A white laboratory mouse on a clean lab bench

Mus musculus · C57BL/6 · one of 139

A mouse with its own cortex.

621,733 recorded neurons from 139 mice, at their real positions. The most watched mouse this week has a human cortex. Ours is all mouse, and you can watch all of it.

▶Launch simulationreal mouse brain · live in-browser→ 1,908 neurons from one recorded mouse
play table tennis, ride a bike, walk a dog
Part-human, part-mouse brain developedBBC · Nature · 16 Sep 2026 →
SCROLL
621,733
Neurons recorded
139
Mice · 12 labs
279
Brain regions
699
Probe insertions

01 — The recording · live

Every dot is a recorded neuron.

The International Brain Laboratory recorded 621,733 neurons across the whole mouse brain while 139 mice did one decision task, and released every unit with its atlas position, region and firing rate. Below: all of them, on the Allen atlas, over a pale silhouette of 3.7 million mapped cells. Tint is firing rate. Pick a region to isolate it. Drag to turn.

The map was built to answer one question: how are the four parts of a decision, the stimulus, the choice, the feedback and the wheel movement, represented across the whole brain at once? The four populations that drive our tasks are those same four variables, found in one session by the same events.

REGION all
NEURONS —
MEDIAN RATE — Hz
low rate high rate atlas cell
DRAG · ROTATE

Positions and rates: IBL Brain-Wide Map aggregate table (2024 Q2), CC BY 4.0. Silhouette: Allen Brain Cell Atlas MERFISH cell coordinates, subsampled to 250,000. Rates are session means, not a live recording; the live spike replay is the next step, from the same public release.

02 — The story this week

Someone gave a mouse a human cortex.

A petri dish holding a small pale cluster of lab-grown brain tissue under a microscope, on a white bench

Sergiu Pașca's lab at Stanford, with St Andrews, grew human brain organoids from reprogrammed skin cells and implanted them into mice bred without a cortex. Over about six months the human cells wired into the mouse brain and fired with it. Published in Nature, reported by the BBC on 16 September 2026.

The mice then behaved like mice. No cognitive gain, the implanted cortex "a bit messy", the work limited to a few labs studying specific disorders, under independent ethical review.PARAPHRASED FROM THE BBC REPORT · NATURE s41586-026-11032-2

What this site does with it

Nothing, on purpose.

We do not have and do not use any data from that study. It is the reason people are looking at mouse brains this week; that is all. Everything here runs on two public releases with no login: the IBL Brain-Wide Map and the Allen Brain Cell Atlas.

  • No human cells, no organoids, no claim of cognition.
  • Every number traces to a row in a public file.
  • Limits stated before anyone asks.

03 — Two public releases

Where the dots come from.

A silicon electrode probe over a mouse at a wheel rig in a white lab
Recorded

IBL Brain-Wide Map

139 mice, 12 labs, 699 Neuropixels insertions, one standardised decision task. 621,733 units with Allen-atlas coordinates, 75,708 of them passing all quality checks. Aggregate table pulled from the public S3 bucket; spike trains per session are public too.

A thin mouse brain slice on a light table with tracer fibres glowing in one region
Mapped

Allen Brain Cell Atlas

Whole-brain MERFISH: about 3.7 million cells with atlas coordinates and cell-type labels. We use the coordinates only, as the pale silhouette the recorded neurons sit in.

The zebrafish from the ZEBRALINK site
Lineage

ZEBRALINK

This is the mouse sibling of our zebrafish site: same honesty rules, same split between what is recorded, what is fitted and what is engineered. The tasks now run on a model fitted to one mouse session.

04 — The tasks

What the mouse holds.

Drag · turn

The rider.

One white mouse, 6,000 triangles, built for the tasks. It was generated from a single side view, lifted to a shape by a local Hunyuan3D run, and textured by projecting that same view onto the mesh. It is a stand-in body, not an anatomical model; the brain above is the real part.

Triangles
6,000 · one draw call
File
mouse.glb · 0.8 MB
Made with
ChatGPT image → rembg → Hunyuan3D-2mini → Blender 5.1
DATA IBL BRAIN-WIDE MAP · CC BY 4.0
ATLAS ALLEN BRAIN CELL ATLAS
HOOK BBC · NATURE · 16 SEP 2026

05 — The scan

Where the wires go.

A tracer injected into primary visual cortex of one mouse lights up every axon it sends out. The Allen Institute imaged that whole brain at 100 µm; we track fibre paths on their density grid and draw them over the Allen average brain, coloured by direction the way a diffusion-MRI scan is: red left–right, green front–back, blue up–down.

