"The Brain Responds Differently by Layer When Focusing on Touch" [Reading Science]

IBS Elucidates Fine Modulation of Human Sensory Cortex Using 7T fMRI
Published in Nature Communications

When we focus on specific tactile sensations, the brain does not simply amplify signals; instead, it regulates information differently across each layer of the cerebral cortex. This overturns the traditional notion of "uniform amplification" and is significant in that it directly confirms the human brain's precise information processing mechanisms.

The research team led by Sungki Kim, Director of the Center for Neuroscience Imaging at the Institute for Basic Science (IBS) and Professor at the Department of Global Biomedical Engineering at Sungkyunkwan University, reported that in the human sensory cortex, attention does not merely amplify signals but selectively modulates them according to the layer structure of the cortex. The research findings were published online in the international journal Nature Communications on April 13.

Layer-specific changes in cortical sensory activity patterns according to attention. Provided by the research team

Until now, it has been understood that the brain processes information through the interaction of external stimuli (bottom-up) and cognitive regulation such as attention (top-down). However, directly measuring how these signals vary according to the "layer structure" of the human cerebral cortex has remained a technical challenge.

Surface Layers Show "Increase," Deep Layers Show "Decrease"... Precision Modulation by Attention Confirmed

To address this, the research team combined ultra-high field (7 Tesla, 7T) functional magnetic resonance imaging (fMRI) with the spin-echo technique, enabling high-resolution analysis that distinguishes even the fine layer structures of the brain.

By providing tactile stimulation to participants' fingers and simultaneously presenting distracting stimuli to the wrist, the team measured layer-specific responses in the primary somatosensory cortex, comparing cases where participants focused on a particular stimulus with those where they did not.

The results showed that when participants concentrated on the stimulus, signal activity in the surface layers of the sensory cortex increased, while activity in the deep layers actually decreased, demonstrating an opposite pattern. There were no significant changes in the middle layers, and when distracting stimuli were present, signal activity generally decreased across all layers.

This demonstrates that attention does not simply "strengthen" sensory information, but instead, precisely modulates signals in different directions along the layer structure of the brain. Notably, directly identifying this layer-specific cortical response in humans extends existing theories that have mainly been based on animal research.

Sungki Kim, Director of the IBS research group, stated, "By combining ultra-high field fMRI and the spin-echo technique, we were able to precisely measure neural activity across different cortical layers in the human brain. This will serve as a foundation not only for future high-resolution brain imaging studies but also for expanding research into various cognitive and sensory functions."

Dongho Kim, Senior Researcher at IBS, added, "This result confirms how attention selectively regulates information at the layer level. We expect this to have implications not only for research into pain and neurological disorders but also for potential applications in fields such as artificial intelligence."

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