Posts in category: Google AI

Posted by Carlos Esteves and Ameesh Makadia, Research Scientists, Google Research, Athena Team

Typical deep learning models for computer vision, like convolutional neural networks (CNNs) and vision transformers (ViT), process signals assuming planar (flat) spaces. For example, digital images are represented as a grid of pixels on a plane. However, this type of data makes up only a fraction of the data we encounter in scientific applications. Variables sampled from the Earth’s atmosphere, like temperature and humidity, are naturally represented on the sphere. Some kinds of cosmological data and panoramic photos are also spherical signals, and are better treated as such.

Using methods designed for planar images to process spherical signals is problematic for a couple of reasons. First, there is a sampling problem, i.e., there is no way of defining uniform grids on the sphere, which are needed for planar CNNs and ViTs, without heavy distortion.

When projecting the sphere into a plane, the patch represented by the red circle is heavily distorted near the poles. This sampling problem hurts the accuracy of conventional CNNs and ViTs on spherical inputs.

Second, signals and local patterns on the sphere are often complicated by rotations, so models need a way to address that. We would like equivariance to 3D rotations, which ensures that learned features follow the rotations of the input. This leads to better utilization of the model parameters and allows training with less data. Equivariance to 3D rotations is also useful in most settings where inputs don’t have a preferred orientation, such as 3D shapes and molecules.

Drone racing with panoramic cameras. Here the sharp turns result in large 3D rotations of the spherical image. We would like our models to be robust to such rotations. Source: https://www.youtube.com/watch?v=_J7qXbbXY80 (licensed under CC BY)

In the atmosphere, it is common to see similar patterns appearing at different positions and orientations. We would like our models to share parameters to recognize these patterns.

With the above challenges in mind, in “Scaling Spherical CNNs”, presented at ICML 2023, we introduce an open-source library in JAX for deep learning on spherical surfaces. We demonstrate how applications of this library match or surpass state-of-the-art performance on weather forecasting and molecular property prediction benchmarks, tasks that are typically addressed with transformers and graph neural networks.

Background on spherical CNNs

Spherical CNNs solve both the problems of sampling and of robustness to rotation by leveraging spherical convolution and cross-correlation operations, which are typically computed via generalized Fourier transforms. For planar surfaces, however, convolution with small filters is faster, because it can be performed on regular grids without using Fourier transforms. The higher computational cost for spherical inputs has so far restricted the application of spherical CNNs to small models and datasets and low resolution datasets.

Our contributions

We have implemented the spherical convolutions from spin-weighted spherical CNNs in JAX with a focus on speed, and have enabled distributed training over a large number of TPUs using data parallelism. We also introduced a new phase collapse activation and spectral batch normalization layer, and a new residual block that improves accuracy and efficiency, which allows training more accurate models up to 100x larger than before. We apply these new models on molecular property regression and weather forecasting.

We scale spherical CNNs by up to two orders of magnitude in terms of feature sizes and model capacity, compared to the literature: Cohen’18, Esteves’18, Esteves’20, and Cobb’21. VGG-19 is included as a conventional CNN reference. Our largest model for weather forecasting has 256 x 256 x 78 inputs and outputs, and runs 96 convolutional layers during training with a lowest internal resolution of 128 x 128 x 256.

Molecular property regression

Predicting properties of molecules has applications in drug discovery, where the goal is to quickly screen numerous molecules in search of those with desirable properties. Similar models may also be relevant in the design of drugs targeting the interaction between proteins. Current methods in computational or experimental quantum chemistry are expensive, which motivates the use of machine learning.

Molecules can be represented by a set of atoms and their positions in 3D space; rotations of the molecule change the positions but not the molecular properties. This motivates the application of spherical CNNs because of their rotation equivariance. However, molecules are not defined as signals on the sphere so the first step is to map them to a set of spherical functions. We do so by leveraging physics-based interactions between the atoms of the molecule.

Each atom is represented by a set of spherical signals accumulating physical interactions with other atoms of each type (shown in the three panels on the right). For example, the oxygen atom (O; top panel) has a channel for oxygen (indicated by the sphere labeled “O” on the left) and hydrogen (“H”, right). The accumulated Coulomb forces on the oxygen atom with respect to the two hydrogen atoms is indicated by the red shaded regions on the bottom of the sphere labeled “H”. Because the oxygen atom contributes no forces to itself, the “O” sphere is uniform. We include extra channels for the Van der Waals forces.