Fibre paths from a visual-cortex tracer injection over a sagittal slice of the Allen average mouse brain
2,500 paths · Allen experiment 100141219 · VISp · wild typeOpen the scan →
DENSITY ALLEN MOUSE BRAIN CONNECTIVITY ATLAS
TEMPLATE ALLEN CCFv3 · 100 µm
TRACKING OURS · STRUCTURE TENSOR · DISCLOSED

06 — What the scientists are after

Five projects, one question.

Everything on this site sits on top of work by people trying to understand how a whole brain does a thing. Here is what each of them is actually trying to do, what we borrow, and what we do not claim.

A white mouse at a wheel rig with a screen and an electrode probe
International Brain Laboratory

Map a decision across a whole brain.

Their aim. Twelve labs recorded the same task the same way so that, for the first time in a mammal, a single decision could be followed neuron by neuron across every region. Their finding: the stimulus, the choice, the feedback and the wheel are represented far more widely than the classical areas; feedback shows up nearly everywhere.

What we do. Show all 621,733 of their neurons, then fit one session and let its four task variables drive a paddle, a bike and a leash.

Not claimed. That our model explains the decision. It predicts the next 62 ms of activity; that is all it is scored on.

A mouse brain slice with glowing tracer fibres
Allen Institute

Draw the wiring diagram.

Their aim. A mesoscale connectome of the mouse: thousands of tracer injections, each imaged through the whole brain and registered to one common atlas, so that every region's outputs can be looked up. And, separately, a cell-by-cell atlas of where each cell type sits.

What we do. Use their atlas as the silhouette behind the recordings, and track fibre paths on one of their visual-cortex injections for the scan.

Not claimed. That our paths are axons. They follow the density of the tracer; the tracing itself is theirs.

A petri dish of lab-grown brain tissue under a microscope
Stanford · Pașca lab

Put human cells in a living circuit.

Their aim. Psychiatry has one of the lowest success rates in clinical trials because mice do not get the human disorders. Human organoids grown into a mouse cortex are meant to be a model for those disorders: epilepsy, autism, cerebral palsy. The mice behaved as ordinary mice. No enhancement was found or sought.

What we do. Use the story as the reason to look closely at an all-mouse brain this week.

Not claimed. Anything about their data. We do not have it and do not model it.

A larval zebrafish in a light-sheet microscope
Google Research · Janelia

Predict a whole brain.

Their aim. A benchmark for forecasting cellular-resolution activity across an entire vertebrate brain (a larval zebrafish, 70,000 neurons), with the same brain being mapped at synapse level so that structure can later be added to the forecasts.

What we do. Our zebrafish site runs on that data; the mouse model here is the same kind of forecaster, scored the same way, on spikes instead of calcium.

Not claimed. Any result on their benchmark. Our fits are one-step, in the browser, for a task.

A fruit fly on the roof of a toy car on a white bench
The Driving Fly · STONKFLY

Give a mapped brain something to do.

Their aim. Take a brain that has been mapped or recorded, run it in a loop with a task (a car, a market), and be honest about the adapters between the two. The fly's connectome drives a car; STONKFLY wired a full retained fly simulation to guarded trading actions.

What we do. The same loop for a mouse, with disclosed adapters and no scripted outcomes.

Not claimed. That the mouse learns the task. The learning rule is on; the score says what happened.

A white mouse on a desk looking at a monitor full of blue dots
This site

The third kind of model.

A neuroscientist quoted in the story listed what her field has to work with: "mice, cells that live on a plate, and neural networks on a computer". This site is the third kind, fitted to the first. It adds nothing to the biology; it lets you watch a real recording drive something, with every step on the page.

Not claimed. Cognition, a disease model, or a brain that thinks. A mouse with its own cortex, and a computer keeping up with it.

07 — The subject

One mouse, on the record.

Everything the tasks run on comes from a single session in the IBL release. This is that session, as the public tables describe it, with nothing added.

Session

Subject
ZM_1897 · C57BL/6J
Lab
Mainen lab (Champalimaud Foundation)
Date
2019-12-02 · session 1
Protocol
_iblrig_tasks_ephysChoiceWorld6.1.3
Project
ibl_neuropixel_brainwide_01
Trials
413 · 354 correct · 59 errors · 85.7% accuracy
Contrasts
0%, 6.25%, 12.5%, 25%, 100%
Stimulus side
167 left · 192 right · rest zero contrast
Reward
1.5 µl water on a correct turn · white-noise burst on an error
Duration
41.5 minutes
Session id
dd4da095-4a99-4bf3-9727-f735077dba66

Probes

Probe 00
1,860 sorted units · 395 pass all checks
Isocortex 1,184 · OLF 676
Probe 01
865 sorted units · 141 pass all checks
HPF 373 · TH 330 · Isocortex 138
Sorting
pykilosort, IBL revision 2024-05-06
Used by us
1,908 units firing at 0.5 Hz or more, all labels
Model cells
545: 256 visual · 128 left · 128 right · 16 gate · 15 reward · 2 aversive

The task

IBL ChoiceWorld. After a short still period a grating appears 35° left or right; the mouse turns a wheel to bring it to the centre. A 1 mm turn moves it 4°. Correct: water. Wrong or too slow: a 500 ms noise burst. After 90 balanced trials the side is biased 80:20 in blocks. Described in the IBL paper's methods; we paraphrase.

