BrainBind: Bridging Synchronized EEG and fMRI through Long-Form Naturalistic Video Representations
Organizations: School of Computer Science, Center for Human Brain Health, University of Birmingham, UK · School of Computer Science, University of Leeds, UK
Abstract
Real-world vision is dynamic and scene-rich, while EEG and fMRI resolve it at complementary temporal and spatial scales. Most neural decoding systems, however, align one modality in isolation and mostly against static images or short clips. We study the synchronized case: EEG and fMRI are recorded during the same long-form naturalistic viewing, giving a shared stimulus but also recurring narrative context and many semantically similar candidates. We present BrainBind, a framework that maps synchronized EEG and fMRI into frozen long-form video embedding spaces and treats those spaces as common visual-semantic references, not literal neural codes. On CineBrain, a five-seed Recall@K 2 x 4 matrix across two video anchors and four system configurations shows distinct retrieval profiles. With Omni, fMRI organizes the full candidate list most strongly (MRR = 23.82, nDCG@10 = 25.31), while Joint-Dual gives the highest mean label-aware R@1 (13.52%) with a distinct rank-wide profile. The complementary episode-disjoint evaluation quantifies the contribution of repeated stimulus identity and narrative context to the random split. Across these experiments, proxy choice and system configuration produce distinct top-rank and rank-wide retrieval profiles within the present synchronized dataset. The code is available at https://github.com/Forainest789/Brainbind.
Figures & tables
| Experiment family | Backbone | Total parameters |
|---|---|---|
| EEG / fMRI / Both, Omni | Transformer [ 36 ] | 49,907,712 |
| EEG / fMRI / Both, ImageBind | Transformer [ 36 ] | 47,809,536 |
| Joint-Dual, Omni | 2 S4AE (structured SSM) [ 15 ] | 293,835,134 |
| Joint-Dual, ImageBind | 2 S4AE (structured SSM) [ 15 ] | 191,595,902 |
| EEG S4AE-matched, Omni | S4AE (structured SSM) [ 15 ] | 118,541,167 |
| fMRI S4AE-matched, Omni | S4AE (structured SSM) [ 15 ] | 118,541,167 |
| Experiment | Runs | Avg. epochs | Speed (it/s) | Duration (min/run) | Best val mean R@1 (%) |
|---|---|---|---|---|---|
| EEG–Omni Transformer | 5 | 50.0 | 0.067 | 103.50 | 5.17 |
| fMRI–Omni Transformer | 5 | 50.0 | 0.082 | 83.14 | 22.33 |
| Both–Omni Transformer | 5 | 50.0 | 0.063 | 111.30 | 20.69 |
| Joint-Dual–Omni 2 S4AE | 5 | 50.0 | 0.012 | 585.22 | 16.54 |
| EEG–Omni S4AE-matched | 5 | 24.4 | 0.041 | 82.44 | 1.10 |
| fMRI–Omni S4AE-matched | 5 | 46.8 | 0.027 | 357.98 | 16.76 |
| Anchor | Input | R@1 | R@5 | R@10 | R@20 |
|---|---|---|---|---|---|
| Omni | EEG | 1.51 0.13 | 6.09 0.90 | 11.26 1.55 | 20.16 1.82 |
| Omni | fMRI | 9.81 0.16 | 27.70 0.64 | 42.71 0.31 | 59.85 0.53 |
| Omni | Both | 8.41 0.30 | 25.08 0.40 | 39.34 0.41 | 56.04 0.69 |
| Omni | J-Dual | 10.28 0.24 | 17.47 0.54 | 24.20 1.17 | 33.35 1.78 |
| ImageBind | EEG | 0.65 0.05 | 2.61 0.11 | 4.77 0.13 | 9.23 0.26 |
