🧠 How does the brain process language? 🧠

We’ve been studying how to scalably answer this question using LLMs and large-scale brain-imaging datasets. Together, these let us automatically generate and test scientific hypotheses about language processing in the brain, potentially enabling a new paradigm for scientific research. This repo contains code for running these analyses.

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References

This repo contains code underlying 2 neuroscience studies:

Generative causal testing to bridge data-driven models and scientific theories in language neuroscience (Antonello*, Singh*, et al., 2026, Nature neuroscience)

Generative causal testing (GCT) is a framework for generating concise explanations of language selectivity in the brain from predictive models and then testing those explanations in follow-up experiments using LLM-generated stimuli.

Evaluating scientific theories as predictive models in language neuroscience (Singh*, Antonello*, et al. 2025, bioRxiv)

QA encoding models builds features by annotating a language stimulus with the answers to yes-no questions using an LLM.

This repo also contains code for experiments in 3 ML studies (for a simple scikit-learn interface to use these, see imodelsX):

Aug-imodels: Augmenting interpretable models with large language models during training (Singh et al. 2023, Nature communications)

Aug-imodels is a framework for LLMs to build extremely efficient and interpretable prediction models, e.g. linear ngram models or decision trees. Aug-imodels use LLMs during fitting but not during inference, allowing complete transparency and dramatic speed improvements.

QA-Emb: Crafting interpretable embeddings by asking LLMs questions (Benara*, Singh*, et al. 2024, NeurIPS)

QA-Emb is a more general version of QA encoding models, that generally builds text embeddings by asking LLMs a series of yes/no questions.

SASC: Explaining black box text modules in natural language with language models (Singh*, Hsu*, et al. 2023, NeurIPS workshop)

SASC is a pipeline for generating natural language explanations of black-box text modules using LLMs and synthetic causal testing.

Finally, here are 3 studies that share the codebase here:

Interpretable embeddings of speech enhance and explain brain encoding performance of audio models (Shimizu et al. 2025, arXiv)

Using QA-Encoding models to analyze and improve black-box speech encoding models.

Interpretable next-token prediction via the generalized induction head(Kim*, Mantena*, et al. 2025, NeurIPS)

Hand-engineering an induction head to retrieve features from the context can help improve interpretable fMRI encoding models.

Vector-ICL: In-context learning with continuous vector representations (Zhuang et al. 2025, ICLR)

Can convert fMRI responses to continuous vector representations that can be used with LLMs to do few-shot decoding of QA features.

Setting up

Dataset

• To quickstart, just download the responses / wordsequences for 3 subjects from the encoding scaling laws paper
  • This is all the data you need if you only want to analyze 3 subjects and don't want to make flatmaps
• To run full experiments, go through the paths in neuro/config.py and download data to the appropriate locations from this box folder
  • To download the main dataset here (the HuthLab fMRI passive listening dataset), run python experiments/00_load_dataset.py (will download the data using datalad)
• To make flatmaps, need to set pycortex filestore to {root_dir}/ds003020/derivative/pycortex-db/
• The data/decoding folder contains a quickstart easy example for TR-level decoding
  • It has everything needed, but if you want to visualize the results on a flatmap, you need to download the relevant PCs from here

Code

• Install using uv. Clone the repo, cd into the repo, run uv add git+https://github.com/csinva/imodelsX, then run uv sync. This will locally install the neuro package
• Useful functions
  • Loading responses
    • neuro.data.response_utils function load_response
    • Loads responses from at {neuro.config.root_dir}/ds003020/derivative/preprocessed_data/{subject}, where they are stored in an h5 file for each story, e.g. wheretheressmoke.h5
  • Loading stimulus
    • ridge_utils.features.stim_utils function load_story_wordseqs
    • Loads textgrids from {root_dir}/ds003020/derivative/TextGrids, where each story has a TextGrid file, e.g. wheretheressmoke.TextGrid
    • Uses {root_dir}/ds003020/derivative/respdict.json to get the length of each story

Demo

• python experiments/02_fit_encoding.py
  • Running this script with no args runs a simple small run. This script takes many relevant arguments through argparse to run different experiments

External links

• Big thanks to folks that released open-source brain-imaging datasets, especially the HuthLab fMRI passive listening dataset and the Podcast ECoG dataset
• See related fMRI experiments
• Built from this template