Working memory relies on long-range cortical communication via white matter fiber tracts. While the structural role of white matter has been extensively studied, its task-evoked, frequency-specific electrophysiological dynamics during working memory remain unknown. This question matters because oscillatory activity is thought to integrate information across distant brain regions.
A study published in Science Bulletin by teams led by Guoguang Zhao at Xuanwu Hospital Capital Medical University, and Zaixu Cui at the Chinese Institute for Brain Research addressed this question using stereo-electroencephalography (sEEG). The researchers recorded local field potentials from 20 patients with drug-resistant epilepsy during clinical monitoring as they performed a digit N -back working memory task.
The study examined three white matter regions adjacent to working memory-related networks: the frontal blade, the splenium of the corpus callosum/superior parietal blade (SCC/SupParietalB), and the temporal blade. Time-frequency analyses revealed distinct load-related patterns: high-frequency power (30–120 Hz) increased in the frontal blade but decreased in the SCC/SupParietalB with rising load, while the temporal blade showed stable high-frequency responses and a late increase in theta-band (4–8 Hz) power. These region- and frequency-specific patterns show that human white matter exhibits measurable electrophysiological dynamics during working memory.
The researchers also found that within-frequency connectivity between white matter signals remained stable across task conditions, while cross-frequency connectivity changed with load. In particular, the 2-back condition showed stronger theta–high-gamma coupling than the 0-back condition across several tract pairs, suggesting load-related changes in cross-frequency coordination among white matter signals.
Together, these findings show that human white matter exhibits load-dependent, tract- and frequency-specific functional dynamics during working memory. The study supports the physiological relevance of white matter functional signals and their potential link to cognitive impairment in neurological and psychiatric disorders.
Science Bulletin