Spherical CNNs are applied to each atom’s features, and results are later combined to produce the property predictions. This results in state-of-the art performance in most properties as typically evaluated in the QM9 benchmark:

Error comparison against the state-of-the-art on 12 properties of QM9 (see the dataset paper for details). We show TorchMD-Net and PaiNN results, normalizing TorchMD-Net errors to 1.0 (lower is better). Our model, shown in green, outperforms the baselines in most targets.

Weather forecasting

Accurate climate forecasts serve as invaluable tools for providing timely warnings of extreme weather events, enabling effective water resource management, and guiding informed infrastructure planning. In a world increasingly threatened by climate disasters, there is an urgency to deliver forecasts much faster and more accurately over a longer time horizon than general circulation models. Forecasting models will also be important for predicting the safety and effectiveness of efforts intended to combat climate change, such as climate interventions. The current state-of-the-art uses costly numerical models based on fluid dynamics and thermodynamics, which tend to drift after a few days.

Given these challenges, there is an urgency for machine learning researchers to address climate forecasting problems, as data-driven techniques have the potential of both reducing the computational cost and improving long range accuracy. Spherical CNNs are suitable for this task since atmospheric data is natively presented on the sphere. They can also efficiently handle repeating patterns at different positions and orientations that are common in such data.

We apply our models to several weather forecasting benchmarks and outperform or match neural weather models based on conventional CNNs (specifically, 1, 2, and 3). Below we show results in a test setting where the model takes a number of atmospheric variables as input and predicts their values six hours ahead. The model is then iteratively applied on its own predictions to produce longer forecasts. During training, the model predicts up to three days ahead, and is evaluated up to five days. Keisler proposed a graph neural network for this task, but we show that spherical CNNs can match the GNN accuracy in the same setting.

Iterative weather forecasting up to five days (120h) ahead with spherical CNNs. The animations show the specific humidity forecast at a given pressure and its error.

Wind speed and temperature forecasts with spherical CNNs.

Additional resources

Our JAX library for efficient spherical CNNs is now available. We have shown applications to molecular property regression and weather forecasting, and we believe the library will be helpful in other scientific applications, as well as in computer vision and 3D vision.

Weather forecasting is an active area of research at Google with the goal of building more accurate and robust models — like Graphcast, a recent ML-based mid-range forecasting model — and to build tools that enable further advancement across the research community, such as the recently released WeatherBench 2.

Acknowledgements

This work was done in collaboration with Jean-Jacques Slotine, and is based on previous collaborations with Kostas Daniilidis and Christine Allen-Blanchette. We thank Stephan Hoyer, Stephan Rasp, and Ignacio Lopez-Gomez for helping with data processing and evaluation, and Fei Sha, Vivian Yang, Anudhyan Boral, Leonardo Zepeda-Núñez, and Avram Hershko for suggestions and discussions. We are thankful to Michael Riley and Corinna Cortes for supporting and encouraging this project.

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Posted by Shaina Mehta, Program Manager, Google

Google is proud to be a Platinum Sponsor of the International Conference on Computer Vision (ICCV 2023), a premier annual conference, which is being held this week in Paris, France. As a leader in computer vision research, Google has a strong presence at this year’s conference with 60 accepted papers and active involvement in 27 workshops and tutorials. Google is also proud to be a Platinum Sponsor for the LatinX in CV workshop. We look forward to sharing some of our extensive computer vision research and expanding our partnership with the broader research community.

Attending ICCV 2023? We hope you’ll visit the Google booth to chat with researchers who are actively pursuing the latest innovations in computer vision, and check out some of the scheduled booth activities (e.g., demos and Q&A sessions listed below). Visit the @GoogleAI Twitter account to find out more about the Google booth activities at ICCV 2023.

Take a look below to learn more about the Google research being presented at ICCV 2023 (Google affiliations in bold).

