Paper ID

3a6d34a21e9c7344c564dc502e117b6769f10c47


Title

Integrating modality-specific encoders and cross-modal attention in LLMs for enhanced health prediction.


Introduction

Problem Statement

Integrating modality-specific encoders with cross-modal attention mechanisms in large language models will enhance precision and interpretability in health prediction tasks using IMU, ECG, and radar sensor data compared to single-modality models.

Motivation

Existing multimodal health prediction models often overlook the potential of integrating modality-specific encoders with cross-modal attention mechanisms to enhance both prediction accuracy and interpretability. While prior work has explored multimodal fusion and knowledge distillation, these approaches typically focus on either improving accuracy or interpretability, not both. Additionally, many studies do not leverage the full potential of large language models (LLMs) to process and integrate diverse sensor data effectively. This hypothesis addresses the gap by proposing a novel combination of modality-specific encoders and cross-modal attention mechanisms within an LLM framework to simultaneously improve precision and interpretability in health predictions.


Proposed Method

The proposed research explores the integration of modality-specific encoders with cross-modal attention mechanisms in large language models (LLMs) to improve both precision and interpretability in health prediction tasks. The hypothesis suggests that by using specialized encoders for each sensor modality (IMU, ECG, and radar), we can transform raw sensor data into a format compatible with LLMs, enabling these models to process and integrate diverse inputs effectively. Cross-modal attention mechanisms will be employed to capture correlations between different data modalities, allowing the model to focus on relevant features across modalities. This approach is expected to enhance precision by providing a comprehensive view of the patient's health state and improve interpretability by offering insights into how different modalities contribute to the final prediction. The integration of these components addresses gaps in existing research by leveraging the strengths of LLMs in processing multimodal data and providing a balanced approach to accuracy and interpretability. The evaluation will involve comparing the proposed method against baseline single-modality models and assessing improvements in precision and interpretability using standard metrics.

Background

Modality-Specific Encoders: Modality-specific encoders are designed to convert non-textual data, such as IMU, ECG, and radar signals, into a format that LLMs can process. These encoders handle specific types of input data, transforming them into embeddings that align with the LLM's text-based input space. This approach allows LLMs to process and integrate multimodal data effectively, enhancing their ability to make predictions based on diverse inputs. The implementation involves training encoders on specific data modalities and integrating them into the LLM framework. The baseline comparator would be an LLM without these encoders, which would struggle to process non-textual data.

Cross-Modal Attention Mechanisms: Cross-modal attention mechanisms enable LLMs to capture correlations between different data modalities, such as text and time-series data. This involves using attention layers that focus on relevant parts of each modality, allowing the model to integrate information effectively. The implementation typically involves adding attention layers to the LLM architecture, which are trained to align and fuse information from different modalities. This approach is particularly useful for tasks that require understanding the relationship between textual descriptions and physiological signals. The baseline comparator would be traditional LLMs that do not incorporate cross-modal attention, which may not perform as well in integrating diverse data types.

Implementation

The proposed method involves several key steps. First, modality-specific encoders will be developed for each sensor type (IMU, ECG, and radar) to transform raw sensor data into embeddings compatible with the LLM's text-based input space. These encoders will be trained using datasets that include paired sensor-language data, ensuring that the model can generalize to various scenarios. Next, cross-modal attention mechanisms will be integrated into the LLM architecture to capture correlations between different data modalities. These attention layers will focus on relevant features across modalities, allowing the model to integrate diverse data types effectively. The LLM will then process the integrated data to make health predictions, leveraging its ability to understand complex relationships between modalities. The outputs will be evaluated for precision and interpretability, comparing the proposed method against baseline single-modality models. The integration of modality-specific encoders and cross-modal attention mechanisms is expected to enhance both prediction accuracy and interpretability, providing a comprehensive view of the patient's health state.


Experiments Plan

Operationalization Information

Please implement a multimodal health prediction system that integrates modality-specific encoders with cross-modal attention mechanisms in large language models (LLMs). This experiment will test the hypothesis that such integration enhances both precision and interpretability in health prediction tasks using IMU, ECG, and radar sensor data compared to single-modality models.

Experiment Structure

Implement a global variable PILOT_MODE with three possible settings: 'MINI_PILOT', 'PILOT', or 'FULL_EXPERIMENT'. The experiment should first run in MINI_PILOT mode, then PILOT mode if successful, but stop before FULL_EXPERIMENT (which would require manual verification and approval).

Dataset

Use a multimodal health dataset containing synchronized IMU, ECG, and radar sensor data with corresponding health labels. For the pilot experiments, you can use a publicly available dataset like WESAD (Wearable Stress and Affect Detection) or PAMAP2 (Physical Activity Monitoring), adapting it to include the required modalities if needed.

