaschisis in patients with subcortical thalamic or striatal lesions. Organization for Human Brain Mapping. Honolulu, HI.
  • Thalamus medating interactions bewteen large-scale cortical functional networks for cognitive control

    Thalamocortical

    The cerebral cortex is composed of several large-scale functional networks, and the interaction between these networks (inter-network connectivity) is known to fluctuate across time and modulated by cognitive demands. We investigate if and how the thalamus modulates or mediates inter-network connectivity, and how it might contribute to cognitive control.

    Specific projects include: (1) Testing the possibility of inducing downstream physiological change in the thalamus through cortical TMS stimulation. (2) Examining task-related thalamocortical connectivity during effortful, cognitively demanding behavioral paradigms that are known to induce changes in global brain connectivity patterns.

  • Hwang, K., Bertolero, M., Teng, A., D’Esposito, M. (2017). The thalamus mediates interactions between large-scale cortical functional networks. Organization for Human Brain Mapping. Vancouver, Canada.
  • Discovering neural substrates for modulating task-related functional connectivity

    MTD

    Could functional connectivity be modulated by "top-down biasing signals"? In collaboration with Dr. Mac Shine at Stanford University, we are studying how cognitive control influences information exchange between task-related brain regions, and to identify brain regions interacting with dynamic functional connectivity patterns. We use TMS to causally map regions that provide "biasing signals" to enhance or inhibit functional connectivity for cognitive control.

  • Hwang, K., Shine, J.M., Cellier, D., D’Esposito, M. (In Press). The human intraparietal sulcus modulates task-evoked functional connectivity. Cerebral Cortex.
  • Hwang, K., Shine, J.M., D’Esposito, M. (2019). Frontoparietal Activity Interacts With Task-Evoked Changes in Functional Connectivity. Cerebral Cortex. Link to paper.
  • Oscillatory neural dynamics, cognitive control, and development

    MTD

    How do brain networks flexibly process and communicate information? Possibly through oscillatory neural activities. Different brain rhythms are thought to reflect distinct biophysical and circuit-level processes, thus could be indices of distinct neurocognitive mechanisms. Very little is known about how oscillatory neural dynamics develops; We study how oscillatory neural dynamics support cognitive control in adults and during adolescent development.

  • Riddle, J., Hwang, K., Cellier, D., Dhanani, S., D’Esposito, M. (2019). Causal evidence for the role of neuronal oscillations in top-down and bottom-up attention. Journal of Cognitive Neuroscience.
  • Hwang, K., Ghuman A.S., Manoach, D.S., Jones, S.R., Luna, B. (2016). Frontal preparatory neural oscillations associated with cognitive control: A developmental study comparing young adults and adolescents. NeuroImage, 136:139-48.
  • Hwang, K., Ghuman A.S., Manoach, D.S., Jones, S.R., Luna, B. (2014). Cortical Neurodynamics of Inhibitory control. Journal of Neuroscience, 34(29):9551:9561.
  • The development of functional brain network architecture and thalamocortical connectivity

    hub

    Historically, cognitive control and its neurodevelopment have been studied using univariate approaches to probe relevant brain regions in isolation. However, several brain maturational processes (e.g., myelination) affect the brain as a network from childhood through adolescence. Hence, how functional brain networks are organized across development has important implication to its information processing capacity. We apply graph theoretic approaches to analyze brain network properties throughout development. Right now we are focusing the thalamocortical system; despite it critical importance, not enough is known about its developmental trajectory.

  • Marek, S.A., Hwang, K., Foran, W.W., Luna, B. (2015). The role of network organization and integration in the development of cognitive control. PLOS Biology, 13(12): e1002328. doi:10.1371/journal.pbio.1002328.
  • Hwang, K., Hallquist, M.N., Luna, B. (2013). The development of hub architecture in the human functional brain network. Cerebral Cortex, 23(10):2380-2393.
  • Hwang, K., Luna, B. (2012). The development of brain connectivity supporting prefrontal cortical functions. D.T. Stuss & R.T. Knight (Eds.) Principle of frontal lobe functions, 2nd Ed. New York: Oxford University Press.