Biomedical Engineering Department, University of Houston, Houston, TX, USA.
Research Service, Minneapolis VA Health Care System, and Departments of Neurology, and of Neuroscience, University of Minnesota, Minnesota, MN, USA.
Clin Neurophysiol. 2023 Jan;145:1-10. doi: 10.1016/j.clinph.2022.10.008. Epub 2022 Oct 31.
To evaluate the functional use of sub-band modulations in somatosensory evoked potentials (SSEPs) to discriminate between the primary somatosensory (S1) and motor (M1) areas and contrast the states of consciousness.
During routine intraoperative cortical mapping, SSEPs were recorded with electrocorticography (ECoG) grids from the sensorimotor cortex of eight patients in the anesthetized and awake states. We conducted a time-frequency analysis on the SSEP trace to extract the spectral modulations in each state and visualize their spatial topography.
We observed late gamma modulation (60-250 Hz) in all subjects approximately 50 ms after stimulation onset, extending up to 250 ms in each state. The late gamma activity enhancement was predominant in S1 in the awake state, where it discriminated S1 from M1 at a higher accuracy (92 %) than in the anesthetized state (accuracy = 70 %).
These results showed that sensorimotor mapping does not need to rely on only SSEP phase reversal. The long latency gamma modulation can serve as a biomarker for primary sensorimotor localization and monitor the level of consciousness in neurosurgical practice.
While the intraoperative assessment of SSEP phase reversal with ECoG is widely employed to delineate the central sulcus, the median nerve stimulation-induced spatio-spectral patterns can distinctly localize it and distinguish between conscious states.
评估体感诱发电位（SSEP）中子带调制的功能，以区分初级体感（S1）和运动（M1）区，并对比意识状态。
在常规术中皮质映射期间，使用麻醉和清醒状态下感觉运动皮层的皮层电图（ECoG）网格记录 SSEP。我们对 SSEP 迹线进行时频分析，以提取每个状态下的光谱调制，并可视化其空间拓扑结构。
我们观察到所有受试者在刺激开始后约 50 毫秒处出现晚期伽马调制（60-250 Hz），在每个状态下可延长至 250 毫秒。在清醒状态下，晚期伽马活动增强主要发生在 S1 区，其对 S1 和 M1 的区分准确率（92%）高于麻醉状态（准确率=70%）。
这些结果表明，感觉运动映射不一定依赖于 SSEP 相位反转。长潜伏期伽马调制可作为初级感觉运动定位的生物标志物，并在神经外科实践中监测意识水平。
虽然术中使用 ECoG 评估 SSEP 相位反转广泛用于描绘中央沟，但正中神经刺激诱导的时空模式可以明显定位它，并区分意识状态。
