HKU Engineering Researchers Uncover How the Brain Rapidly Switches Between Internal and External Processing
A team led by Professor Ed X. WU, Chair Professor of Biomedical Engineering & Lam Woo Professorship in Biomedical Engineering, and Dr. Alex T. L. LEONG, Research Assistant Professor from the Department of Electrical and Computer Engineering (ECE) under the Faculty of Engineering at the University of Hong Kong (HKU) has achieved a major breakthrough in understanding how the brain processes information through large-scale network changes. Their findings, published in Nature Communications, reveal that the brain can rewire its networks in just seconds after a brief neural signal—challenging the long-held belief that such changes are slow and gradual, based on imaging techniques like functional MRI (fMRI).
Decoding Fast Brain-Wide Dynamics
The brain is a complex system that constantly adapts to its environment by switching between "internally-oriented" states (such as memory retrieval or daydreaming) and "externally-oriented" states (processing sensory information from the outside world). Traditionally, resting-state fMRI (rsfMRI) has been used to non-invasively map and examine properties of large-scale brain networks in humans and animals when no explicit task is being performed. However, it remained unclear whether these brain networks could change sensitively and quickly enough to support rapid switching between internal and external processes.
The team, together with Drs. Linshan XIE and Xunda WANG Postdoctoral Fellows of the Laboratory of Biomedical Imaging and Signal Processing at HKU, used an innovative optogenetic technique in a rat model to initiate a single neural activity from the excitatory neurons of the thalamus, a key brain region that relays and integrates sensory information to the cortex. They discovered that a single, 10-millisecond pulse could trigger a brain-wide rsfMRI network reconfiguration in as little as two seconds.
Key Findings
This research sheds light on how the brain prioritizes sudden incoming information:
- Rapid Brain Network Reconfiguration: When sensory input from the thalamus is activated, the brain quickly shifts from internally-focused networks to those dedicated to processing external information.
- The Role of Neuromodulatory Hubs: The basal forebrain and hypothalamus act as critical hubs, mediating this switch between internal and external states.
- Neural Synchronization: By performing simultaneous rsfMRI and electrophysiology measurements, the team showed that the rapid network dynamics are directly driven by specific neural activity synchronizations.
This study lays the groundwork for investigating how our brain's architecture supports quick responses to environmental stimuli. Furthermore, given that disruptions in the brain network dynamics are hallmarks of various cognitive and neurological disorders, these results offer a critical framework for future clinical research.
A Proud Achievement
Professor Ed X. Wu, Lam Woo Professor in Biomedical Engineering, said, "This achievement underscores the Faculty of Engineering's and ECE's commitment to interdisciplinary research that pushes the boundaries of biomedical imaging and neuroscience."
The research was supported by the Hong Kong Research Grant Council (C7052-23GF) and the Lam Woo Foundation. The article "Brain-wide resting-state fMRI network dynamics elicited by activation of single thalamic input" published in Nature Communications can be found through this link https://www.nature.com/articles/s41467-025-66104-0
