Wednesday, May 7, 2014

Computer Game Reveals 'Space-Time' Neurons in the Eye

Motion detector. The key insight from a mapping of neurons in the retina is that these inner (purple) cells fire more slowly than the outer (pink) cells, and this arrangement causes the big branching cells (yellow) to fire only when light arrives from obj 
Motion detector. The key insight from a mapping of neurons in the retina is that these inner (purple) cells fire more slowly than the outer (pink) cells, and this arrangement causes the big branching cells (yellow) to fire only when light arrives from objects moving in certain directions.

You open the overstuffed kitchen cabinet and a drinking glass tumbles out. With a ninjalike reflex, you snatch it before it shatters on the floor, as if the movement of the object were being tracked before the information even reached your brain. According to one idea of how the circuitry of the eye processes visual data, that is literally what happens. Now, a deep anatomical study of a mouse retina—carried out by 120,000 members of the public—is bringing scientists a step closer to confirming the hypothesis. 

Researchers have known for decades that the eye does much more than just detect light. The dense patch of neurons in the retina also processes basic features of a scene before sending the information to the brain. For example, in 1964, scientists showed that some neurons in the retina fire up only in response to motion. 

What's more, these “space-time” detectors have so-called direction selectivity, each one sensitive to objects moving in different directions. But exactly how that processing happens in the retina has remained a mystery.

The stumbling block is a lack of fine-grained anatomical detail about how the neurons in the retina are wired up to each other. Although researchers have imaged the retina microscopically in ultrathin sections, no computer algorithm has been able to accurately trace out the borders of all the neurons to map the circuitry. At this point, only humans have good enough spatial reasoning to figure out what is part of a branching cell and what is just background noise in the images.

Enter the EyeWire project, an online game that recruits volunteers to map out those cellular contours within a mouse’s retina. The game was created and launched in December 2012 by a team led by H. Sebastian Seung, a neuroscientist at the Massachusetts Institute of Technology in Cambridge. Players navigate their way through the retina one 4.5-micrometer tissue block at a time, coloring the branches of neurons along the way. Most of the effort gets done in massive online competitions between players vying to map out the most volume. (Watch a video of a player walking through a tissue block here.) By last week, the 120,000 EyeWire players had completed 2.3 million blocks. That may sound like a lot, but it is less than 2% of the retina.

For the rest of the story: http://news.sciencemag.org/brain-behavior/2014/05/computer-game-reveals-space-time-neurons-eye

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