HyFI: Hyperbolic Feature Interpolation for Brain-Vision Alignment
Organizations: Department of Artificial Intelligence, Korea University, Seoul, South Korea
Abstract
Recent progress in artificial intelligence has encouraged numerous attempts to understand and decode human visual system from brain signals. These prior works typically align neural activity independently with semantic and perceptual features extracted from images using pre-trained vision models. However, they fail to account for two key challenges: (1) the modality gap arising from the natural difference in the information level of representation between brain signals and images, and (2) the fact that semantic and perceptual features are highly entangled within neural activity. To address these issues, we utilize hyperbolic space, which is well-suited for considering differences in the amount of information and has the geometric property that geodesics between two points naturally bend toward the origin, where the representational capacity is lower. Leveraging these properties, we propose a novel framework, Hyperbolic Feature Interpolation (HyFI), which interpolates between semantic and perceptual visual features along hyperbolic geodesics. This enables both the fusion and compression of perceptual and semantic information, effectively reflecting the limited expressiveness of brain signals and the entangled nature of these features. As a result, it facilitates better alignment between brain and visual features. We demonstrate that HyFI achieves state-of-the-art performance in zero-shot brain-to-image retrieval, outperforming prior methods with Top-1 accuracy improvements of up to +17.3% on THINGS-EEG and +9.1% on THINGS-MEG.
Figures & tables
| Method | Subject 1 | Subject 2 | Subject 3 | Subject 4 | Subject 5 | Subject 6 | Subject 7 | Subject 8 | Subject 9 | Subject 10 | Average | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | |
| Intra-subject: train and test on one subject | ||||||||||||||||||||||
| BraVL | 6.1 | 17.9 | 4.9 | 14.9 | 5.6 | 17.4 | 5.0 | 15.1 | 4.0 | 13.4 | 6.0 | 18.2 | 6.5 | 20.4 | 8.8 | 23.7 | 4.3 | 14.0 | 7.0 | 19.7 | 5.8 | 17.5 |
| NICE | 13.2 | 39.5 | 13.5 | 40.3 | 14.5 | 42.7 | 20.6 | 52.7 | 10.1 | 31.5 | 16.5 | 44.0 | 17.0 | 42.1 | 22.9 | 56.1 | 15.4 | 41.6 | 17.4 | 45.8 | 16.1 | 43.6 |
| ATM-S | 25.6 | 60.4 | 22.0 | 54.5 | 25.0 | 62.4 | 31.4 | 60.9 | 12.9 | 43.0 | 21.3 | 51.1 | 30.5 | 61.5 | 38.8 | 72.0 | 30.4 | 51.5 | 29.1 | 63.5 | 28.5 | 60.4 |
| Cog-cap | 31.4 | 79.7 | 31.4 | 77.8 | 38.2 | 85.7 | 40.4 | 85.8 | 24.4 | 66.3 | 34.8 | 78.8 | 34.7 | 81.0 | 48.1 | 88.6 | 37.4 | 79.4 | 35.6 | 79.3 | 35.6 | 80.2 |
| Method | Subject 1 | Subject 2 | Subject 3 | Subject 4 | Average | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | T-1 | T-5 | |
