Research

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 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.
  • Effects of thalamic lesions

    Thalamocortical

    The human thalamus is a difficult region to study because of its small size and deep location. To address this challenge, we are now conducting studies with a novel approach: combining multimodal neuroimaging (fMRI and EEG) and human lesions studies. The goal is to determine how the disruption of thalamocortical interactions after thalamic lesion affects cortical neural activity and behavior. We are now focusing on how the thalamus modulate cortical evoked responses, neural oscillations, and cortico-cortical functional connectivity for cognitive control.

  • Hwang, K., D’Esposito M. (2015). Cortical connectomal diaschisis in patients with subcortical thalamic or striatal lesions. Organization for Human Brain Mapping. Honolulu, HI.
  • Hwang, K., Bruss, J., Tranel, D., & Boes, A. D. (2020). Network localization of executive function deficits in patients with focal thalamic lesions. Journal of Cognitive Neuroscience, 32(12), 2303-2319.
  • Reber, J., Hwang, K., Bowren, M.A., Bruss, J., Tranel, D., Boes, A.D (2021). Cognitive impairment after focal brain damage is associated damages to structural, but not functional network hubs. Proceedings of the National Academy of Sciences 118.19 (2021).
  • Determine the neural and cognitive mechanisms of "inhibition"

    Thalamocortical

    The concept of "inhibition" is central to cognitive control. Examples include rejecting distractor, inhibiting impulses, and resisting unwanted mental intrusions. However, with the exception of the fronto-BG motor "stopping" system, whether or not inhibition is a dissociable neurocognitive mechanism that is distinguishable from other excitation-based phenomenon remains hotly debated. In collaboration with Shaun Vecera. we are developing paradigms to (1) demonstrate the effect of willful inhibition behaviorally, and (2) identify its corresponding neural signature and its underlying neural substrate using both EEG and fMRI. Another related line of research is to examine the interaction between inhibition and working memory. We ask the question, is working memory function is influenced by the need to exert inhibition? If so, how does it work?


    Discovering neural substrates for modulating task-related functional connectivity

    MTD

    Could functional connectivity be modulated by "top-down biasing signals"? In collaboration with Mac Shine at The University of Sydney, 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. (2020). The human intraparietal sulcus modulates task-evoked functional connectivity. Cerebral Cortex. 30(3), 875-887.
  • Hwang, K., Shine, J. M., D’Esposito, M. (2019). Fronto-parietal activity interacts with task-evoked changes in functional connectivity. Cerebral Cortex. 29(2):802-813 Link to paper.
  • Cognitive flexibility and hierarchical cognitive control

    Thalamocortical

    The cardinal characteristic of cognitive control is it is flexible and context dependent. We are not governed by the same set of rules in every situation. If so, how do we use circumstantial information to adjust our actions, specifically, adjust mappings between sensory and motor processes? We have developed a paradigm that requires human subjects to switch between action rules depending on a superordinate, circumstantial context. Parallel EEG and fMRI studies are now in progress.


  • Hwang, K., Cellier, D., Pipoly, M., (2019). Contextually-driven set-switching modulates theta-band oscillatory power. Society for Neuroscience Annual Meeting, Chicago, IL.
  • Riddle, J., Vogelsang, D. A., Hwang, K., Cellier, D., & D'Esposito, M. (2020). Distinct oscillatory dynamics underlie different components of hierarchical cognitive control. Journal of Neuroscience, 40(25), 4945-4953.

  • 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.

  • Cellier, D., Riddle, J., Petersen, I., & Hwang, K. (2021). The development of theta and alpha neural oscillations from ages 3 to 24 years. Developmental Cognitive Neuroscience, 100969.
  • 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

    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.