Board and Organizing Committee

Google Research booth activities

Accepted papers

Tutorial

Workshops

* Work done while at Google

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Posted by Zhengqi Li and Noah Snavely, Research Scientists, Google Research

A mobile phone’s camera is a powerful tool for capturing everyday moments. However, capturing a dynamic scene using a single camera is fundamentally limited. For instance, if we wanted to adjust the camera motion or timing of a recorded video (e.g., to freeze time while sweeping the camera around to highlight a dramatic moment), we would typically need an expensive Hollywood setup with a synchronized camera rig. Would it be possible to achieve similar effects solely from a video captured using a mobile phone’s camera, without a Hollywood budget?

In “DynIBaR: Neural Dynamic Image-Based Rendering”, a best paper honorable mention at CVPR 2023, we describe a new method that generates photorealistic free-viewpoint renderings from a single video of a complex, dynamic scene. Neural Dynamic Image-Based Rendering (DynIBaR) can be used to generate a range of video effects, such as “bullet time” effects (where time is paused and the camera is moved at a normal speed around a scene), video stabilization, depth of field, and slow motion, from a single video taken with a phone’s camera. We demonstrate that DynIBaR significantly advances video rendering of complex moving scenes, opening the door to new kinds of video editing applications. We have also released the code on the DynIBaR project page, so you can try it out yourself.

Background

The last few years have seen tremendous progress in computer vision techniques that use neural radiance fields (NeRFs) to reconstruct and render static (non-moving) 3D scenes. However, most of the videos people capture with their mobile devices depict moving objects, such as people, pets, and cars. These moving scenes lead to a much more challenging 4D (3D + time) scene reconstruction problem that cannot be solved using standard view synthesis methods.

Other recent methods tackle view synthesis for dynamic scenes using space-time neural radiance fields (i.e., Dynamic NeRFs), but such approaches still exhibit inherent limitations that prevent their application to casually captured, in-the-wild videos. In particular, they struggle to render high-quality novel views from videos featuring long time duration, uncontrolled camera paths and complex object motion.

The key pitfall is that they store a complicated, moving scene in a single data structure. In particular, they encode scenes in the weights of a multilayer perceptron (MLP) neural network. MLPs can approximate any function — in this case, a function that maps a 4D space-time point (x, y, z, t) to an RGB color and density that we can use in rendering images of a scene. However, the capacity of this MLP (defined by the number of parameters in its neural network) must increase according to the video length and scene complexity, and thus, training such models on in-the-wild videos can be computationally intractable. As a result, we get blurry, inaccurate renderings like those produced by DVS and NSFF (shown below). DynIBaR avoids creating such large scene models by adopting a different rendering paradigm.

Image-based rendering (IBR)

A key insight behind DynIBaR is that we don’t actually need to store all of the scene contents in a video in a giant MLP. Instead, we directly use pixel data from nearby input video frames to render new views. DynIBaR builds on an image-based rendering (IBR) method called IBRNet that was designed for view synthesis for static scenes. IBR methods recognize that a new target view of a scene should be very similar to nearby source images, and therefore synthesize the target by dynamically selecting and warping pixels from the nearby source frames, rather than reconstructing the whole scene in advance. IBRNet, in particular, learns to blend nearby images together to recreate new views of a scene within a volumetric rendering framework.

DynIBaR: Extending IBR to complex, dynamic videos

To extend IBR to dynamic scenes, we need to take scene motion into account during rendering. Therefore, as part of reconstructing an input video, we solve for the motion of every 3D point, where we represent scene motion using a motion trajectory field encoded by an MLP. Unlike prior dynamic NeRF methods that store the entire scene appearance and geometry in an MLP, we only store motion, a signal that is more smooth and sparse, and use the input video frames to determine everything else needed to render new views.

We optimize DynIBaR for a given video by taking each input video frame, rendering rays to form a 2D image using volume rendering (as in NeRF), and comparing that rendered image to the input frame. That is, our optimized representation should be able to perfectly reconstruct the input video.

We illustrate how DynIBaR renders images of dynamic scenes. For simplicity, we show a 2D world, as seen from above. (a) A set of input source views (triangular camera frusta) observe a cube moving through the scene (animated square). Each camera is labeled with its timestamp (t-2, t-1, etc). (b) To render a view from camera at time t, DynIBaR shoots a virtual ray through each pixel (blue line), and computes colors and opacities for sample points along that ray. To compute those properties, DyniBaR projects those samples into other views via multi-view geometry, but first, we must compensate for the estimated motion of each point (dashed red line). (c) Using this estimated motion, DynIBaR moves each point in 3D to the relevant time before projecting it into the corresponding source camera, to sample colors for use in rendering. DynIBaR optimizes the motion of each scene point as part of learning how to synthesize new views of the scene.

