neurodudes

How would you cure blindness, if your phototransducing rods and cones had degenerated - as happens in syndromes that affect millions of people worldwide? A lot of investigators have tried to create very complicated electrical stimulators that drive patterned activity in the retina. You need a power source, a camera of sorts, a computational element, and an array of electrodes that can crank out precise, well-timed current pulses, for a long time. It’s a heroic piece of optical and electrical engineering.

But what if you just made other cells in the retina light-sensitive? Channelrhodopsin and other light-activated ion channels have opened up this new kind of endeavor.

Investigators at Wayne State University, the Pennsylvania College of Optometry, and Beijing University have now done this. They expressed Channelrhodopsin in retinal ganglion cells (RGCs) of mice with photoreceptor degeneration. Remarkably, for months afterwards, the RGCs were able to transmit visual information all the way to visual cortex. In mice without channelrhodopsin, these visual evoked responses were never seen. A very impressive piece of systems bioengineering.

Ectopic Expression of a Microbial-Type Rhodopsin Restores Visual Responses in Mice with Photoreceptor Degeneration
Anding Bi, Jinjuan Cui, Yu-Ping Ma, Elena Olshevskaya, Mingliang Pu, Alexander M. Dizhoor, and Zhuo-Hua Pan

— Ed

This article in the latest issue of the Journal of Neuroscience is interesting in the sense that they are do human brain stimulation of the hypothalamus, for the treatment of cluster headaches - but they then do positron emission tomography (PET) to examine the downstream neural circuits responsible for the abolition of the perception of headache.

Hypothalamic Deep Brain Stimulation in Positron Emission Tomography

This moves the field of brain stimulation from simple stimulate-and-see-what-happens, towards more of a study of human neural circuitry and how stimulation drives activity in connected locations. It’s possible this will lead, in the future, to better and more focal stimulation protocols, as people figure out what the “circuit-level” phenomena are that correct particular aspects of neural dysfunction. Perhaps someday we will have a map of the “hot spots” where stimulation of a small chunk of matter can modulate a wide degree of neural circuitry for the better.

(Last year, Helen Mayberg and colleagues’ deep-brain-stimulation-and-depression paper got at this issue as well, in which they stimulate the cingulate and (perhaps surprisingly) sent depressed patients into remission, and furthermore changed the activity of frontal structures from the abnormal state, back to a more normal pattern of activity.)

These studies are perhaps setting a good precedent for brain-stimulating neuroclinicians to follow.

— Ed

Artificial limbs that walk naturally

Not too much info about the device, but basically, without any active electronics, the foot has a natural enough gait that people do not notice it is a prosthesis. Pretty cool.

This nytimes article points out that:

”
A top federal medical official overruled the unanimous opinion of his scientific staff when he decided last year to approve a pacemaker-like device to treat persistent depression, a Senate committee reported Thursday.

The device, the surgically implanted vagus nerve stimulator, had not proved effective against depression in its only clinical trial for treatment of that illness. As a result, scientists at the Food and Drug Administration repeatedly and unanimously recommended rejecting the application of its maker, Cyberonics Inc., to sell it as such a treatment, said the report, written by the staff of the Senate Finance Committee.

But Dr. Daniel G. Schultz, director of the Center for Devices and Radiological Health at the agency, kept moving the application along and eventually decided to approve it, the report said.

That approval did follow the backing of a divided F.D.A. advisory committee.

….

When some epilepsy patients reported that their moods had changed after receiving the devices, Cyberonics, based in Houston, implanted them in 235 depressed patients and turned the machines on in half of them. After three months, the two groups were equally depressed. The trial had failed.

Cyberonics then turned the devices on in all 235 patients and determined that 30 percent showed significant improvement after six months or more. Without a control group, however, it was impossible to determine if the device had caused the improvement.
“

This is from 9 months ago. It’s about a quadriplegic patient with a Cyberkinetics implant (100 electrode array) who can control a cursor decently. Here’s the link. Amazingly, Matthew says he learned to use the interface in only a couple of days (by which I infer he meant “start to basically use it”, not “have precise, skilled control of it”).

I have to point out that in my opinion, the article’s statement that “Neuroscientists can record and roughly translate the neural patterns of monkeys” is very misleading. It’s not that we can record ALL of the neural activity in a monkey, or completely translate all its thoughts; the best I’ve heard of is recording a tiny fraction related to motor planning and translating it into roughly which direction the monkey wants to move a limb.

His Holiness has spoken. He wants neuro-drugs to take and electrodes stuck in his brain so that he doesn’t have to spend hours meditating each day. (Enlightenment now!) If you want to do hot stuff, study physics or brain science. His interest in neuroscience stems from a long-standing interest in body hair. Yes, body hair. Americans need to figure their own way through this whole intelligent design business. Not all antidepressants are alike; for instance, the Dalai Lama is against tranquilizers. Definitely against tranquilizers. And, perhaps most surprisingly, His Holiness, approves of animal research — when it’s done right and with respect.

Minute-by-minute liveblog follows after the jump.
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This article is about efforts by six teams to develop a hippocampal prothesis by monitoring the input/output transformations performed by the hippocampus in slice, and then creating an electronic device to mimic them.

The article quotes noted memory researchers Howard Eichenbaum and Norbert Fortin who seem to approve of the methodology.

This review article (NRN Jan 2005) has a nice summary of cross-modal neuroplasticity in humans, mostly dealing with how occipital cortex (primarily visual for normals) takes over tactile and auditory processing duties in blind patients. The authors go on to speculate that these neuroplasticity insights could be applied to neural prothestic users to speed adaptation to their new sensory apparati, like combining tactile/auditory information with the prosthetic based stimulation. There’s also a nice comparison of visual implants at several levels, including retina, optic nerve, and cortex.

Cutting edge research groups.

Where in the world is the cutting edge in neural prosthetic design taking place?
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Neat article in today’s NYT on how a tongue stimulator can re-route many different sensory modalities. The most dramatic example (which the article focuses on) is how the device helps rehabilitate a patient with extensive vestibular damage and trains her brain to use whatever vestibular neurons she has left by this alternative (somatosensory) pathway. Click below for the full article.
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