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Neuroprosthetics, Brain-Computer Interfaces, and Optogenetics

Your brain is composed of 100 billion cells called neurons.

These cells make you who you are and control everything you do, think and feel.

In combination with your sensory organs (i.e., eyes, ears), these systems shape how you perceive the world.

And sometimes, they can fail.

That's where neuroprosthetics come into the picture.

The term "neuroprosthetics" describes the use of electronic devices to replace the function of impaired nervous systems or sensory organs.

They've been around for a while ? the first cochlear implant was implanted in 1957 to help deaf individuals hear ? and since then, over 350,000 have been implanted around the world, restoring hearing and dramatically improving quality of life for those individuals.

But such a cochlear implant only hints at a very exciting field that researchers call the brain-computer interface, or BCI: the direct communication pathway between the brain (central nervous system, or CNS) and an external computing device.

The vision for BCI involves interfacing the digital world with the CNS for the purpose of augmenting or repairing human cognition.

And how we interface with the CNS is where it becomes interesting.

There are two approaches. The first is physically connecting wires and neurons with microscopic arrays of metallic pins that stick into the brain and electrically stimulate neurons and/or measure the neuron's electric potential when they fire.

The second, and far more interesting, approach is the arena of "optogenetics" ? controlling neurons with light. Using this mechanism, a light-sensitive molecule is inserted into the cell surface of a neuron (usually through a virus vector). The light-sensitive molecule can then allow an outside user to trigger or inhibit the neuron's firing by pulsing a specific frequency of light.

The entire BCI and neuroprosthetics field is just at its infancy today.

To get you thinking about the possibilities, here are a few of my favorite applications illustrating what we can do today.

Today's Applications

1. Seeing: About 70 blind people have undergone the 3-hour surgery for what’s called a “retinal implant.” As described, “a spectacle-mounted camera captures image data; that data is then processed by a mini-computer carried on a strap and sent to a neuron-stimulating array of 60 electrodes implanted on the retina.” While still a long way from completely restoring vision, the notion that we can use cameras to augment or replace lost photoreceptors is promising.

2. Hearing: As I mentioned earlier, around 350,000 cochlear implants have been implanted in hard-of-hearing individuals over the last 60 years. A microphone picks up sound from the environment, sends it to a speech processor, and then a transmitter converts it into electric impulses. An electrode array sends these impulses to different regions of the auditory nerve, allowing us to bypass the malfunctioning parts of the ear all together.

3. Feeling Pain: Various companies and research groups (including Stanford University) are exploring how to use optogenetics to “turn off” the perception of chronic pain simply by pressing a bright flashlight to a patient’s skin. Pain is the primary reason people see doctors, accounting for $635 billion per year.

4. Movement/Intention: Fifteen to 20 paralyzed patients have received implants into the motor cortex (the area of the brain that controls movement) that allow them to control external robotic arms or, even more amazingly, reanimate paralyzed limbs by stimulating electrodes implanted in the limb.

5. Hunger: Like pain, hunger is a sensation. Stanford researchers are exploring how to use

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