| ImageBind | fMRI | 3.90 0.42 | 12.90 0.82 | 20.97 1.03 | 32.68 0.86 |
| Anchor | Input | Fusion | Backbone | R@1 | MRR | mAP | nDCG@10 |
|---|---|---|---|---|---|---|---|
| Omni | EEG | single | Transformer | 1.91 0.28 | 6.60 0.58 | 6.03 0.49 | 6.06 0.75 |
| Omni | fMRI | single | Transformer | 12.71 0.24 | 23.82 0.29 | 21.37 0.19 | 25.31 0.20 |
| Omni | Both | cross-attn | Dual-Transformer | 11.23 0.30 | 21.91 0.18 | 19.61 0.11 | 23.22 0.20 |
| Omni | J-Dual | mean | 2 S4AE | 13.52 0.11 | 18.69 0.35 | 15.09 0.39 | 16.52 0.51 |
| ImageBind | EEG | single | Transformer | 0.61 0.05 | 2.83 0.06 † | 2.71 0.06 † | 2.20 0.06 † |
| ImageBind | fMRI | single | Transformer | 6.12 0.52 | 13.27 0.67 | 11.41 0.53 | 12.99 0.72 |
| Comparison | Metric | pp | Interpretation | |
|---|---|---|---|---|
| Both vs. fMRI (Omni) | mean R@1 | -1.48 | 0.0012 | System-level difference |
| Both vs. fMRI (Omni) | nDCG@10 | -2.09 | Rank-structure difference | |
| J-Dual vs. fMRI (Omni) | mean R@1 | +0.81 | 0.0008 | Top-rank difference |
| J-Dual vs. fMRI (Omni) | MRR | -5.13 | Rank-organization difference | |
| J-Dual vs. fMRI (Omni) | mAP | -6.28 | Candidate-space difference | |
| J-Dual vs. fMRI (Omni) | nDCG@10 | -8.79 | Rank-structure difference |
| Objective | R@1 | R@5 | R@10 | R@20 | MRR | mAP |
|---|---|---|---|---|---|---|
| InfoNCE, contrastive-only | 0.080 0.025 | 0.345 0.047 | 0.532 0.078 | 0.977 0.105 | 0.393 0.028 | 0.343 0.009 |
| SupCon, contrastive-only | 0.111 0.038 | 0.448 0.008 | 0.782 0.047 | 1.258 0.088 | 0.477 0.023 | 0.376 0.030 |
| InfoNCE, reconstruction-assisted | 0.080 0.025 | 0.316 0.074 | 0.689 0.103 | 1.175 0.171 | 0.435 0.057 | 0.391 0.020 |
| SupCon, reconstruction-assisted | 0.136 0.072 | 0.399 0.098 | 0.648 0.167 | 1.052 0.161 | 0.464 0.081 | 0.375 0.028 |
| R@1 | R@5 | R@10 | R@20 | MRR | mAP | |
|---|---|---|---|---|---|---|
| 0.01 | 0.087 0.009 | 0.370 0.027 | 0.777 0.062 | 1.350 0.124 | 0.465 0.007 | 0.387 0.024 |
| 0.05 | 0.180 0.058 | 0.486 0.034 | 0.936 0.085 | 1.674 0.115 | 0.614 0.025 | 0.486 0.036 |
| 0.10 | 0.098 0.035 | 0.322 0.066 | 0.746 0.103 | 1.394 0.180 | 0.465 0.090 | 0.370 0.066 |
| 0.20 | 0.123 0.041 | 0.396 0.085 | 0.671 0.027 | 1.168 0.120 | 0.471 0.003 | 0.367 0.063 |
| Setting | Split / pool | s2v@1 | v2s@1 | Mean R@1 | MRR | nDCG@10 |
|---|---|---|---|---|---|---|
| Label-aware theoretical chance | 6480 | 0.026 | 0.026 | 0.026 | 0.222 | 0.081 |
| Random brain, Omni | 6480 | 0.015 | 0.015 | 0.015 | 0.149 | 0.052 |
| Shuffled video, Omni | 6480 | 0.000 | 0.000 | 0.000 | 0.125 | 0.045 |
| Random brain, ImageBind | 6480 | 0.015 | 0.000 | 0.008 | 0.151 | 0.052 |
| Shuffled video, ImageBind | 6480 | 0.000 | 0.000 | 0.000 | 0.129 | 0.054 |
| Model | Subject | R@1 | R@5 | R@10 | R@20 | MRR | mAP |
|---|---|---|---|---|---|---|---|
| fMRI–Omni | sub-0001 | 5.234 5.239 | 16.501 13.148 | 24.103 15.745 | 31.956 14.967 | 11.083 8.145 | 11.085 8.146 |
| fMRI–Omni | sub-0002 | 0.050 0.037 | 0.197 0.053 | 0.367 0.093 | 0.768 0.157 | 0.288 0.061 | 0.288 0.061 |
