UCLA researchers and colleagues at Emory University and other research centers have combined data simulation and experimental observation to bridge the gap between two major properties of the large-scale organization of the human brain : stationary and itinerant activity waves.
“Functional magnetic resonance imaging suggests that the brain has a globally consistent spatial structure, but there is not yet consensus among scientists on the correct way to catalog this structure. We show that a small number of patterns spatio-temporal can do the trick,” said Lucina Uddin. , professor of psychiatry and biobehavioral sciences and director of the Brain Connectivity and Cognition Laboratory at the UCLA Semel Institute for Neuroscience and Human Behavior.
Taylor Bolt, the lab’s statistician and first author of the study, said: “We have shown that a wide range of previously observed empirical phenomena are manifestations of three main spatio-temporal patterns.”
The study focuses on spontaneous low-frequency fluctuations dependent on blood oxygenation level (BOLD), a phenomenon discovered in the 1990s. Spontaneous fluctuations have been subjected to increasingly complex analytical techniques, leading to a vast landscape of competing descriptions of large-scale functional brain organization. Some researchers have highlighted the simultaneous synchrony of brain regions through the cortex – what the authors call a “steady” or “stationary” wave structure. Other researchers have highlighted the temporal synchronization of brain regions through the cortex – what the authors call a “propagating” or “travelling” 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 man encounters a part of the animal and comes up with a different description from all the others. “The parable teaches us the dangers of missing the ‘big picture’ due to our own limited observations,” she said.
Assuming that standing and traveling wave representations “of the brain’s intrinsic functional organization capture different aspects of a small number of spatiotemporal patterns”, the authors found that a range of previous observations could be unified. in a framework that models both the standing and traveling wave structure. The researchers said their findings provide a “description of overall functional brain organization that may inspire new hypotheses about the mechanisms underlying the coordination of activity in the brain.”
Uddin and Jason Nomi, an assistant researcher at the UCLA Semel Institute for Neuroscience and Human Behaviour, collaborated on the study with an international team including lead author Shella Keilholz, from Emory University in the US; Dr. Danilo Bzdok, from McGill University in Canada; Jorge Salas and Catie Chang, from Vanderbilt University in the United States; and Thomas Yeo of the National University of Singapore. The study was published in the July 28, 2022 issue of Natural Neuroscience.
Funding: This work was supported by grants from the Canadian Institute for Advanced Research, National Institute of Mental Health (NIMH) R01MH107549 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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