New array measures vibrations across the skin, may help engineers design optimal, wearable tactile displays.
In the near future, a buzz in your belt or a pulse from your jacket may give you instructions on how to navigate your surroundings.
Think of it as tactile Morse code: vibrations from a wearable, GPS-linked device that tell you to turn right or left, or stop, depending on the pattern of pulses you feel. Such a device could free drivers from having to look at maps, and could also serve as a tactile guide for the visually and hearing impaired.
Lynette Jones, a senior research scientist in MIT’s Department of Mechanical Engineering, designs wearable tactile displays. Through her work, she’s observed that the skin is a sensitive — though largely untapped — medium for communication.
“If you compare the skin to the retina, you have about the same number of sensory receptors, you just have them over almost two square meters of space, unlike the eye where it’s all concentrated in an extremely small area,” Jones says. “The skin is generally as useful as a very acute area. It’s just that you need to disperse the information that you’re presenting.”
Knowing just how to disperse tactile information across the skin is tricky. For instance, people may be much more sensitive to stimuli on areas like the hand, as opposed to the forearm, and may respond best to certain patterns of vibrations. Such information on skin responsiveness could help designers determine the best configuration of motors in a display, given where on the skin a device would be worn.
Now Jones has built an array that precisely tracks a motor’s vibrations through skin in three dimensions. The array consists of eight miniature accelerometers and a single pancake motor — a type of vibrating motor used in cellphones. She used the array to measure motor vibrations in three locations: the palm of the hand, the forearm and the thigh. From her studies with eight healthy participants, Jones found that a motor’s mechanical vibrations through skin drop off quickly in all three locations, within 8 millimeters from where the vibrations originated.
Jones also gauged participants’ perception of vibrations, fitting them with a 3-by-3 array of pancake motors in these three locations on the body. While skin generally stopped vibrating 8 millimeters from the source, most people continued to perceive the vibrations as far away as 24 millimeters.
When participants were asked to identify specific locations of motors within the array, they were much more sensitive on the palm than on the forearm or thigh. But in all three locations, people were better at picking out vibrations in the four corners of the array, versus the inner motors, leading Jones to posit that perhaps people use the edges of their limbs to localize vibrations and other stimuli.
“For a lot of sensory modalities, you have to work out what it is people can process, as one of the dictates for how you design,” says Jones, whose results will appear in the journal IEEE Transactions on Haptics. “There’s no point in making things much more compact, which may be a desirable feature from an engineering point of view, but from a human-use point of view, doesn’t make a difference.”
Mapping good vibrations
In addition to measuring skin’s sensitivity to vibrations, Jones and co-author Katherine Sofia ’12 found that skin has a strong effect on motor vibrations. The researchers compared a pancake motor’s frequency of vibrations when mounted on a rigid structure or on more compliant skin. They found that in general, skin reduced a motor’s vibrations by 28 percent, with the forearm and thigh having a slightly stronger dampening effect than the palm of the hand.
The skin’s damping of motor vibrations is significant, Jones says, if engineers plan to build tactile displays that incorporate different frequencies of vibrations. For instance, the difference between two motors — one slightly faster than the other — may be indistinguishable in certain parts of the skin. Likewise, two motors spaced a certain distance apart may be differentiable in one area but not another.
“Should I have eight motors, or is four enough that 90 percent of the time, I’ll know that when this one’s on, it’s this one and not that one?” Jones says. “We’re answering those sorts of questions in the context of what information you want to present using a device.”
Roberta Klatzky, a professor of psychology at Carnegie Mellon University, says that measurements taken by Jones’ arrays can be used to set up displays in which the location of a stimulus — for example, a pattern to convey a letter — is important.
“A major challenge is to enable people to tell the difference between patterns applied to the skin as, for example, blind people do when reading Braille,” says Klatzky, who specializes in the study of spatial cognition. “Lynette’s work sets up a methodology and potential guidelines for effective pattern displays.”
