Shown here is the visual reconstruction of synapses in part of the mouse cortex that responds to whisker stimulation. Neurons are depicted in green. Multicolored dots represent separate synapses— about one billion of them per cubic millimeter of tissue. Credit: Stephen Smith
The cortex of the human brain holds more than 100 trillion neural connections, or synapses, packed into a layer of tissue just 2 to 4 millimeters thick. Visualizing these densely packed units individually has proved extremely challenging. Synapses in the brain are crowded in so close together that they cannot be reliably resolved by even the best of traditional light microscopes.
Smith and collaborators have developed a new technology that highlights all the synapses in the mouse cortex. “Now we can actually count them and, in the bargain, catalog each of them according to its type,” he says. [source]
Henry Markram is director of Blue Brain, a supercomputing project that can model components of the mammalian brain to precise cellular detail — and simulate their activity in 3D. Soon he’ll simulate a whole rat brain in real time.
“If you zoom into the surface of neocortex, you discover that it’s made up of little modules [neocortical columns], G5 processors, like in a computer. But there are about million of them. They were so successful in evolution that what we did was to duplicate them over and over and add more and more of them to the brain…so that we’d have more neocortical columns to perform more complex functions.
So you can think of the neocortex actually as a million-key grand piano. Each of these neocortical columns would produce a note. You stimulate it; it produces a symphony. But it’s not just a symphony of perception. It’s a symphony of your universe, your reality.
So, the Holy Grail for neuroscience is really to understand the design of the neocortical column - and it’s not just for neuroscience; it’s perhaps to understand perception, to understand reality…”