| J-Dual–Omni | sub-0001 | 24.150 1.944 | 42.934 1.379 | 47.909 0.725 | 49.792 0.241 | 32.203 1.652 | 32.203 1.653 |
| J-Dual–Omni | sub-0002 | 0.069 0.012 | 0.274 0.059 | 0.505 0.120 | 0.860 0.194 | 0.320 0.019 | 0.320 0.019 |
| Anchor | Input | Probe | R@1 | s2v@1 | v2s@1 | s2v@5 | v2s@5 | s2v@10 | v2s@10 |
|---|---|---|---|---|---|---|---|---|---|
| ImageBind | EEG | Linear | 0.55 | 0.50 | 0.60 | 1.15 | 1.90 | 2.05 | 3.80 |
| Omni | EEG | Linear | 1.05 | 0.95 | 1.15 | 3.20 | 3.65 | 6.20 | 5.60 |
| ImageBind | EEG | MLP | 0.80 | 0.80 | 0.80 | 2.45 | 2.30 | 3.00 | 4.00 |
| Omni | EEG | MLP | 1.23 | 1.15 | 1.30 | 4.05 | 4.55 | 6.80 | 7.35 |
| ImageBind | fMRI | MLP | 18.58 | 17.20 | 19.95 | 27.75 | 35.45 | 34.30 | 43.15 |
| Omni | fMRI | MLP | 22.85 | 20.60 | 25.10 | 47.25 | 52.30 | 58.40 | 64.95 |
| Model | R@1 | R@5 | R@10 | R@20 | |
|---|---|---|---|---|---|
| Chance floor | – | 0.069 | 0.347 | 0.693 | 1.381 |
| EEG | 3 | 0.075 0.029 | 0.363 0.109 | 0.579 0.182 | 1.224 0.323 |
| fMRI | 3 | 0.129 0.073 | 0.417 0.250 | 0.908 0.244 | 1.641 0.373 |
| Both | 3 | 0.126 0.093 | 0.453 0.200 | 0.893 0.462 | 1.402 0.585 |
| J-Dual | 3 | 0.216 0.051 | 0.615 0.083 | 1.026 0.109 | 1.988 0.054 |
| Anchor / input | Direction | R@1 | R@5 | R@10 | R@20 | |
|---|---|---|---|---|---|---|
| Omni / J-Dual | s2v | 3 | 10.08 0.32 | 17.44 0.51 | 22.96 1.13 | 30.92 1.25 |
| Omni / J-Dual | v2s | 3 | 18.68 0.42 | 27.14 0.81 | 35.06 1.47 | 44.98 2.04 |
| ImageBind / EEG | s2v | 5 | 0.09 0.06 | 0.30 0.09 | 0.51 0.10 | 0.95 0.18 |
| ImageBind / EEG | v2s | 5 | 0.20 0.03 | 0.82 0.07 | 1.49 0.11 | 2.69 0.30 |
| Anchor | Input | Fusion | Configuration | Mean R@1 | MRR | mAP | nDCG@10 | |
|---|---|---|---|---|---|---|---|---|
| Omni | J-Dual | mean | reduced S4AE, contrastive | 3 | 14.38 0.35 | 19.14 0.56 | 15.28 0.52 | 16.89 0.66 |
| ImageBind | EEG | single | S4AE + reconstruction | 5 | 0.15 0.03 | 0.59 0.05 | 0.50 0.04 | 0.39 0.04 |
| Control | s2v@1 | s2v@5 | s2v@10 | s2v@20 | v2s@1 | v2s@5 | v2s@10 | v2s@20 |
|---|---|---|---|---|---|---|---|---|
| One-to-one theoretical chance | 0.015 | 0.077 | 0.154 | 0.309 | 0.015 | 0.077 | 0.154 | 0.309 |
| Label-aware theoretical chance | 0.026 | 0.131 | 0.262 | 0.523 | 0.026 | 0.131 | 0.262 | 0.523 |
| Label-aware random brain | 0.015 | 0.046 | 0.077 | 0.123 | 0.015 | 0.093 | 0.139 | 0.401 |
| Shuffled video features | 0.000 | 0.062 | 0.108 | 0.262 | 0.000 | 0.046 | 0.123 | 0.355 |
| Control | s2v@1 | s2v@5 | s2v@10 | s2v@20 | v2s@1 | v2s@5 | v2s@10 | v2s@20 |
|---|---|---|---|---|---|---|---|---|
| One-to-one theoretical chance | 0.015 | 0.077 | 0.154 | 0.309 | 0.015 | 0.077 | 0.154 | 0.309 |
| Label-aware theoretical chance | 0.026 | 0.131 | 0.262 | 0.523 | 0.026 | 0.131 | 0.262 | 0.523 |
| Label-aware random brain | 0.015 | 0.062 | 0.139 | 0.278 | 0.000 | 0.077 | 0.108 | 0.231 |
| Shuffled video features | 0.000 | 0.031 | 0.077 | 0.293 | 0.000 | 0.108 | 0.231 | 0.309 |
| Anchor | Control | Mean R@1 | Mean MRR | Mean mAP | Mean nDCG@10 |
|---|---|---|---|---|---|
