IEEE Trans Neural Syst Rehabil Eng. 2023;31:2591-2602. doi: 10.1109/TNSRE.2023.3281356. Epub 2023 Jun 13.
Accuracy of electroencephalography (EEG) source localization relies on the volume conduction head model. A previous analysis of young adults has shown that simplified head models have larger source localization errors when compared with head models based on magnetic resonance images (MRIs). As obtaining individual MRIs may not always be feasible, researchers often use generic head models based on template MRIs. It is unclear how much error would be introduced using template MRI head models in older adults that likely have differences in brain structure compared to young adults. The primary goal of this study was to determine the error caused by using simplified head models without individual-specific MRIs in both younger and older adults. We collected high-density EEG during uneven terrain walking and motor imagery for 15 younger (22±3 years) and 21 older adults (74±5 years) and obtained [Formula: see text]-weighted MRI for each individual. We performed equivalent dipole fitting after independent component analysis to obtain brain source locations using four forward modeling pipelines with increasing complexity. These pipelines included: 1) a generic head model with template electrode positions or 2) digitized electrode positions, 3) individual-specific head models with digitized electrode positions using simplified tissue segmentation, or 4) anatomically accurate segmentation. We found that when compared to the anatomically accurate individual-specific head models, performing dipole fitting with generic head models led to similar source localization discrepancies (up to 2 cm) for younger and older adults. Co-registering digitized electrode locations to the generic head models reduced source localization discrepancies by ∼ 6 mm. Additionally, we found that source depths generally increased with skull conductivity for the representative young adult but not as much for the older adult. Our results can help inform a more accurate interpretation of brain areas in EEG studies when individual MRIs are unavailable.
脑电图 (EEG) 源定位的准确性依赖于容积传导头部模型。先前对年轻人的分析表明，与基于磁共振成像 (MRI) 的头部模型相比，简化的头部模型会导致更大的源定位误差。由于并非总是能够获得个体 MRI，研究人员通常使用基于模板 MRI 的通用头部模型。在大脑结构可能与年轻人不同的老年人中使用基于模板 MRI 的头部模型会引入多少误差尚不清楚。本研究的主要目标是确定在没有个体特定 MRI 的情况下使用简化头部模型在年轻和老年人中会产生的误差。我们在不平坦地形行走和运动想象期间收集了 15 名年轻成年人（22±3 岁）和 21 名老年成年人（74±5 岁）的高密度 EEG，并为每个个体获得了 T1 加权 MRI。我们在独立成分分析后进行等效偶极子拟合，使用四个具有不同复杂程度的正向建模管道来获得大脑源位置。这些管道包括：1）具有模板电极位置的通用头部模型或 2）数字化电极位置，3）使用简化组织分割的具有数字化电极位置的个体特定头部模型，或 4）解剖精确分割。我们发现，与解剖精确的个体特定头部模型相比，使用通用头部模型进行偶极子拟合会导致年轻和老年成年人的源定位差异相似（最多 2 厘米）。将数字化电极位置与通用头部模型配准可以将源定位差异减小约 6 毫米。此外，我们发现，对于代表性的年轻成年人，源深度通常随颅骨电导率增加而增加，但对于老年成年人则不然。当无法获得个体 MRI 时，我们的结果可以帮助更准确地解释 EEG 研究中的大脑区域。