However, reconstructing and deriving new views for a complex, moving scene is a highly ill-posed problem, since there are many solutions that can explain the input video — for instance, it might create disconnected 3D representations for each time step. Therefore, optimizing DynIBaR to reconstruct the input video alone is insufficient. To obtain high-quality results, we also introduce several other techniques, including a method called cross-time rendering. Cross-time rendering refers to the use of the state of our 4D representation at one time instant to render images from a different time instant, which encourages the 4D representation to be coherent over time. To further improve rendering fidelity, we automatically factorize the scene into two components, a static one and a dynamic one, modeled by time-invariant and time-varying scene representations respectively.

Creating video effects

DynIBaR enables various video effects. We show several examples below.

Video stabilization

We use a shaky, handheld input video to compare DynIBaR’s video stabilization performance to existing 2D video stabilization and dynamic NeRF methods, including FuSta, DIFRINT, HyperNeRF, and NSFF. We demonstrate that DynIBaR produces smoother outputs with higher rendering fidelity and fewer artifacts (e.g., flickering or blurry results). In particular, FuSta yields residual camera shake, DIFRINT produces flicker around object boundaries, and HyperNeRF and NSFF produce blurry results.

Simultaneous view synthesis and slow motion

DynIBaR can perform view synthesis in both space and time simultaneously, producing smooth 3D cinematic effects. Below, we demonstrate that DynIBaR can take video inputs and produce smooth 5X slow-motion videos rendered using novel camera paths.

Video bokeh

DynIBaR can also generate high-quality video bokeh by synthesizing videos with dynamically changing depth of field. Given an all-in-focus input video, DynIBar can generate high-quality output videos with varying out-of-focus regions that call attention to moving (e.g., the running person and dog) and static content (e.g., trees and buildings) in the scene.

Conclusion

DynIBaR is a leap forward in our ability to render complex moving scenes from new camera paths. While it currently involves per-video optimization, we envision faster versions that can be deployed on in-the-wild videos to enable new kinds of effects for consumer video editing using mobile devices.

Acknowledgements

DynIBaR is the result of a collaboration between researchers at Google Research and Cornell University. The key contributors to the work presented in this post include Zhengqi Li, Qianqian Wang, Forrester Cole, Richard Tucker, and Noah Snavely.

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Ramnath Kumar, Pre-Doctoral Researcher, and Arun Sai Suggala, Research Scientist, Google Research

Deep neural networks (DNNs) have become essential for solving a wide range of tasks, from standard supervised learning (image classification using ViT) to meta-learning. The most commonly-used paradigm for learning DNNs is empirical risk minimization (ERM), which aims to identify a network that minimizes the average loss on training data points. Several algorithms, including stochastic gradient descent (SGD), Adam, and Adagrad, have been proposed for solving ERM. However, a drawback of ERM is that it weights all the samples equally, often ignoring the rare and more difficult samples, and focusing on the easier and abundant samples. This leads to suboptimal performance on unseen data, especially when the training data is scarce.

To overcome this challenge, recent works have developed data re-weighting techniques for improving ERM performance. However, these approaches focus on specific learning tasks (such as classification) and/or require learning an additional meta model that predicts the weights of each data point. The presence of an additional model significantly increases the complexity of training and makes them unwieldy in practice.

In “Stochastic Re-weighted Gradient Descent via Distributionally Robust Optimization” we introduce a variant of the classical SGD algorithm that re-weights data points during each optimization step based on their difficulty. Stochastic Re-weighted Gradient Descent (RGD) is a lightweight algorithm that comes with a simple closed-form expression, and can be applied to solve any learning task using just two lines of code. At any stage of the learning process, RGD simply reweights a data point as the exponential of its loss. We empirically demonstrate that the RGD reweighting algorithm improves the performance of numerous learning algorithms across various tasks, ranging from supervised learning to meta learning. Notably, we show improvements over state-of-the-art methods on DomainBed and Tabular classification. Moreover, the RGD algorithm also boosts performance for BERT using the GLUE benchmarks and ViT on ImageNet-1K.

