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FBCNet: A Multi-view Convolutional Neural Network for Brain-Computer Interface (2104.01233v1)

Published 17 Mar 2021 in cs.OH, cs.AI, cs.LG, and eess.SP

Abstract: Lack of adequate training samples and noisy high-dimensional features are key challenges faced by Motor Imagery (MI) decoding algorithms for electroencephalogram (EEG) based Brain-Computer Interface (BCI). To address these challenges, inspired from neuro-physiological signatures of MI, this paper proposes a novel Filter-Bank Convolutional Network (FBCNet) for MI classification. FBCNet employs a multi-view data representation followed by spatial filtering to extract spectro-spatially discriminative features. This multistage approach enables efficient training of the network even when limited training data is available. More significantly, in FBCNet, we propose a novel Variance layer that effectively aggregates the EEG time-domain information. With this design, we compare FBCNet with state-of-the-art (SOTA) BCI algorithm on four MI datasets: The BCI competition IV dataset 2a (BCIC-IV-2a), the OpenBMI dataset, and two large datasets from chronic stroke patients. The results show that, by achieving 76.20% 4-class classification accuracy, FBCNet sets a new SOTA for BCIC-IV-2a dataset. On the other three datasets, FBCNet yields up to 8% higher binary classification accuracies. Additionally, using explainable AI techniques we present one of the first reports about the differences in discriminative EEG features between healthy subjects and stroke patients. Also, the FBCNet source code is available at https://github.com/ravikiran-mane/FBCNet.

Citations (91)

Summary

  • The paper introduces FBCNet, a three-stage multi-view model that enhances motor imagery classification by extracting spectral, spatial, and temporal EEG features.
  • It employs a CNN with depthwise convolutions and a novel variance layer to address challenges of limited training data and noisy high-dimensional signals.
  • FBCNet achieves a new benchmark with 76.20% accuracy on the BCI Competition IV dataset 2a and demonstrates improved performance in chronic stroke patients.

FBCNet: A Multi-view Convolutional Neural Network for Brain-Computer Interface

The paper "FBCNet: A Multi-view Convolutional Neural Network for Brain-Computer Interface" introduces an innovative approach aimed at improving Motor Imagery (MI) classification accuracy, particularly in the context of Brain-Computer Interfaces (BCIs) utilizing electroencephalography (EEG). FBCNet addresses the key challenges of MI decoding these methods face, specifically the lack of adequate training samples and noisy, high-dimensional feature spaces. The proposed method strikes a balance between employing sophisticated deep learning techniques and incorporating neurophysiological knowledge, allowing it to effectively handle the constraints typical of BCI systems, such as limited training data.

The proposed architecture, FBCNet, is characterized by a three-stage process designed to extract spectro-spatially discriminative features efficiently from EEG data. These stages include:

  1. Spectral Localization via Multi-view Data Representation: This step involves filtering EEG data into multiple narrow-band signals, thereby isolating specific frequency ranges relevant to MI tasks.
  2. Spatial Localization by CNN: A Convolutional Neural Network (CNN) extracts spatial patterns from the spectrally localized data. Depthwise Convolutions, specifically, are employed to capture spatial variations associated with different frequency bands.
  3. Temporal Feature Extraction using a Novel Variance Layer: This layer is designed to compute the variance of filtered signals, effectively extracting temporal dynamics critical for distinguishing MI tasks. This novel approach improves the extraction of motor imagery signatures, enhancing classification accuracies.

FBCNet was evaluated using diverse datasets including both healthy individuals and stroke patients. It not only set a new state-of-the-art (SOTA) benchmark with a 76.20% accuracy for the BCI competition IV dataset 2a but also achieved up to 8% higher accuracies for chronic stroke patients compared to existing models. These results indicate that FBCNet's architecture efficiently leverages both machine learning advancements and domain-specific insights, allowing improved performance despite the common data constraints in BCIs.

A critical feature of this paper is its focus on explainability. Utilizing explainable AI techniques, the paper provides insights into the EEG features critical for MI classification. Notably, the paper highlights that FBCNet is capable of identifying EEG patterns typical of stroke patients, significantly differing from those of healthy subjects.

Several implications and potential future directions arise from this paper. Practically, FBCNet's robust performance with limited training data makes it an attractive tool for real-world BCI applications, where collecting extensive datasets can be challenging. Theoretically, FBCNet opens avenues for hybrid approaches that blend deep learning methods with domain-specific knowledge, potentially applicable across various domains where traditional deep learning models struggle with data scarcity or noisy inputs.

In conclusion, FBCNet represents a significant contribution to the BCI domain, offering a pragmatic balance between deep learning capabilities and the incorporation of essential domain knowledge. Its demonstrated potential in both healthy and patient populations suggests broad applicability, encouraging further exploration and refinement in related neural decoding and assistive technology applications.