Researchers at the University of California, Los Angeles and their colleagues at Emory University and other research centers have combined data modeling and experimental observations to bridge the gap between the two main properties of the large-scale organization of the human brain – stationary and running waves of activity.
“Functional magnetic resonance imaging shows that the brain has a globally coherent spatial structure, but there is still no consensus among scientists about the correct way to catalog this structure. We show that a small number of spatio-temporal patterns can do the job,” said Lucina Udin. , professor of psychiatry and biobehavioral sciences and director of the Brain Connectivity and Cognition Lab at the UCLA Semel Institute for Neuroscience and Human Behavior.
Taylor Bolt, a statistician at the lab and first author of the study, said: “We have shown that a wide range of previously observed empirical phenomena are manifestations of three basic spatiotemporal patterns.”
The research focuses on spontaneous low-frequency fluctuations dependent on blood oxygen saturation level (BOLD), a phenomenon discovered in the 1990s. Spontaneous oscillations have been subjected to increasingly sophisticated analytical methods, leading to a vast landscape of competing descriptions of the large-scale functional organization of the brain. Some researchers emphasize the simultaneous synchrony of brain regions in the cortex – what the authors call a “standing” or “stationary” wave structure. Other researchers have identified time-delayed synchrony in cortical areas — what the authors call a “propagation” or “current” wave structure. There have been “few attempts to synthesize results from different approaches,” the researchers said.
Uddin compared the lack of consensus to the Indian parable of the blind men and the elephant, where each person encounters one part of the animal and comes up with a description that differs from all the others. “The parable teaches us the dangers of missing the ‘big picture’ because of our own limited observations,” she said.
Hypothesizing that standing-wave and traveling-wave representations of “the brain’s intrinsic functional organization encompass different aspects of a small number of spatiotemporal patterns,” the authors found that a number of previous observations could be combined within modeling of both standing-wave and traveling-wave structure . The researchers said their findings provide “a description of the global functional organization of the brain that may inspire new hypotheses about the mechanisms underlying the coordination of activities in the brain.”
Uddin and Jason Nomi, assistant research scientist at the UCLA Semel Institute for Neuroscience and Human Behavior, collaborated on the study with an international team, including senior author Sheila Keilholtz of Emory University in the US; Dr. Danilo Bzdok from McGill University in Canada; Jorge Salas and Cathy Chung from Vanderbilt University in the US; and Thomas Yeo of the National University of Singapore. The study was published in the July 28, 2022, issue Neuroscience of nature.
Funding: This work was supported by grants from the Canadian Institute for Prospective Research, R01MH107549 from the National Institute of Mental Health (NIMH) to Uddin, and an NIMH award (R03MH121668) and a NARSAD Young Investigator Award to Nomi. Keilholz is funded by R01MH111416, R01NS078095, and R01EB029857.
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