Distributionally robust optimization

Distributionally robust optimization (DRO) is an approach that assumes a “worst-case” data distribution shift may occur, which can harm a model’s performance. If a model has focussed on identifying few spurious features for prediction, these “worst-case” data distribution shifts could lead to the misclassification of samples and, thus, a performance drop. DRO optimizes the loss for samples in that “worst-case” distribution, making the model robust to perturbations (e.g., removing a small fraction of points from a dataset, minor up/down weighting of data points, etc.) in the data distribution. In the context of classification, this forces the model to place less emphasis on noisy features and more emphasis on useful and predictive features. Consequently, models optimized using DRO tend to have better generalization guarantees and stronger performance on unseen samples.

Inspired by these results, we develop the RGD algorithm as a technique for solving the DRO objective. Specifically, we focus on Kullback–Leibler divergence-based DRO, where one adds perturbations to create distributions that are close to the original data distribution in the KL divergence metric, enabling a model to perform well over all possible perturbations.

Figure illustrating DRO. In contrast to ERM, which learns a model that minimizes expected loss over original data distribution, DRO learns a model that performs well on several perturbed versions of the original data distribution.

Stochastic re-weighted gradient descent

Consider a random subset of samples (called a mini-batch), where each data point has an associated loss L_i. Traditional algorithms like SGD give equal importance to all the samples in the mini-batch, and update the parameters of the model by descending along the averaged gradients of the loss of those samples. With RGD, we reweight each sample in the mini-batch and give more importance to points that the model identifies as more difficult. To be precise, we use the loss as a proxy to calculate the difficulty of a point, and reweight it by the exponential of its loss. Finally, we update the model parameters by descending along the weighted average of the gradients of the samples.

Due to stability considerations, in our experiments we clip and scale the loss before computing its exponential. Specifically, we clip the loss at some threshold T, and multiply it with a scalar that is inversely proportional to the threshold. An important aspect of RGD is its simplicity as it doesn’t rely on a meta model to compute the weights of data points. Furthermore, it can be implemented with two lines of code, and combined with any popular optimizers (such as SGD, Adam, and Adagrad.

Figure illustrating the intuitive idea behind RGD in a binary classification setting. Feature 1 and Feature 2 are the features available to the model for predicting the label of a data point. RGD upweights the data points with high losses that have been misclassified by the model.

Results

We present empirical results comparing RGD with state-of-the-art techniques on standard supervised learning and domain adaptation (refer to the paper for results on meta learning). In all our experiments, we tune the clipping level and the learning rate of the optimizer using a held-out validation set.

Supervised learning

We evaluate RGD on several supervised learning tasks, including language, vision, and tabular classification. For the task of language classification, we apply RGD to the BERT model trained on the General Language Understanding Evaluation (GLUE) benchmark and show that RGD outperforms the BERT baseline by +1.94% with a standard deviation of 0.42%. To evaluate RGD’s performance on vision classification, we apply RGD to the ViT-S model trained on the ImageNet-1K dataset, and show that RGD outperforms the ViT-S baseline by +1.01% with a standard deviation of 0.23%. Moreover, we perform hypothesis tests to confirm that these results are statistically significant with a p-value that is less than 0.05.

RGD’s performance on language and vision classification using GLUE and Imagenet-1K benchmarks. Note that MNLI, QQP, QNLI, SST-2, MRPC, RTE and COLA are diverse datasets which comprise the GLUE benchmark.

For tabular classification, we use MET as our baseline, and consider various binary and multi-class datasets from UC Irvine’s machine learning repository. We show that applying RGD to the MET framework improves its performance by 1.51% and 1.27% on binary and multi-class tabular classification, respectively, achieving state-of-the-art performance in this domain.

Domain generalization

To evaluate RGD’s generalization capabilities, we use the standard DomainBed benchmark, which is commonly used to study a model’s out-of-domain performance. We apply RGD to FRR, a recent approach that improved out-of-domain benchmarks, and show that RGD with FRR performs an average of 0.7% better than the FRR baseline. Furthermore, we confirm with hypothesis tests that most benchmark results (except for Office Home) are statistically significant with a p-value less than 0.05.

Performance of RGD on DomainBed benchmark for distributional shifts.

