The U.S. Women’s Team Win Gold At The 2014 Nanning World Championships

May 18, 1969 — Inside mission control at the Johnson Space Center, Houston, during the first day of the Apollo 10 mission. (NASA)

Spinal Stimulators Repurposed to Restore Touch in Lost Limb

Imagine tying your shoes or taking a sip of coffee or cracking an egg but without any feeling in your hand. That’s life for users of even the most advanced prosthetic arms.

Although it’s possible to simulate touch by stimulating the remaining nerves in the stump after an amputation, such a surgery is highly complex and individualized. But according to a new study from the University of Pittsburgh’s Rehab Neural Engineering Labs, spinal cord stimulators commonly used to relieve chronic pain could provide a straightforward and universal method for adding sensory feedback to a prosthetic arm.

For this study, published in eLife, four amputees received spinal stimulators, which, when turned on, create the illusion of sensations in the missing arm.

“What’s unique about this work is that we’re using devices that are already implanted in 50,000 people a year for pain — physicians in every major medical center across the country know how to do these surgical procedures — and we get similar results to highly specialized devices and procedures,” said study senior author Lee Fisher, Ph.D., assistant professor of physical medicine and rehabilitation, University of Pittsburgh School of Medicine. 

The strings of implanted spinal electrodes, which Fisher describes as about the size and shape of “fat spaghetti noodles,” run along the spinal cord, where they sit slightly to one side, atop the same nerve roots that would normally transmit sensations from the arm. Since it’s a spinal cord implant, even a person with a shoulder-level amputation can use this device 

Fisher’s team sent electrical pulses through different spots in the implanted electrodes, one at a time, while participants used a tablet to report what they were feeling and where.

All the participants experienced sensations somewhere on their missing arm or hand, and they indicated the extent of the area affected by drawing on a blank human form. Three participants reported feelings localized to a single finger or part of the palm.

“I was pretty surprised at how small the area of these sensations were that people were reporting,” Fisher said. “That’s important because we want to generate sensations only where the prosthetic limb is making contact with objects.”

When asked to describe not just where but how the stimulation felt, all four participants reported feeling natural sensations, such as touch and pressure, though these feelings often were mixed with decidedly artificial sensations, such as tingling, buzzing or prickling.

Although some degree of electrode migration is inevitable in the first few days after the leads are implanted, Fisher’s team found that the electrodes, and the sensations they generated, mostly stayed put across the month-long duration of the experiment. That’s important for the ultimate goal of creating a prosthetic arm that provides sensory feedback to the user. 

“Stability of these devices is really critical,” Fisher said. “If the electrodes are moving around, that’s going to change what a person feels when we stimulate.” 

The next big challenges are to design spinal stimulators that can be fully implanted rather than connecting to a stimulator outside the body and to demonstrate that the sensory feedback can help to improve the control of a prosthetic hand during functional tasks like tying shoes or holding an egg without accidentally crushing it. Shrinking the size of the contacts — the parts of the electrode where current comes out — is another priority. That might allow users to experience even more localized sensations. 

“Our goal here wasn’t to develop the final device that someone would use permanently,” Fisher said. “Mostly we wanted to demonstrate the possibility that something like this could work.”

Sleeping brain's complex activity mimicked by simple model

Researchers have built and tested a new mathematical model that successfully reproduces complex brain activity during deep sleep, according to a study published in PLOS Computational Biology.

Recent research has shown that certain patterns of neuronal activity during deep sleep may play an important role in memory consolidation. Michael Schellenberger Costa and Arne Weigenand of the University of Lübeck, Germany, and colleagues set out to build a computational model that could accurately mimic these patterns.

The researchers had previously modeled the activity of the sleeping cortex, the brain’s outer layer. However, sleep patterns thought to aid memory arise from interactions between the cortex and the thalamus, a central brain structure. The new model incorporates this thalamocortical coupling, enabling it to successfully mimic memory-related sleep patterns.

Using data from a human sleep study, the researchers confirmed that their new model accurately reproduces brain activity measured by electroencephalography (EEG) during the second and third stages of non-rapid eye movement (NREM) sleep. It also successfully predicts the EEG effects of stimulation techniques known to enhance memory consolidation during sleep.

The new model is a neural mass model, meaning that it approximates and scales up the behavior of a small group of neurons in order to describe a large number of neurons. Compared with other sleep models, many of which are based on the activity of individual neurons, this new model is relatively simple and could aid in future studies of memory consolidation.

“It is fascinating to see that a model incorporating only a few key mechanisms is sufficient to reproduce the complex brain rhythms observed during sleep,” say senior authors Thomas Martinetz and Jens Christian Claussen.

Sainte-Geneviève Library. Paris, France.  

Green method developed for making artificial spider silk

A team of architects and chemists from the University of Cambridge has designed super-stretchy and strong fibres which are almost entirely composed of water, and could be used to make textiles, sensors and other materials. The fibres, which resemble miniature bungee cords as they can absorb large amounts of energy, are sustainable, non-toxic and can be made at room temperature.

This new method not only improves upon earlier methods of making synthetic spider silk, since it does not require high energy procedures or extensive use of harmful solvents, but it could substantially improve methods of making synthetic fibres of all kinds, since other types of synthetic fibres also rely on high-energy, toxic methods. The results are reported in the journal Proceedings of the National Academy of Sciences.

Spider silk is one of nature’s strongest materials, and scientists have been attempting to mimic its properties for a range of applications, with varying degrees of success. “We have yet to fully recreate the elegance with which spiders spin silk,” said co-author Dr Darshil Shah from Cambridge’s Department of Architecture.

Read more.

Mesquite Dunes | California (by Chris Lazzery)

Irving Langmuir, who won the 1932 Nobel Prize for ‘Surface Chemistry’, demonstrates how dipping an oil-covered finger into water creates a film of oil, pushing floating particles of powder to the edge.

The same phenomenon can be used to power a paper boat with a little ‘fuel’ applied to the back: as the film expands over the water, the boat is is propelled forward:

With experiments like this he revealed that these films are just one molecule thick - a remarkable finding in relation to the size of molecules.

In the full archive film, Langmiur goes on to demonstrate proteins spreading in the same way, revealing the importance of molecular layering for structure.

First, he drops protein solution onto the surface, and it spreads out in a clear circle, with a jagged edge: 

Add a little more oil on top, and a star shape appears: 

By breaking it up further, he makes chunks of the film which behave like icebergs on water:

You can watch the full demonstrations, along with hours more classic science footage, in our archive.

Packing numerous books and papers that he plans to read over winter break, the grad student deludes himself.

Building microfluidic circuits is generally a multi-day process, requiring a clean room and specialized manufacturing equipment. A new study suggests a quicker alternative using fluid walls to define the circuit instead of solid ones. The authors refer to their technique as “Freestyle Fluidics”. As seen above, the shape of the circuit is printed in the operating fluid, then covered by a layer of immiscible, transparent fluid. This outer layer help prevent evaporation. Underneath, the circuit holds its shape due to interfacial forces pinning it in place. Those same forces can be used to passively drive flow in the circuit, as shown in the lower animation, where fluid is pumped from one droplet to the other by pressure differences due to curvature. Changing the width of connecting channels can also direct flow in the circuits. This technique offers better biocompatibility than conventional microfluidic circuits, and the authors hope that this, along with simplified manufacturing, will help the technique spread. (Image and research credit: E. Walsh et al., source)