Model Architecture

Implement the following components:

  1. Modality-specific encoders:
  2. IMU Encoder: A 1D CNN or Transformer-based encoder to process accelerometer and gyroscope data
  3. ECG Encoder: A specialized 1D CNN or RNN encoder designed for ECG signal processing
  4. Radar Encoder: A 2D CNN or 3D CNN encoder for processing radar data

  1. Cross-modal attention mechanism:
  2. Implement a cross-attention layer that allows each modality to attend to features from other modalities
  3. Use a multi-head attention mechanism similar to transformer architectures
  4. Ensure the attention weights are accessible for later interpretability analysis

  1. LLM integration:
  2. Use a pre-trained language model (e.g., BERT, RoBERTa, or a smaller variant for the pilot)
  3. Adapt the LLM to accept the encoded multimodal features
  4. Implement a classification head on top of the LLM for health prediction tasks

Baseline Models

Implement the following baseline models for comparison:

  1. Single-modality models:
  2. IMU-only model: Using only the IMU encoder and a classification head
  3. ECG-only model: Using only the ECG encoder and a classification head
  4. Radar-only model: Using only the radar encoder and a classification head

  1. Simple fusion model:
  2. Concatenate features from all modality encoders without cross-attention
  3. Feed the concatenated features directly to the classification head

Training Procedure

  1. Preprocess the data for each modality:
  2. Normalize and segment the time-series data
  3. Apply appropriate filtering techniques for each sensor type
  4. Align the data temporally across modalities

  1. Train the modality-specific encoders separately on their respective data types

  1. Train the full multimodal model with cross-attention:
  2. Initialize with the pre-trained encoders
  3. Fine-tune the entire architecture end-to-end
  4. Use appropriate loss functions for the health prediction task (e.g., binary/multi-class cross-entropy)

  1. Train the baseline models using the same training procedure and hyperparameters where applicable

Evaluation

  1. Prediction accuracy metrics:
  2. Precision, recall, and F1-score for each model
  3. ROC-AUC and PR-AUC curves
  4. Confusion matrices

  1. Interpretability evaluation:
  2. Implement SHAP (SHapley Additive exPlanations) to analyze feature importance across modalities
  3. Visualize attention weights from the cross-modal attention mechanism
  4. Compute modality contribution scores to quantify how much each modality contributes to predictions

  1. Statistical analysis:
  2. Perform paired t-tests or Wilcoxon signed-rank tests to compare model performances
  3. Calculate confidence intervals for performance metrics
  4. Conduct bootstrap resampling to assess the statistical significance of performance differences

Experiment Output

Generate a comprehensive report including:

  1. Model architecture details and hyperparameters
  2. Training and validation curves
  3. Performance metrics for all models (experimental and baselines)
  4. Interpretability visualizations and analyses
  5. Statistical significance of results
  6. Discussion of findings and limitations

Ensure all code is well-documented and modular to facilitate future extensions. Log all experimental details, including random seeds, to ensure reproducibility.

Please run the experiment first in MINI_PILOT mode to verify the implementation, then in PILOT mode to assess preliminary results. Stop before running the FULL_EXPERIMENT mode, as this will require manual verification of the pilot results.

End Note:

The source paper is Paper 0: Health-LLM: Large Language Models for Health Prediction via Wearable Sensor Data (78 citations, 2024). This idea draws upon a trajectory of prior work, as seen in the following sequence: Paper 1 --> Paper 2 --> Paper 3 --> Paper 4. The progression of research from the source paper to the related papers highlights the evolving role of LLMs in interpreting sensor data for health and activity recognition. Each paper builds on the previous by addressing specific challenges, such as semantic context alignment and cross-modal integration, while expanding the application of LLMs to new sensor modalities. A novel research idea could further advance this field by exploring the integration of multiple sensor modalities to enhance health prediction capabilities, addressing the limitations of single-modality approaches and leveraging the strengths of LLMs in cross-modal understanding.
The initial trend observed from the progression of related work highlights a consistent research focus. However, the final hypothesis proposed here is not merely a continuation of that trend — it is the result of a deeper analysis of the hypothesis space. By identifying underlying gaps and reasoning through the connections between works, the idea builds on, but meaningfully diverges from, prior directions to address a more specific challenge.


References

  1. Health-LLM: Large Language Models for Health Prediction via Wearable Sensor Data (2024)
  2. HARGPT: Are LLMs Zero-Shot Human Activity Recognizers? (2024)
  3. SensorLLM: Aligning Large Language Models with Motion Sensors for Human Activity Recognition (2024)
  4. RadarLLM: Empowering Large Language Models to Understand Human Motion from Millimeter-wave Point Cloud Sequence (2025)
  5. How to Talk to Your Classifier: Conditional Text Generation with Radar–Visual Latent Space (2025)
  6. SensorLM: Learning the Language of Wearable Sensors (2023)
  7. ECG-LM: Understanding Electrocardiogram with a Large Language Model (2023)
  8. Multimodal Foundation Model for Cross-Modal Retrieval and Activity Recognition Tasks (2023)
  9. Multimodal Data Hybrid Fusion and Natural Language Processing for Clinical Prediction Models (2023)
  10. SensorBench: Benchmarking LLMs in Coding-Based Sensor Processing (2024)
  11. Large Language Models are Few-Shot Health Learners (2023)
  12. Employing Multimodal Machine Learning for Stress Detection (2023)
  13. Edge AI Deploying Artificial Intelligence Models on Edge Devices for Real-Time Analytics (2020)
  14. Cross-Modal Health State Estimation (2018)
  15. Multimodal Machine Learning in Precision Health (2022)
  16. Multi Model Data mining approach for Heart failure prediction (2016)
  17. MSKT: multimodal data fusion for improved nursing management in hemorrhagic stroke (2024)
  18. A modular approach to integrating multiple data sources into real-time clinical prediction for pediatric diarrhea (2020)
  19. Large Language models for Time Series Analysis: Techniques, Applications, and Challenges (2025)