Class imbalance and fairness

To demonstrate that models learned using RGD perform well despite class imbalance, where certain classes in the dataset are underrepresented, we compare RGD’s performance with ERM on long-tailed CIFAR-10. We report that RGD improves the accuracy of baseline ERM by an average of 2.55% with a standard deviation of 0.23%. Furthermore, we perform hypothesis tests and confirm that these results are statistically significant with a p-value of less than 0.05.

Performance of RGD on the long-tailed Cifar-10 benchmark for class imbalance domain.

Limitations

The RGD algorithm was developed using popular research datasets, which were already curated to remove corruptions (e.g., noise and incorrect labels). Therefore, RGD may not provide performance improvements in scenarios where training data has a high volume of corruptions. A potential approach to handle such scenarios is to apply an outlier removal technique to the RGD algorithm. This outlier removal technique should be capable of filtering out outliers from the mini-batch and sending the remaining points to our algorithm.

Conclusion

RGD has been shown to be effective on a variety of tasks, including out-of-domain generalization, tabular representation learning, and class imbalance. It is simple to implement and can be seamlessly integrated into existing algorithms with just two lines of code change. Overall, RGD is a promising technique for boosting the performance of DNNs, and could help push the boundaries in various domains.

Acknowledgements

The paper described in this blog post was written by Ramnath Kumar, Arun Sai Suggala, Dheeraj Nagaraj and Kushal Majmundar. We extend our sincere gratitude to the anonymous reviewers, Prateek Jain, Pradeep Shenoy, Anshul Nasery, Lovish Madaan, and the numerous dedicated members of the machine learning and optimization team at Google Research India for their invaluable feedback and contributions to this work.

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Posted by Michał Januszewski, Research Scientist, Google Research

The human brain is perhaps the most computationally complex machine in existence, consisting of networks of billions of cells. Researchers currently don’t understand the full picture of how glitches in its network machinery contribute to mental illnesses and other diseases, such as dementia. However, the emerging connectomics field, which aims to precisely map the connections between every cell in the brain, could help solve that problem. While maps have only been created for simpler organisms, technological advances for mapping even larger brains can enable us to understand how the human brain works, and how to treat brain diseases.

Today, we’re excited to announce that the Connectomics team at Google Research and our collaborators are launching a $33 million project to expand the frontiers of connectomics over the next five years. Supported by the Brain Research Through Advancing Innovative Neurotechnologies (BRAIN) Initiative at the National Institutes of Health (NIH) and led by researchers at Harvard University, we’ll be working alongside a multidisciplinary team of experts from the Allen Institute, MIT, Cambridge University, Princeton University and Johns Hopkins University, with advisers from HHMI’s Janelia Research Campus. Our project goal is to tackle an immense challenge in neuroscience: mapping a tiny fraction (2-3%) of the mouse brain. We will specifically target the hippocampal region, which is responsible for encoding memories, attention and spatial navigation. This project is one of 11 funded by the NIH’s $150 million BRAIN Initiative Connectivity Across Scales (BRAIN CONNECTS) program. Google Research is contributing computational and analytical resources to this effort, and will not receive any funding from the NIH. Our project asks a critical question: Can we scale and speed up our technologies enough to map the whole connectome of a mouse brain?

The modern era of connectomics

This effort to map the connectome of a small part of the mouse brain builds on a decade of innovation in the field, including many advances initiated by the Connectomics team at Google Research. We hope to accomplish something similar to the early days of the Human Genome Project, when scientists worked for years to sequence a small portion of the human genome as they refined technologies that would enable them to complete the rest of the genome.

In 2021, we and collaborators at Harvard successfully mapped one cubic millimeter of the human brain, which we released as the H01 dataset, a resource for studying the human brain and scaling connectomics technologies. But mapping the entire human brain connectome would require gathering and analyzing as much as a zettabyte of data (one billion terabytes), which is beyond the current capabilities of existing technologies.

Analyzing a mouse connectome is the next best thing. It is small enough to be technically feasible and could potentially deliver insights relevant to our own minds; neuroscientists already use mice to study human brain function and dysfunction. By working together to map 10–15 cubic mm of the mouse brain, we hope to develop new approaches that will allow us to map the entire remainder of the mouse brain, and the human brain thereafter.

Neuroscientists have been working for decades to map increasingly larger and more complicated connectomes.

