KBrain Map
Real brain maps, measured.
We read neuroscience from the actual connectome data (human, mouse and fly) and publish our numbers, our methods and our mistakes.
Maps →
The public brain maps we measure from: human cortex (H01), mouse (MICrONS) and fly (FlyWire). What they are and how to open them.
Numbers →
Every number we measured, with the map it came from, how we measured it and what it does not show.
Stories →
Write-ups of each measurement: cells and wiring, drugs and receptors, myths checked, methods and corrections.
Latest stories
What Fraction of Neurons Are Inhibitory in the Human Cortex? About 31% in Our Count (vs 12% in Mouse)
In about one cubic millimetre of human cortex (H01), 4,688 of 15,219 classified neurons are inhibitory interneurons: 31%. In a mouse cortex map (MICrONS) we count 12%. How we counted, how it changes by layer, and what the number does not tell you.
What Is in Layer 1 of the Human Cortex? Few Neurons, Many Astrocytes
In a cubic millimetre of human cortex (H01), only 18% of layer-1 cells are neurons (827 of 4,595), against 70% in layer 2. The most common cell is the astrocyte: 37%. What else is there, why the layer is mostly wiring, and the caveats.
Which Brain Cells Spread Out Evenly? Microglia and OPCs in Every Cortical Layer
In a cubic millimetre of human cortex (H01), microglia and OPCs sit at about 6,000 per mm³ in every layer, from 5,854 to 6,519 (a 1.1-fold range). Neurons vary 6.4-fold across the same layers. The numbers, one likely reason, and the caveats.
What Is the Most Common Cell in the Human Brain? In This Sample, Not the Neuron
In about one cubic millimetre of human cortex mapped with an electron microscope (H01), oligodendrocytes outnumber neurons 20,139 to 16,087. Half of them sit in the white matter. In the grey matter alone, neurons still win. Here is the count, layer by layer.
Why Is White Matter White? 31.5% of Its Mapped Volume Is Myelinated Axons
White matter looks white because it is packed with myelin, a fatty wrapping around nerve fibres. In a real human cortex sample (H01), myelinated axons fill 31.5% of the mapped white-matter volume but only 1.0% of layer 1. Raw electron-microscope images and the numbers.
Does Parkinson's Start Only After 80% of Neurons Die? We Traced the Number Back to Its Sources
A widely repeated line says 80% of dopamine neurons are already gone when Parkinson's symptoms appear. We read the studies behind it. For the cells themselves, the best estimate is closer to 30%; the 80% is about something else.
How Close Are Neurons to Blood Vessels? We Measured 10,441 of Them in a Real Human Brain Sample
In about one cubic millimetre of human cortex mapped with an electron microscope (H01), 98% of neurons sit within 50 µm of a blood vessel (median 23 µm). How we measured it, why neurons stay so close, and what the number does not tell you.
Is Dopamine the Pleasure Chemical? Not Quite. 390 Fly Neurons, One Receptor, and What the Experiments Say
We counted the predicted dopamine neurons in a complete fruit-fly connectome, looked at dopamine bound to the human D1 receptor, and checked the 'pleasure chemical' label against the monkey and rat experiments behind it. Includes the four things we fixed before publishing.