---
license: apache-2.0
datasets:
  - Sleep-EDF
  - TUAB
  - MOABB
language:
  - en
tags:
  - eeg
  - brain
  - timeseries
  - self-supervised
  - transformer
  - biomedical
  - neuroscience
---

# BENDR: BErt-inspired Neural Data Representations

Pretrained BENDR model for EEG classification tasks. This is the official Braindecode implementation
of BENDR from Kostas et al. (2021).

## Model Details

- **Model Type**: Transformer-based EEG encoder
- **Pretraining**: Self-supervised learning on masked sequence reconstruction
- **Architecture**: 
  - Convolutional Encoder: 6 blocks with 512 hidden units
  - Transformer Contextualizer: 8 layers, 8 attention heads
  - Total Parameters: ~157M
- **Input**: Raw EEG signals (20 channels, variable length)
- **Output**: Contextualized representations or class predictions

## Usage

```python
from braindecode.models import BENDR
import torch

# Load pretrained model
model = BENDR(n_chans=20, n_outputs=2)

# Load pretrained weights from Hugging Face
from huggingface_hub import hf_hub_download
checkpoint_path = hf_hub_download(repo_id="braindecode/bendr-pretrained-v1", filename="pytorch_model.bin")
checkpoint = torch.load(checkpoint_path)
model.load_state_dict(checkpoint["model_state_dict"], strict=False)

# Use for inference
model.eval()
with torch.no_grad():
    eeg_data = torch.randn(1, 20, 600)  # (batch, channels, time)
    predictions = model(eeg_data)
```

## Fine-tuning

```python
import torch
from torch.optim import Adam

# Freeze encoder for transfer learning
for param in model.encoder.parameters():
    param.requires_grad = False

# Fine-tune on downstream task
optimizer = Adam(model.parameters(), lr=0.0001)
```

## Paper

[BENDR: Using transformers and a contrastive self-supervised learning task to learn from massive amounts of EEG data](https://doi.org/10.3389/fnhum.2021.653659)

Kostas, D., Aroca-Ouellette, S., & Rudzicz, F. (2021).
Frontiers in Human Neuroscience, 15, 653659.

## Citation

```bibtex
@article{kostas2021bendr,
  title={BENDR: Using transformers and a contrastive self-supervised learning task to learn from massive amounts of EEG data},
  author={Kostas, Demetres and Aroca-Ouellette, St{\'e}phane and Rudzicz, Frank},
  journal={Frontiers in Human Neuroscience},
  volume={15},
  pages={653659},
  year={2021},
  publisher={Frontiers}
}
```

## Implementation Notes

- Start token is correctly extracted at index 0 (BERT [CLS] convention)
- Uses T-Fixup weight initialization for stability
- Includes LayerDrop for regularization
- All architectural improvements from original paper maintained

## License

Apache 2.0

## Authors

- Braindecode Team
- Original paper: Kostas et al. (2021)