Efficient Multi Subject Visual Reconstruction from fMRI Using Aligned Representations
Christos Zangos, Danish Ebadulla, Thomas Christopher Sprague, Ambuj Singh

TL;DR
This paper presents a new method for reconstructing visual images from fMRI data by aligning brain signals into a common, subject-agnostic space, improving efficiency and robustness especially with limited data.
Contribution
The work introduces a novel subject-agnostic common representation space for fMRI-based image reconstruction, enabling efficient alignment and transfer across subjects.
Findings
Effective in low-data scenarios
Subject and dataset-agnostic common space
Outperforms traditional end-to-end methods
Abstract
This work introduces a novel approach to fMRI-based visual image reconstruction using a subject-agnostic common representation space. We show that the brain signals of the subjects can be aligned in this common space during training to form a semantically aligned common brain. This is leveraged to demonstrate that aligning subject-specific lightweight modules to a reference subject is significantly more efficient than traditional end-to-end training methods. Our approach excels in low-data scenarios. We evaluate our methods on different datasets, demonstrating that the common space is subject and dataset-agnostic.
Peer Reviews
Decision·Submitted to ICLR 2026
**Originality & Significance:** The paper's primary contribution is significant. While prior work (e.g., MindEye2) has used common spaces, this paper is the first to argue why this is insufficient and to propose explicitly aligning subjects within that space. The central hypothesis, that subject representations are structurally similar but not semantically aligned, is novel and well-motivated. The "AAMax" two-stage training paradigm is a clever and effective solution. This work directly tackles
**Comparison to Highly Related Work:** The paper fails to discuss the differences with MindBridge (Wang et al., 2024) in the main text or related work (Appendix A, where it's missing). MindBridge's structure is even simpler than MindEye (no diffusion prior), which should be a good architecture for verifying the architecture-agnostic property. It also proposed a cross-subject training algorithm and raised the issue of low data availability for new subjects. Therefore, not discussing this highly r
The paper attempts to address the low data efficiency issue in fMRI visual reconstruction, which is a practically significant problem in the field. The combination of adapter alignment and submodular greedy image selection shows some engineering ingenuity in optimizing data utilization.
1. Unreasonable and Unfair Dataset Split: The authors modified the standard training-test split of the NSD dataset, moving shared images from the test set to the training set to achieve a one-to-one image mapping across subjects. This operation lacks a valid justification and is unfair. In fact, semantic alignment can be fully achieved through similar images rather than identical ones. 2. Inconsistent Baseline Results Undermine Fair Comparison: The reported MindEye2 baseline results in this pape
- The paper is very well written, easy to follow and understand. - The motivation for the method and the underlying 'common subject-space hypothesis' is explicitly given and well detailed. - The authors show that their alignment method still works even when a common set of images for all subjects is missing (i.e application to the THINGS-fMRI dataset) - The method of analysis is clear, sound and generalises across two different types of MindEye architectures. - The set of ablations presented is
- Although the experiments are run with different seedings and subjects, then averaged, error bars / confidence intervals are missing. Adding them would enhance the impact / strength of these results. - There are already several studies on fine-tuning a reference model on new subjects and the present paper mostly refers only to the common-space subject-module / adapter of MindEye1/2, hence this very specific improvement related to aligning subject spaces in MindEye architectures can be seen rath
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Taxonomy
TopicsMedical Image Segmentation Techniques · Advanced Vision and Imaging · Image Processing Techniques and Applications
