26 January 2011

Beware the Spying Optical Needle: It Can See Your Thoughts

Dubbed the optical needle, it is 500 to 1,000 microns in diameter at its tip—about half the width of a grain of rice. While the device resembles a scaled-down version of the endoscopes now commonly used for surgery, the tiny lens is slightly different. The small size of the device means that a curved lens, typical in most microscopes, is impractical. Instead, its lens is made from a material that has internal variations in its refractive profile to guide rays of light.

...In the new study, published online this month in Nature Medicine, researchers demonstrate that they can use the micro-endoscope to observe the same spot in the brain over time. _TechnologyReview

Brain probes are becoming smaller and more clever. The "optical needle" is a micro-endoscopic probe from Stanford, which is capable of long-term direct observation of local brain circuits, deep inside the brain.
A new type of micro-endoscope lets scientists watch nerve cells and blood vessels deep inside the brain of a living animal over days, weeks, or even months. A team led by Mark Schnitzer, associate professor of biology and applied physics at Stanford University, developed the endoscope—an optical instrument used to peer into the body—along with a system to insert it into the same spot time after time. This feature allowed scientists to track changes in minute features, such as the connections between cells in the brain.

"I think it will be a potent tool for tracking properties of cells over long periods of time in response to changes in the environment, over the course of learning, during aging or the progression of disease," says Schnitzer. Some developmental and neurodegenerative diseases, for example, damage connections between neurons deep in the brain.

Of particular interest to neuroscientists is the hippocampus, an area deep in the brain that is crucial to memory. Previously, scientists had been able to look at regions such as this one in detail only with highly invasive methods and at a single point in time. "But a lot of brain disorders occur slowly," says Schnitzer. "We don't just want a snapshot, we want a time-lapse [movie] on a time scale that is relevant to the progression of the disease." _TechnologyReview
The researchers first insert a tiny indwelling guide tube, then pass the optical needle through the tube for optical micro-imaging. Since the tube remains in the same location, the researchers can come back time and again to image the same location -- providing an ongoing time-lapse record of changes in cellular structure at that spot. The tool should provide many opportunities for study, and eventual clinical application.

By placing guide tubes in strategic locations around a brain tumour, for example, clinicians might be able to monitor the effects of experimental treatments.

But what about seeing your thoughts? Be patient, grasshoppers. Current optical needle technology can observe changes in the micro-structure of local brain circuits. As the technology improves, distributed observers will be able to watch a brain learning with experience. Combined with sophisticated deep brain stimulation and advanced neurofeedback, a sufficiently motivated mad scientist could learn to play any human brain like a piccolo.

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