Your brain is a complex organism, full of millions of different circuits and channels. These circuits are tangled, interconnected, and can be modified through a number of different chemicals, enzymes and other outside sources. They make your computer, and even the most technical pieces of equipment, seem like baby toys in comparison.
Harvard Medical School’s Department of Neurobiology team of researchers believe they have developed a technique for unraveling these complex circuits. Much like Google crawls web links, a combination of microscopy platforms allows researchers to crawl through the individual connections composing a neural network.
“The questions that such a technique enables us to address are too numerous even to list,” said Clay Reid, HMS professor of neurobiology and senior author of a paper reported in the March 10 edition of Nature.
In the anatomy of the brain, the cerebral cortex is said to be the most important part of the mammalian brain. It processes sensory input, reasoning and, some say, even free will. Researchers have understood the broad outline of cerebral cortex anatomy for the past century, but the past decade imaging technologies have allowed us watch the brain process information and to see neurons at work within a cortical circuit.
Reid’s lab has been studying the cerebral cortex for many years, modifying and adapting ways in which we can view the brain at work. They recently have been successful in isolating the activities of individual neurons and being able to watch them fire up in response to external stimuli. The ultimate prize, however, would be to get inside a single cortical circuit and probe the composition of its wiring, just one of these circuits, however, contains between 10,000 and 100,000 neurons, each of which makes about 10,000 interconnections, totaling upwards of 1 billion connections – all within a single circuit. “This is a radically hard problem to address,” Reid said.
The team began by studying the pint-sized region of a mouseâ€™s brain that involved processing of vision. The mouse was injected with dyes that flashed whenever specific neurons were fired and recorded the finding with a laser-scanning microscope. A large anatomy experiment was then conducted using electron microscopy to see the same neurons and hundreds of others with nanometer resolution.
Using a new imaging system they developed, the team recorded more than 3 million high-resolution images and sent them to the Pittsburgh Supercomputing Center at Carnegie Mellon University, where researchers stitched them into 3-D images. Using the resulting images, 10 individual neurons were painstakingly traced to create a partial wiring diagram.Â They found that neurons assigned to suppressing brain activity were seemingly randomly wired, suppressing local groups of neurons all at once rather than picking and choosing. These findings are important because many neurological conditions are the result of neural inhibition gone awry â€“ such as epilepsy.
“This is just the iceberg’s tip,” said Reid. “Within ten years I’m convinced we’ll be imaging the activity of thousands of neurons in a living brain. In a visual circuit, we’ll interpret the data to reconstruct what an animal actually sees. By that time, with the anatomical imaging, we’ll also know how it’s all wired together.”
“How the brain works is one of the greatest mysteries in nature,” Reid added, “and this research presents a new and powerful way for us to explore that mystery.”
Science Daily – Web-Crawling the Brain: 3-D Nanoscale Model of Neural Circuit Created:http://www.sciencedaily.com/releases/2011/03/110309131928.htm