Scientists say they’ve analyzed trillions of bytes’ worth of mapping data from the brain of a mouse to trace the connections within a tangle of neurons that’s smaller than a pinhead.
The results, published today in the journal Nature, mark a preliminary step toward an even more ambitious neuron-mapping project called MICrONS.
“This is the culmination of a research program that began almost 10 years ago,” study co-author R. Clay Reid, senior investigator at the Allen Institute for Brain Science, said in a news release. “Brain networks are too large and complex to understand piecemeal, so we used high-throughput techniques to collect huge data sets of brain activity and brain wiring.”
Reid and his colleagues identified neurons in the visual cortex of the mouse brain that responded to particular visual stimuli, such as the vertical or horizontal bars on a display screen. Then they sliced the brain into ultra-thin sections, took millions of ultra-detailed pictures of the neurons and rebuilt the sequence of pictures into a virtual 3-D view.
The view took in a section of brain tissue measuring no wider than 450 micrometers, which is less than half the width of a pinhead.
That was just the start: Teams of expert observers traced how 1,278 individual neurons branched out and connected with other neurons in the 3-D tangle.
The resulting maps supported the view that neurons with a similar function (for example, recognizing a pattern of vertical lines in a visual field) had stronger connections with each other, even though they were mixed up with other neurons that performed different functions.
Like MICrONS, the newly published work could lead to new insights into how individual neurons and the connections between them give rise to complex brain functions.
“It’s like a symphony orchestra with players sitting in random seats,” Reid explained. “If you listen to only a few nearby musicians, it won’t make sense. By listening to everyone, you will understand the music; it actually becomes simpler. If you then ask who each musician is listening to, you might even figure out how they make the music. There’s no conductor, so the orchestra needs to communicate.”
The data sets from the study are being made available online to other researchers.
Harvard Medical School’s Wei-Chung Allen Lee is the lead author of the Nature paper, titled “Anatomy and Function of an Excitatory Network in the Visual Cortex.” In addition to Lee and Reid, the authors include Vincent Bonin, Michael Reed, Brett Graham, Greg Hood and Katie Glattfelder.
