Here's a video of Harvard Medical School research published March 10 in Nature describing how scientists "crawled" through a mouse brain's cerebral cortex to map part of the neural circuitry that fired when they showed the mouse a movie.
From the Harvard press release:
Researchers in Harvard Medical School's Department of Neurobiology have developed a technique for unraveling these masses. Through a combination of microscopy platforms, researchers can crawl through the individual connections composing a neural network, much as Google crawls Web links.
"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 on a paper reporting the findings in the March 10 edition of Nature.
The cerebral cortex is arguably the most important part of the mammalian brain. It processes sensory input, reasoning and, some say, even free will. For the past century, researchers have understood the broad outline of cerebral cortex anatomy. In the past decade, imaging technologies have allowed us to see neurons at work within a cortical circuit, to watch the brain process information.
But while these platforms can show us what a circuit does, they don't show us how it operates.