computational-neuroscience

google Apr 23, 2025

Improving brain models with ZAPBench (opens in new tab)

Google Research, in collaboration with HHMI Janelia and Harvard, has introduced ZAPBench, a first-of-its-kind whole-brain activity dataset and benchmark designed to improve the accuracy of brain activity models. Using the larval zebrafish as a model organism, the project provides single-cell resolution recordings of approximately 70,000 neurons, capturing nearly the entire vertebrate brain in action. This resource allows researchers to bridge the gap between structural connectomics and dynamic functional activity to better understand how neural wiring generates complex behavior. ## Whole-Brain Activity in Larval Zebrafish * The dataset focuses on the six-day-old larval zebrafish because it is small, transparent, and capable of complex behaviors like motor learning, hunting, and memory. * Researchers used light-sheet microscopy to scan the brain in 3D slices, recording two hours of continuous activity. * The fish were engineered with GCaMP, a genetically encoded calcium indicator that emits light when neurons fire, allowing for the visualization of real-time neural impulses. * To correlate neural activity with behavior, the fish were placed in a virtual reality environment where stimuli—such as shifting water currents and light changes—were projected around them while tail muscle activity was recorded via electrodes. ## The ZAPBench Framework * ZAPBench standardizes the evaluation of machine learning models in neuroscience, following the tradition of benchmarks in fields like computer vision and language modeling. * The benchmark provides a high-quality dataset of 70,000 neurons, whereas previous efforts in other species often covered less than 0.1% of the brain. * It challenges models to predict how neurons will respond to specific visual stimuli and behavioral patterns. * Initial results presented at ICLR 2025 demonstrate that while simple linear models provide a baseline, advanced architectures like Transformers and Convolutional Neural Networks (CNNs) significantly improve prediction accuracy. ## Integrating Structure and Function * While previous connectomics projects mapped physical neural connections, ZAPBench adds the "dynamic" layer of how those connections are used over time. * The team is currently generating a comprehensive structural connectome for the exact same specimen used in the activity recordings. * This dual approach will eventually allow scientists to investigate the direct relationship between precise physical wiring and the resulting patterns of neural activity across an entire vertebrate brain. By providing an open-source dataset and standardized benchmark, ZAPBench enables the global research community to develop and compare more sophisticated models of neural dynamics, potentially leading to breakthroughs in how we simulate and understand vertebrate cognition.

computational-neuroscience ai machine-learning benchmarking+5

google Mar 20, 2025

Deciphering language processing in the human brain through LLM representations (opens in new tab)

Recent research by Google Research and collaborating universities indicates that Large Language Models (LLMs) process natural language through internal representations that closely mirror neural activity in the human brain. By comparing intracranial recordings from spontaneous conversations with the internal embeddings of the Whisper speech-to-text model, the study found a high degree of linear alignment between artificial and biological language processing. These findings suggest that the statistical structures learned by LLMs via next-word prediction provide a viable computational framework for understanding how humans comprehend and produce speech. ## Mapping LLM Embeddings to Brain Activity * Researchers utilized intracranial electrodes to record neural signals during real-world, free-flowing conversations. * The study compared neural activity against two distinct types of embeddings from the Transformer-based Whisper model: "speech embeddings" from the model’s encoder and "language embeddings" from the decoder. * A linear transformation was used to predict brain signals based on these embeddings, revealing that LLMs and the human brain share similar multidimensional spaces for coding linguistic information. * The alignment suggests that human language processing may rely more on statistical structures and contextual embeddings rather than traditional symbolic rules or syntactic parts of speech. ## Neural Sequences in Speech Comprehension * When a subject listens to speech, the brain follows a specific chronological sequence that aligns with model representations. * Initially, speech embeddings predict cortical activity in the superior temporal gyrus (STG), which is responsible for processing auditory speech sounds. * A few hundred milliseconds later, language embeddings predict activity in Broca’s area (located in the inferior frontal gyrus), marking the transition from sound perception to decoding meaning. ## Reversed Dynamics in Speech Production * During speech production, the neural sequence is reversed, beginning approximately 500 milliseconds before a word is articulated. * Processing starts in Broca’s area, where language embeddings predict activity as the brain plans the semantic content of the utterance. * This is followed by activity in the motor cortex (MC), aligned with speech embeddings, as the brain prepares the physical articulatory movements. * Finally, after articulation, speech embeddings predict activity back in the STG, suggesting the brain is monitoring the sound of the speaker's own voice. This research validates the use of LLMs as powerful predictive tools for neuroscience, offering a new lens through which to study the temporal and spatial dynamics of human communication. By bridging the gap between artificial intelligence and cognitive biology, researchers can better model how the brain integrates sound and meaning in real-time.

computational-neuroscience ai llm nlp+4