Unlike the previous, 1-D versions of this light-emitting device, the new tool delivers light to the brain in three dimensions, opening the potential to explore entire circuits within the brain. So far, the 3-D version has been tested in mice, although Boyden and colleagues have used earlier optogenetic technologies with non-human primates as well.
Targeting neurons with light
One of the advantages of optogenetics is that this technology allows scientists to focus on one particular type of neuron without affecting other types of neurons in the same area of cortex. Probes that deliver electricity to the brain can manipulate neurons, but they cannot target individual kinds of cell, Boyden says. Drugs can turn neurons on or off as well, he continues, but not on such a quick time scale or with such a high degree of control. In contrast, the new 3-D array is precise enough to activate a single kind of neuron, at a precise location, with a single beam of light.
In an earlier incarnation, Boyden's device looked like a needle-thin probe with light-emitting ports along its length; this setup allowed scientists to manipulate neurons along a single line. The new tool contains up to a hundred of these probes in a square grid, which makes the device look like a series of fine-toothed combs laid next to each other with their teeth pointing in the same direction.
Each probe is just 150 microns across a little thicker than a human hair, and thin enough so that the device can be implanted at any depth in the cortex without damaging it. The brain lacks pain receptors, so the implants do not cause any discomfort to the brain itself. As in the earlier model, several light-emitting ports are located along the length of each probe. Scientists can illuminate and change the color of each light port independently from the others.
Adding a third dimension to the probe's light-delivery capabilities has allowed researchers to make any p
|Contact: Angela Stark|
Optical Society of America