In a pioneering study published in Science Advances, a team led by Purdue University's Weldon School of Biomedical Engineering, scientists have made significant strides in unraveling the complex neural processes underlying touch perception. Their research, which combines cutting-edge imaging techniques with advanced electrophysiology, provides unprecedented insights into how the brain processes sensory information. Specifically, processing touch events happens very quickly in the brain, but how does this work? This team has put together a new combination of neural recording techniques (patent pending) that provides new insight into the mechanisms underlying touch processing and highlights the crucial role of brain waves.

The study, led by Krishna Jayant, the Leslie A. Geddes Assistant Professor of Biomedical Engineering, utilized custom-fabricated semi-transparent NeuroGrids to simultaneously perform electrophysiology and two-photon calcium imaging across the somatosensory cortex. This innovative approach allowed the researchers to map touch-evoked traveling waves and their corresponding microcircuit dynamics with remarkable precision.

The Study

The team showed that passive and active whisker touch triggered traveling waves within and across barrel cortex regions. These waves consisted of a rapid early component followed by a slow late wave lasting hundreds of milliseconds—a type of “echo” that appeared to reverberate through the brain following sensory stimulation. The study further uncovered that late waves were influenced by motor cortex feedback, shaped by the perceived value of the sensory input, and could predict behavioral choices in a two-whisker discrimination task. From a circuit perspective, the slow wave engaged a sparse ensemble pattern across layer 2/3 of the cortex.

“The study highlights certain key elements involved in orchestrating sensory dynamics. Namely, the nature of sparse activation as a function of feedforward and feedback circuitry and also highlights the critical nature of the concept of traveling waves in enabling optimal integration and translaminar coupling,” said Jayant.

“Mapping the circuit mechanisms underlying traveling waves is significant for understanding brain function and information processing. Traveling waves are spatially extended patterns of neural activity that move across the cortical surface. By studying these mechanisms, we believe we can gain insights into how the brain encodes and decodes information, particularly in processes like working memory and sensory perception,” stated Daniel Gonzales, the first author of the study and former Howard Hughes Hanna Gray Postdoctoral Fellow and Purdue University Lillian Gilbreth Fellow and now Assistant Professor in the Biomedical Engineering Department at Vanderbilt University.

Lyle Muller, a professor of mathematics at Western University, Ontario, and a senior author on the study employed a balanced-state network model to explain the sparse ensemble pattern, attributing it to feedback-induced circuit re-organization. “This finding provides interesting experimental evidence for sparse waves, which we hypothesized to exist based on several theoretical studies of circuit models for cortex” stated Muller.

The team also investigated the role of translaminar cortical circuits and their relationship to traveling waves. Such mechanisms could establish the circuits through which brain waves are coordinated. The team showed how precise activity patterns across cortical layers support specific signatures of traveling waves. “The study's results reveal that translaminar spacetime patterns, organized by cortical feedback, support sparse touch-evoked traveling waves. This discovery marks a significant advancement in our understanding of sensory perception, particularly in touch processing,” said Scott Pluta, Assistant Professor of Biology and a senior author of the study.

What does this mean for the Brain?

The implications of this research are groundbreaking and can potentially revolutionize our understanding of neuroscience and its applications. Understanding traveling waves is essential for uncovering how neural circuits operate and transmit information over long distances. This knowledge will clarify the variability in synchronization and organization across different brain regions, revealing important insights into neural communication and pattern formation.  

“This work will not only enhance our comprehension of sensory processing disorders but also pave the way for developing advanced neural interfaces. As we deepen our understanding of these intricate neural mechanisms, we are on the verge of discovering innovative treatments for sensory-related conditions and making significant advancements in human-machine interactions and neuro-inspired artificial intelligence. Ultimately, however, this research will refine our understanding of computation in awake brains, significantly advancing our knowledge of cognitive processes and brain disorders,” emphasized Jayant.

The Air Force Office of Scientific Research generously supported this high-risk, high-impact study through the Cognitive and Computational Neuroscience program. This research was also supported in part by the National Institutes of Health Director’s New Innovator Award and the Human Frontiers Science Program to Jayant.

About Purdue Innovates Office of Technology Commercialization

The Purdue Innovates Office of Technology Commercialization operates one of the most comprehensive technology transfer programs among leading research universities in the U.S. Services provided by this office support the economic development initiatives of Purdue University and benefit the university’s academic activities through commercializing, licensing and protecting Purdue intellectual property. In fiscal year 2024, the office reported 145 deals finalized with 224 technologies signed, 466 invention disclosures received and 290 U.S. and international patents received. The office is managed by the Purdue Research Foundation, which received the 2019 Innovation and Economic Prosperity Universities Award for Place from the Association of Public and Land-grant Universities. In 2020, IPWatchdog Institute ranked Purdue third nationally in startup creation and in the top 20 for patents. The Purdue Research Foundation is a private, nonprofit foundation created to advance the mission of Purdue University. Contact otcip@prf.org for more information.

About AFOSR: The Air Force Office of Scientific Research (AFOSR), expands the horizon of scientific knowledge through its leadership and management of the Department of the Air Force's basic research program. As a vital component of the Air Force Research Laboratory (AFRL), AFOSR's mission is to discover, shape, champion, and transition high-risk basic research to profoundly impact the future Air and Space Force

Jayant disclosed his innovation to the Purdue Innovates Office of Technology Commercialization, which has applied for a patent (patent pending) from the U.S. Patent and Trademark Office to protect the intellectual property. Industry partners interested in developing or commercializing the innovation should contact otcip@prf.org and refer to track code.