Among the various functions the brain must perform are those that range from instantaneous processes, such as sensory information processing, to those that require the preservation of content over relatively long periods, such as memory. A joint research team from South Korea and the United States has identified a universal pattern across various temporal scales of brain neural activity, paving the way to understand the circuitry structure of the brain.
A joint research team, including Baek Se-bum, a professor in brain and cognitive sciences at Korea Advanced Institute of Science and Technology (KAIST), Jeong Min-hwan, a professor in life sciences, and Lee Dae-yeol, a professor at Johns Hopkins University in the United States, noted on the 24th that they have made further progress in understanding the principles by which the brain represents information by confirming the patterns of regional neural activity in the brains of various mammalian species that commonly occur. The research findings were published in the Proceedings of the National Academy of Sciences (PNAS) on the 13th.
The cerebral cortex of the human brain is structured hierarchically, from regions responsible for sensory information, like the visual cortex, to regions responsible for higher cognition, such as the prefrontal cortex. The researchers observed that the temporal scale of neural activity gradually increases from lower hierarchical regions to higher ones. In other words, as one moves to the upper regions of the brain, neural activity that uses relatively longer temporal scales for information processing becomes apparent.
The research team also confirmed that this trend exists commonly in primates and rodents. They revealed that the temporal scales for processing various tasks were a significant common variable in the evolution of mammalian brains. On the other hand, they discovered that areas located deep within the brain, such as the thalamus, are strongly connected to the cerebral cortex, yet do not exhibit hierarchical changes in temporal scale.
The researchers divided the measured neural activities in the brains of monkeys, rats, and mice performing decision-making behaviors into spontaneous factors and behavior-related factors. They analyzed whether the changes in the two types of temporal scales exhibit a pattern of increasing length as the hierarchy of various cerebral cortex regions rises. Additionally, they expanded their analysis to include regions that have direct connections to the cerebral cortex, such as the thalamus, to compare the temporal scales of neural activity.
As a result, the temporal scales of activity related to decision-making also increased as the regions of higher information processing in three types of cerebral cortex were reached, specifically as the anatomical hierarchy rose. In contrast, the temporal scales of neural activity in the thalamus, another area of the brain, were generally shorter than those in the cerebral cortex, and there was no pattern of hierarchical change.
Professor Baek Se-bum stated, "The temporal scale of neural activity, which is a crucial clue to understanding the principles by which mammalian brains process information, has revealed a universal structural pattern that varies according to anatomical hierarchy. I expect it will become possible to provide concrete explanations about the neural network structures necessary to implement the brain's various functions. This achievement is particularly meaningful as it results from the close international collaboration of the researchers."
Reference materials
PNAS (2024), DOI: https://doi.org/10.1073/pnas.2415695121