First the scientist removes your scalp. Then your skull is cleared of connective tissue before men and women in the white coats set you on a treadmill and Krazy-Glue a metal bar to your skull. You're awake during all of this—and, if the surgery causes infection, you'll be euthanized.
Thankfully, if you're reading this, you're not a mouse—meaning you're safe from the very literal cutting edge of systems neuroscience. The new procedure, performed last month at New York City's Rockefeller University, allows researchers a rare, three-dimensional look into how a mammalian brain works in real time, tracking the effects of a mouse's every thought and action within the brain.
Known as "fast volumetric calcium imaging," the light sculpting technique allows for a rare glimpse into how the brain's neurons interact with one another. "[We use] it to capture the activity of the majority of the neurons within a large portion of the cortex—a layered brain structure involved in higher brain function," said lead researcher Alipasha Vaziri in a press release issued by Rockefeller University.
To achieve the effect, researchers use a special laser that pulsates ultra-quick—to the quadrillionth of a second—laser light through neurons in the cortex. Each pulse captures a single two-dimensional image. Because the light pulsates so quickly, however, the researchers are able to stitch the images together to create a real-time, three-dimensional replication of the working brain.
Vaziri and his team began the process six years ago when they first analyzed the 302-neuron brain of a roundworm. Then they studied the 100,000-neuron larval zebrafish brain, and now a mouse brain, which contains about 70 million neurons.
Making things more difficult, mammalian brains are made of squishy gray matter, as opposed to the mostly transparent—and therefore easier to image—worm and fish brains that Vaziri's team had previously studied.
Cats (760 million neurons) could be next mammals to be studied, likely followed by squirrel monkeys (3.4 billion neurons). The average human brain contains about 86 billion neurons, which means researchers still have to make their way further up the mammalian food chain before playing Operation on your dome.