基于并行CNN和Transformer的脑电降噪网络
A Parallel CNN and Transformer Network for EEG Denoising
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摘要: 脑电图(electroencephalography, EEG)是一种反映大脑皮层电生理活动的技术,经常用于生物医学领域的各种应用中,但其采集过程容易受到多种噪声的污染,这些噪声会影响EEG信号的准确性和可靠性,因此脑电降噪是EEG分析中必不可少的一步。目前,基于深度学习的方法在多个基准数据集中已展现出优于传统方法的降噪性能,然而现有的基于深度学习的方法仍存在以下问题:现有的网络结构在设计时没有充分考虑信号的时序依赖性。由于不同伪影信号具有不同的形态特征,仅考虑局部或全局的时序依赖性,难以在多种伪影移除任务上获得理想的降噪效果。基于此,本文设计了一种新的脑电降噪网络CTNet。CTNet采用了CNN-Transformer结构,通过结合CNN和Transformer的优点提取潜在的判别性特征,具体来说,CNN单元和Transformer单元分别用于提取局部和全局的时序依赖性特征,通过结合局部和全局的特征更好地抑制伪影信号。为了评估CTNet在EEG降噪方面的性能,本文在四种不同的伪影移除任务上对其进行了评估,实验结果表明,CTNet在各种噪声条件下均具有较强的噪声抑制能力。在公开数据集上的实验结果表明,CTNet在多种伪影上均可获得最低的RRMSE、最高的CC和SNR,如在EMG伪影移除任务中,相比于NovelCNN,CTNet的RRMSE降低了8.67%,CC增加了1.41%,SNR增加了7.06%,上述实验结果证实了该网络在脑电降噪任务上的优越性。Abstract: Electroencephalography (EEG) is a powerful technology used to reflect the electrophysiological activity of the cerebral cortex. It is frequently employed in the field of biomedicine for a variety of applications. However, during the acquisition process, EEG signals are often contaminated with various artifacts, such as muscle activity, eye movements, and heart activity. These artifacts can significantly degrade the quality of the EEG signals, which can adversely affect the subsequent analysis. As a result, artifact removal is an essential step in EEG signal analysis. As of now, deep learning-based methods have demonstrated better denoising performance than traditional methods in several benchmark datasets. However, existing deep learning-based methods still have the following limitation. Specifically, the existing network structures are not fully considered temporal characteristics of the signals. Different artifacts have distinct morphological characteristics, so it is challenging to obtain ideal denoising performance on various artifacts by relying solely on either local or global temporal dependencies. To address the above issue, this paper designed a novel EEG denoising network, named CTNet. CTNet adopted the CNN-Transformer structure, which combined the advantages of convolutional neural networks (CNNs) and Transformers to extract potential discriminative features. The CNN unit and the transformer unit are responsible for extracting local and global temporal features, respectively. The network obtained better artifact suppression ability by combining local and global temporal features. To evaluate the performance of CTNet in EEG denoising tasks, we evaluated the performance of CTNet on four different artifact removal tasks. The experimental results demonstrated that CTNet had strong noise suppression ability under various noise conditions. Furthermore, the proposed network outperformed existing methods and obtained the lowest root mean square error (RRMSE), maximum correlation coefficient (CC), and maximum signal-to-noise ratio (SNR) on various artifacts. For example, in the task of removing electromyography artifacts, CTNet achieved an 8.67% reduction in RRMSE, a 1.41% improvement in CC, and a 7.06% improvement in SNR compared to NovelCNN. In conclusion, the experimental results verified the superiority of CTNet in EEG denoising tasks, making it a promising approach for improving the quality and reliability of EEG analysis.