A wiring diagram for the brain
Synapse by synapse, researchers are mapping the brains of different species. The first data on the mouse brain already exist. But there is still a lot to be done before the complete circuit diagram of the human mind is available.
In April 2019, the atmosphere at the Allen Institute for Brain Science in Seattle (USA) was relaxed. In a room cluttered with five transmission electron microscopes, three shiny party balloons are flying around. Because the scientists are celebrating the latest success of an ambitious project: In a cubic millimeter of mouse brain – about the size of a grain of sand – they want to map each of the 100,000 neurons together with a billion connecting synapses.
For five months, the microscopes provided more than 100 million cross-sectional images of the mouse's visual cortex, each just 40 nanometers thick. From this, a program developed by the institute's computer specialists created a single 3D file within three months. The blue and silver lettering "2PB" emblazoned on the balloons stands for the size of the data set of two petabytes, i.e. two million gigabytes. For comparison, the Landsat mission had collected just 1.3 petabytes of satellite data from Earth in over 30 years. Thus, the mouse brain became a "world in a grain of sand," as Clay Reid, one of the Allen Institute's neurobiologists, remarked, in reference to the English poet William Blake.
The project represents just one of the attempts to create a nanoscale connectome for different species: a circuit diagram of the nervous system with synapse-precise resolution…