One trial, in time, measured from this session. The line is the mean z-scored rate of our 256 visual cells around stimulus onset, 10 ms bins, 407 trials. The dashed marks are the session's own medians: the mouse's first wheel movement, the feedback, and the peak of the 15 reward cells after it. These are the numbers the model was fitted to, stated so the timing on the tasks page can be judged against them.

stimulus on · 0 msvisual cells peak · 180 msfirst wheel move (median) · 183 msfeedback (median) · 382 msreward cells peak · 602 ms-30002505007501000ms after stimulus onset0.54σ-0.11σ

08 — The ledger

What is recorded, what is fitted, what is made.

Every element on the site, sorted by how it came to be. Recorded means someone measured it in a mouse. Fitted means we computed it from a recording. Engineered means we built it. Generated means an image model drew it.

ElementStatusSourceWhere on the site
621,733 neuron positions, regions, firing ratesrecordedIBL Brain-Wide Map aggregate table, 2024 Q2Home · the map
3.7 million cell silhouetterecordedAllen Brain Cell Atlas MERFISH coordinatesHome · the map; tasks · brain panel
Spike times of 1,908 units, 42 minutesrecordedIBL session ZM_1897, public bucketFitted into the model
Trial events: stimulus, wheel, feedbackrecordedIBL trials table and wheel filesPopulation choice; the timeline above
Model weights (545 cells, 3 steps of history)fittedRidge regression on the spikes aboveTasks · every step at 16 Hz
Which cells see, steer, gate, receive rewardfittedRanked by response to the recorded eventsTasks · brain panel colours
Screen position of each visual cellfitted · adapterRank of stimulus-side preference and depthTasks · what the mouse sees
Gate threshold, steering scale, receptive fieldsengineered · adapterCalibrated to the recording's own statistics, disclosed in the footerTasks
Table, bike, street, park, dog, physicsengineeredThree.js scenes, 240 Hz physicsTasks
The white mouse ridergeneratedChatGPT side view → Hunyuan3D → BlenderHome · tasks
Tracer density of one injectionrecordedAllen Connectivity Atlas, experiment 100141219Scan
3,563 fibre pathsfittedGeodesic tracking on that density, oursScan
Average brain at 25 µm, region outlines and namesrecordedAllen CCFv3 template and 2017 annotationScan · slices and cursor readout
Photographs of benches, probes, dishes, animalsgeneratedImage model, styled after the equipment namedHome · card images
The Stanford chimera dataabsentNot held, not modelledNowhere, on purpose

09 — Foundations and downloads

The files, exactly.

Each public file the site is built from, with its licence, and the files we derived from them, so anyone can check a number.

CC BY 4.0 · International Brain Laboratory

Brain-Wide Map aggregate tables

Every unit with atlas coordinates, region, firing rate and quality label; every trial with its events.

…/aggregates/2024_Q2_IBL_et_al_BWM/clusters.pqt…/aggregates/2024_Q2_IBL_et_al_BWM/trials.pqt
CC BY 4.0 · International Brain Laboratory

Session ZM_1897 spike trains

Spike times and cluster ids for both probes, wheel position and timestamps, from the same public bucket.

…/data/mainenlab/Subjects/ZM_1897/2019-12-02/001/alf/
Allen Institute terms of use

Allen Brain Cell Atlas

MERFISH cell coordinates in the common coordinate framework, the silhouette behind the recordings.

alleninstitute.github.io/abc_atlas_access
Allen Institute terms of use

Mouse Brain Connectivity Atlas

Projection density of experiment 100141219 at 100 µm, plus the CCFv3 average template and 2017 annotation at 25 µm.

connectivity.brain-map.org/projection/experiment/100141219download.alleninstitute.org/…/mouse_ccf/
Ours · derived

The fitted model and the map data

What the pages load. Float16 weights, population ranges, held-out score, session facts, the packed positions.

data/model.jsondata/model.bindata/session.jsondata/meta.jsondata/scan/meta.json
MIT · lineage and papers

Code we build on, papers we cite

The execution and learning-rule lineage, the renderer, and the two papers behind the data.

github.com/nftechie/stonkflythreejs.org (MIT)IBL, Nature 2025Oh et al., Nature 2014