A joint research team from Korea and the United States identified a universal pattern in the temporal scale of neural activity, laying the groundwork for understanding the neural circuit structures that enable brain functions.
KAIST announced on the 24th that a collaborative research team consisting of Professor Se-Bum Paik from the Department of Brain and Cognitive Sciences, Professor Min-Hwan Jeong from the Department of Biological Sciences at KAIST, and Professor Daeyeol Lee from Johns Hopkins University confirmed a common temporal scale pattern of region-specific neural activity across various mammalian species' brains, bringing us one step closer to understanding the principles by which the brain represents information.
The cerebral cortex is the most prominent region in the human brain. The cerebral cortex has a sequential hierarchical structure, ranging from areas responsible for sensory information such as the visual cortex to regions responsible for higher cognition such as the prefrontal cortex.
The joint research team observed in their study that the temporal scale of neural activity gradually increases from lower hierarchical areas to higher hierarchical areas, confirming that neural activity in higher brain regions uses relatively longer temporal scales for information processing.
They also revealed that this tendency is commonly present in both primates and rodents, indicating that temporal scale has become an important common variable for processing various tasks in the evolution of mammalian brains.
Conversely, they found that regions such as the thalamus do not exhibit hierarchical changes in temporal scale despite strong connections with the cerebral cortex. The thalamus is an oval-shaped cluster of nuclei deep within the brain that acts as a “relay station” transmitting sensory information to the cerebral cortex. Information transmitted through the thalamus is then delivered to various parts of the cerebral cortex for processes such as perception, judgment, and regulation.
Previous studies showed a correlation in the cerebral cortex regions of humans, monkeys, and rodents where the temporal scale of spontaneous neural activity lengthens with higher anatomical hierarchy. However, the pattern of temporal scale changes during neural activity representing information in the cerebral cortex was previously unknown.
(From left) Dr. Eunju Shin, Department of Biological Sciences, KAIST; Professor Daeyeol Lee, Department of Neuroscience, Johns Hopkins University; Professor Minhwan Jeong, Department of Biological Sciences, KAIST; Professor Sebum Baek, Department of Brain and Cognitive Sciences, KAIST. Provided by KAIST
Accordingly, the joint research team analyzed neural activity measured in the brains of decision-making monkeys, rats, and mice by separating spontaneous components and behavior-related components to determine whether the temporal scales of these two types of activity lengthen as the hierarchical level increases across various cerebral cortex regions.
Furthermore, they expanded the scope of analysis to include the thalamus, a region directly connected to the cerebral cortex, to compare the temporal scales of neural activity.
As a result, the joint research team confirmed that not only the temporal scale of spontaneous neural activity but also that of decision-making behavior-related activity lengthens as it ascends to higher information processing areas in the cerebral cortex (i.e., with higher anatomical hierarchy). In contrast, neural activity temporal scales in the thalamus are generally shorter than those in the cerebral cortex and show no hierarchical variation.
Professor Se-Bum Paik stated, “Through international collaboration, the joint research team succeeded in revealing a universal structural pattern in which the temporal scale of neural activity varies according to anatomical hierarchy. This is expected to enable detailed explanations of the neural network structures necessary to implement various brain functions in the future.”
Meanwhile, this research was conducted with support from the Basic Research Program in Science and Engineering of the National Research Foundation of Korea, the KAIST Singularity Professorship Program, and the Institute for Basic Science. The research results (paper) were also published in the Proceedings of the National Academy of Sciences of the United States of America on the 13th.
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