| Omni | Label-aware theoretical chance | 0.026 | 0.222 | 0.155 | 0.081 |
| Omni | Label-aware random brain | 0.015 | 0.149 | 0.148 | 0.052 |
| Omni | Shuffled video features | 0.000 | 0.125 | 0.125 | 0.045 |
| ImageBind | Label-aware theoretical chance | 0.026 | 0.222 | 0.155 | 0.081 |
| ImageBind | Label-aware random brain | 0.008 | 0.151 | 0.154 | 0.052 |
| ImageBind | Shuffled video features | 0.000 | 0.129 | 0.129 | 0.054 |
| Input | Probe | Mean R@1 | s2v@1 | v2s@1 | s2v@5 | v2s@5 | s2v@10 | v2s@10 |
|---|---|---|---|---|---|---|---|---|
| EEG | Linear | 0.32 | 0.29 | 0.35 | 1.02 | 1.68 | 1.87 | 2.87 |
| EEG | MLP | 0.40 | 0.29 | 0.51 | 1.36 | 2.28 | 2.27 | 3.60 |
| Study / family | Signal | Stimulus / supervision | Output target | Scale interpretation |
|---|---|---|---|---|
| MindEye2 [ 32 ] | fMRI | NSD static natural images | Image retrieval and diffusion reconstruction | Strong low-data static-image reference; the target is an image embedding/generator, not video dynamics. |
| MinD-Video [ 7 ] | fMRI | Dynamic visual stimuli | Video reconstruction | Direct fMRI-to-video generation reference; it does not study synchronized EEG–fMRI proxy retrieval. |
| NeuroClips [ 14 ] | fMRI | Natural video clips | Smooth fMRI-to-video reconstruction | High-fidelity video-generation reference optimized for perceptual synthesis, not full-split ranking. |
| Brain Netflix [ 9 ] | fMRI | Scaled natural video viewing | Video reconstruction from brain activity | Closest large-scale video-generation reference; it focuses on fMRI synthesis and data scaling. |
| Animate Your Thoughts / Mind-Animator [ 29 ] | fMRI | Dynamic natural vision | Decoupled video reconstruction | Recent fMRI-to-video generation reference; its target is reconstruction, not shared EEG–fMRI retrieval geometry. |
| BrainBind (ours) | EEG + fMRI | CineBrain long-form naturalistic video | Bidirectional retrieval, proxy diagnostics, and retrieval-conditioned visualization | Studies whether synchronized EEG and fMRI can be organized in one frozen long-form video reference geometry. |
| Model | Held-out subject | Seed | Pairs | Mean R@1 | R@5 | R@10 | R@20 | MRR | mAP |
|---|---|---|---|---|---|---|---|---|---|
| fMRI–Omni | sub-0001 | 42 | 4321 | 11.247 | 31.486 | 41.865 | 48.554 | 20.368 | 20.372 |
| fMRI–Omni | sub-0001 | 123 | 4321 | 2.800 | 11.120 | 18.584 | 27.829 | 7.737 | 7.738 |
| fMRI–Omni | sub-0001 | 456 | 4321 | 1.655 | 6.897 | 11.861 | 19.486 | 5.145 | 5.145 |
| fMRI–Omni | sub-0002 | 42 | 4320 | 0.035 | 0.185 | 0.359 | 0.671 | 0.270 | 0.270 |
| fMRI–Omni | sub-0002 | 123 | 4320 | 0.093 | 0.255 | 0.463 | 0.949 | 0.356 | 0.356 |
| fMRI–Omni | sub-0002 | 456 | 4320 | 0.023 | 0.150 | 0.278 | 0.683 | 0.237 | 0.237 |
| Property | Value |
|---|---|
| GPUs | 2 NVIDIA A100 80GB PCIe |
| GPU memory | 80 GB per GPU |
| CUDA | 12.1 |
| cuDNN | 90100 |
| PyTorch | 2.5.1+cu121 |
| Launch style | accelerate launch --num_processes=2 |
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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