Motor Imagery BCI

Overview

This application is a Brain-Computer Interface (BCI) system designed to classify motor imagery tasks, including left hand, right hand, and neutral state, using EEG data. The system connects to Explore Pro device via the Lab Streaming Layer (LSL) protocol, processes the EEG signals, and classifies the data using machine learning models, including a Transformer-based neural network.

The application supports real-time classification. It includes tools for data collection, preprocessing, model training, and evaluation. The code for the application can be found in our explorepy/examples section on github.

Features

  • Real-Time EEG Data Acquisition: Connects to an EEG device via LSL for real-time data streaming.

  • Motor Imagery Classification: Classifies EEG data into three states: left hand movement, right hand movement, and neutral state.

  • Transformer Model: Implements a Transformer-based neural network for EEG signal classification.

  • Multiple Classifiers: Supports Linear Discriminant Analysis (LDA), Support Vector Machines (SVM), Random Forest (RF), and the custom Transformer model.

  • Data Preprocessing: Includes bandpass filtering for mu and beta bands and feature extraction using band power.

  • Model Training and Evaluation: Allows training and evaluation of multiple classifiers with visualization of results.

  • Real-Time BCI Operation: Runs in continuous mode for real-time classification and control.

Requirements

Hardware

  • An Explore Pro device.

  • A computer with sufficient processing power.

    A GPU is recommended for Transformer model training.

Software

  • Python 3.10 or higher.

  • Required Python packages.

    Install them via pip:

pip install pylsl numpy scipy scikit-learn torch matplotlib seaborn pandas

Ensure your EEG device is set up and streaming data via LSL.

Usage

Collect Calibration Data

To train the classifiers, you need to collect calibration data. Run the following command and follow the on-screen instructions:

python main.py

Choose option 1 to train and compare all classifiers.

The system will prompt you to perform left hand, right hand, and neutral state tasks.

Train Classifiers

The application will automatically preprocess the data, extract features, and train multiple classifiers, including LDA, SVM, Random Forest, and Transformer.

Training progress and results will be displayed in the console.

Run Real-Time BCI

After training, you can run the BCI in real-time mode:

python main.py

Choose option 2 to run the BCI with the best-performing classifier or option 3 to select a specific classifier.

File Structure

motor-imagery-bci/
├── models/                  # Saved classifier models
├── dataset/                 # Saved calibration datasets
├── main.py                  # Main application script
├── README.md                # This file

Classifiers

The application supports the following classifiers:

  • Linear Discriminant Analysis (LDA)

  • Support Vector Machine (SVM)

  • Random Forest (RF)

  • Transformer Model

Customizing the Transformer Model

The Transformer model is defined in the EEGTransformer class. You can customize the following parameters:

  • input_dim: Input feature dimension.

  • num_classes: Number of output classes.

    Default: 3

  • d_model: Dimension of the model.

    Default: 64

  • nhead: Number of attention heads.

    Default: 8

  • num_layers: Number of Transformer encoder layers.

    Default: 4

  • dropout: Dropout rate.

    Default: 0.2

Example:

model = EEGTransformer(input_dim=64, num_classes=3, d_model=128, nhead=8, num_layers=6, dropout=0.3)

Data Preprocessing

The EEG data is preprocessed as follows:

  • Bandpass Filtering: Applied to extract mu (8-12 Hz) and beta (16-24 Hz) bands.

  • Feature Extraction: Band power is calculated for each frequency band.

  • Dataset Preparation: Features and labels are saved in a CSV file for training.

Real-Time Operation

In real-time mode, the application:

  1. Continuously collects EEG data from the LSL stream.

  2. Applies preprocessing and feature extraction.

  3. Classifies the data using the selected model.

  4. Displays the detected state, either left hand, right hand, or neutral, and the certainty level.

Troubleshooting

LSL Stream Not Found

  • Ensure your device is properly connected and streaming data.

  • Verify the stream name in the MotorImageryBCI class initialization.

Poor Classification Accuracy

  • Collect more calibration data.

  • Adjust the frequency bands, mu_band and beta_band, in the MotorImageryBCI class.

  • Fine-tune the Transformer model parameters.

Performance Issues

  • Use a GPU for training the Transformer model.

  • Reduce the window size or overlap in the MotorImageryBCI class.

Future Improvements

While the current system is functional, several enhancements can improve its accuracy, real-time performance, and adaptability.

Advanced Deep Learning Models

  • Replace traditional classifiers, including LDA, SVM, and RF, with more powerful architectures like EEGNet, ConvLSTM, or Graph Neural Networks (GNNs).

  • Optimize the Transformer model by using EEG-specialized architectures such as TS-Transformer or EEGFormer for better time-series representation.

Enhanced Feature Extraction

  • Incorporate Common Spatial Patterns (CSP) to improve the separation of motor imagery classes.

  • Use Riemannian geometry-based approaches to extract more robust spatial features.

Data Augmentation for EEG

  • Implement synthetic EEG data generation techniques like time-domain warping, frequency shifting, and GAN-based augmentation to improve model generalization.

Online and Transfer Learning

  • Introduce adaptive learning to fine-tune the model based on user-specific EEG patterns.

  • Use few-shot learning or domain adaptation techniques to improve performance across multiple users.