One of biology’s largest datasets

In this connectomics project, we will map the connectome of the hippocampal formation of the mouse brain, which converts short-term memories into long-term memories and helps the mouse navigate in space. The mouse hippocampal formation is the largest area of any brain we’ve attempted to understand in this way. Through mapping this region of the mouse brain, we will create one of the largest datasets in biology, combining about 25,000 terabytes, or 25 petabytes of brain data. For reference, there are about 250 billion stars in our Milky Way Galaxy. If each of those stars was a single byte, it would take 100,000 Milky Way Galaxies to match the 25 petabytes of data that the project will collect when mapping a small region of the mouse brain.

To illustrate the hippocampal project’s scale, we calculated the number of Pixel phones (shown as stacks of Pixels below) needed to store the image data from the completed connectome projects that mapped the roundworm and fruit fly brains, as well as for the mouse hippocampal region and entire mouse brain projects, which are just getting started.

Then, we compared the heights of each Pixel stack to familiar objects and landmarks. It would take a stack of 100 Pixels, as tall as a four-year-old girl, to store the image data for the fruit fly brain, the largest completed project thus far. In contrast, the mouse hippocampal connectome effort will require storage equivalent to more than 48,800 Pixels, reaching as high as the Empire State Building. The animation below shows how the mouse hippocampal project will surpass the scale of previous connectome projects.

We are partnering with several collaborators to build a connectome (a map of the connections between brain cells) for the hippocampal region of a mouse brain. This project will create the largest connectomic dataset ever, surpassing the scale of previous projects that mapped the smaller roundworm and fruit fly brains. We hope this effort will lead to the development of new approaches that will allow us to later map an entire mouse brain. This animation shows how the field of connectomics is scaling up by calculating the number of Pixel phones needed to store the data from various projects. It would take just two Pixels, the height of an olive, to store the roundworm connectome data, while it would take a stack of Pixels the size of Mount Everest to store the data from an entire mouse connectome.

Understanding the connectome of the mouse hippocampal formation could help illuminate the way our own brains work. For instance, we may find common features between this circuitry in the mouse brain and human brains that explain how we know where we are, how our brains associate memories with specific locations, and what goes wrong in people who can’t properly form new spatial memories.

Opening the petabyte pipeline

Over the last decade, our team has worked to develop tools for managing massive connectomic datasets, and extracting scientific value from them. But a mouse brain has 1,000 times more neurons than the brain of the Drosophila fruit fly, an organism for which we helped build a connectome for a large part of the brain. Starting the mouse brain connectome will challenge us to improve existing technologies to enable us to map more data faster than ever before.

We’ll continue to refine our flood-filling networks, which use deep learning to trace, or “segment”, each neuron’s path through three-dimensional brain volumes made from electron microscope data. We’ll also extend the capabilities of our self-supervised learning technology, SegCLR, which allows us to automatically extract key insights from segmented volumes, such as identifying cell type (e.g., pyramidal neuron, basket neuron, etc.) and parts of each neuron (e.g., axon, dendrite, etc.).

A flood filling network traces a neuron through three-dimensional brain space.

We will also continue to enhance the scalability and performance of our core connectomics infrastructure, such as TensorStore for storage and Neuroglancer for visualization, in order to enable all of our computational pipelines and human analysis workflows to operate at these new scales of data. We’re eager to get to work to discover what peering into a mouse’s mind might tell us about our own.

Acknowledgements

The mouse connectomics project described in this blog post will be supported in part by the NIH BRAIN Initiative under award number 1UM1NS132250. Google Research is contributing computational and analytical resources to the mouse connectome project, and will not receive funding from the NIH. Many people were involved in the development of the technologies that make this project possible. We thank our long-term academic collaborators in the Lichtman Lab (Harvard University), HHMI Janelia, and the Denk Lab (Max Planck Institute for Biological Intelligence), and acknowledge core contributions from the Connectomics Team at Google. We also thank John Guilyard for creating the illustrative animation in this post, and Elise Kleeman, and Erika Check Hayden for their support. Thanks to Lizzie Dorfman, Michael Brenner, Jay Yagnik and Jeff Dean for their support, coordination and leadership.

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Last week at the inaugural Africa Climate Summit (ACS) in Nairobi, Kenya, we joined African leaders and shared our commitment to advance AI solutions to address the clim…Read More