| Intra-subject: train and test on one subject | ||||||||||
| NICE | 8.7 | 30.5 | 21.8 | 56.6 | 16.5 | 49.7 | 10.3 | 32.3 | 14.3 | 42.3 |
| UBP | 15.0 | 38.0 | 46.0 | 80.5 | 27.3 | 59.0 | 18.5 | 43.5 | 26.7 | 55.2 |
| HyFI | 17.6 | 40.1 | 63.8 | 91.1 | 38.0 | 76.9 | 23.7 | 50.2 | 35.8 | 64.6 |
| Inter-subject: leave one subject out for test | ||||||||||
| Interpolation | Hyperbolic | THINGS-EEG | THINGS-MEG | ||
|---|---|---|---|---|---|
| T-1 | T-5 | T-1 | T-5 | ||
| – | – | 49.4 | 81.0 | 23.1 | 47.8 |
| – | ✓ | 54.3 | 82.5 | 28.8 | 55.1 |
| ✓ | – | 59.7 | 86.8 | 25.2 | 51.8 |
| ✓ | ✓ | 68.2 | 91.9 | 35.8 | 64.6 |
| Method | Architecture | Model | THINGS-EEG | THINGS-MEG | ||
| w/o HyFI | Ours | w/o HyFI | Ours | |||
| CLIP | CNN | RN50 | 49.4 | 68.2 | 23.1 | 35.8 |
| RN101 | 44.4 | 62.1 | 21.0 | 34.8 | ||
| ViT | ViT-B/16 | 36.0 | 41.6 | 18.6 | 23.3 | |
| ViT-B/32 | 42.5 | 46.9 | 20.0 | 25.1 | ||
| ViT-L/14 | 30.1 | 34.1 | 13.0 | 21.0 | ||
| Brain Encoder | THINGS-EEG | THINGS-MEG | ||
|---|---|---|---|---|
| w/o HyFI | Ours | w/o HyFI | Ours | |
| ShallowNet | 36.6 | 50.5 | 15.1 | 23.2 |
| EEGNet | 36.2 | 51.6 | 19.5 | 26.4 |
| TSConv | 41.1 | 57.1 | 21.9 | 30.5 |
| EEGProject | 49.4 | 68.2 | 23.1 | 35.8 |
| Model | Params | Emb dim | Semantic | Perceptual | ||
|---|---|---|---|---|---|---|
| Norm | Std | Norm | Std | |||
| RN50 | 38.32 M | 1024 | 233 | 0.05 | 277 | 0.06 |
| RN101 | 56.26 M | 512 | 282 | 0.09 | 325 | 0.11 |
| ViT/B-16 | 86.19 M | 512 | 1409 | 0.48 | 1404 | 0.48 |
| ViT/B-32 | 87.85 M | 512 | 1447 | 0.49 | 1473 | 0.51 |
| ViT/L-14 | 303.97 M | 768 | 2399 | 0.67 | 2535 | 0.71 |
| Semantic | Perceptual | Top-1 ACC | Top-5 ACC |
|---|---|---|---|
| Original | Fovea blur | 53.8 | 83.7 |
| SAM | 56.6 | 85.4 | |
| Gaussian noise | 61.4 | 89.8 | |
| Low resolution | 63.5 | 89.6 | |
| Gaussian blur | 65.3 | 91.4 | |
| Fovea blur | SAM | 60.5 | 88.5 |
| Input feature | Top-1 ACC | Top-5 ACC |
|---|---|---|
| EEG | 54.5 | 84.8 |
| Perceptual | 67.1 | 91.8 |
| Original | 67.6 | 91.8 |
| Semantic | 68.2 | 91.9 |
| Method | Model | ShallowNet | EEGNet | TSConv | EEGProject | ||||
|---|---|---|---|---|---|---|---|---|---|
| Base | Ours | Base | Ours | Base | Ours | Base | Ours | ||
| CLIP | RN50 | 36.6 | 50.5 | 36.2 | 51.6 | 41.1 | 57.1 | 49.4 | 68.2 |
| RN101 | 34.0 | 45.8 | 35.6 | 46.4 | 35.9 | 53.4 | 44.4 | 62.1 | |
| ViT-B/16 | 28.3 | 36.7 | 30.7 | 35.1 | 31.4 | 40.5 | 36.0 | 41.6 | |
| ViT-B/32 | 30.7 | 36.8 | 33.7 | 37.0 | 36.6 | 40.8 | 42.5 | 46.9 | |
| ViT-L/14 | 19.8 | 22.8 | 19.1 | 27.0 | 20.9 | 27.4 | 30.1 | 34.1 | |
Cross-Modal Alignment
Cross-modal alignment maps representations from different data types into compatible spaces so models can compare, transfer, and combine information.
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