Creating a buzz
Jones sees promising applications for wearable tactile displays. In addition to helping drivers navigate, she says tactile stimuli may direct firefighters through burning buildings, or emergency workers through disaster sites. In more mundane scenarios, she says tactile displays may help joggers traverse an unfamiliar city, taking directions from a buzzing wristband, instead of having to look at a smartphone.
Using data from their mechanical and perceptual experiments, Jones’ group is designing arrays that can be worn across the back and around the wrist, and is investigating various ways to present vibrations. For example, a row of vibrations activated sequentially from left to right may tell a driver to turn right; a single motor that buzzes with increasing frequency may be a warning to slow down.
“There’s a lot of things you can do with these displays that are fairly intuitive in terms of how people respond,” Jones says, “which is important because no one’s going to spend hours and hours in any application, learning what a signal means.”
(Source: web.mit.edu)
![Memory-Boosting Chemical Is Identified in Mice
Memory improved in mice injected with a small, drug-like molecule discovered by UCSF San Francisco researchers studying how cells respond to biological stress.
The same biochemical pathway the molecule acts on might one day be targeted in humans to improve memory, according to the senior author of the study, Peter Walter, PhD, UCSF professor of biochemistry and biophysics and a Howard Hughes Investigator.
The discovery of the molecule and the results of the subsequent memory tests in mice were published in eLife, an online scientific open-access journal, on May 28, 2013.
In one memory test included in the study, normal mice were able to relocate a submerged platform about three times faster after receiving injections of the potent chemical than mice that received sham injections.
The mice that received the chemical also better remembered cues associated with unpleasant stimuli – the sort of fear conditioning that could help a mouse avoid being preyed upon.
Notably, the findings suggest that despite what would seem to be the importance of having the best biochemical mechanisms to maximize the power of memory, evolution does not seem to have provided them, Walter said.
“It appears that the process of evolution has not optimized memory consolidation; otherwise I don’t think we could have improved upon it the way we did in our study with normal, healthy mice,” Walter said.
The memory-boosting chemical was singled out from among 100,000 chemicals screened at the Small Molecule Discovery Center at UCSF for their potential to perturb a protective biochemical pathway within cells that is activated when cells are unable to keep up with the need to fold proteins into their working forms.
However, UCSF postdoctoral fellow Carmela Sidrauski, PhD, discovered that the chemical acts within the cell beyond the biochemical pathway that activates this unfolded protein response, to more broadly impact what’s known as the integrated stress response. In this response, several biochemical pathways converge on a single molecular lynchpin, a protein called eIF2 alpha.
Scientists have known that in organisms ranging in complexity from yeast to humans different kinds of cellular stress — a backlog of unfolded proteins, DNA-damaging UV light, a shortage of the amino acid building blocks needed to make protein, viral infection, iron deficiency — trigger different enzymes to act downstream to switch off eIF2 alpha.
“Among other things, the inactivation of eIF2 alpha is a brake on memory consolidation,” Walter said, perhaps an evolutionary consequence of a cell or organism becoming better able to adapt in other ways.
Turning off eIF2 alpha dials down production of most proteins, some of which may be needed for memory formation, Walter said. But eIF2 alpha inactivation also ramps up production of a few key proteins that help cells cope with stress.
Study co-author Nahum Sonenberg, PhD, of McGill University previously linked memory and eIF2 alpha in genetic studies of mice, and his lab group also conducted the memory tests for the current study.
The chemical identified by the UCSF researchers is called ISRIB, which stands for integrated stress response inhibitor. ISRIB counters the effects of eIF2 alpha inactivation inside cells, the researchers found.
“ISRIB shows good pharmacokinetic properties [how a drug is absorbed, distributed and eliminated], readily crosses the blood-brain barrier, and exhibits no overt toxicity in mice, which makes it very useful for studies in mice,” Walter said. These properties also indicate that ISRIB might serve as a good starting point for human drug development, according to Walter.
Walter said he is looking for scientists to collaborate with in new studies of cognition and memory in mouse models of neurodegenerative diseases and aging, using ISRIB or related molecules.
In addition, chemicals such as ISRIB could play a role in fighting cancers, which take advantage of stress responses to fuel their own growth, Walter said. Walter already is exploring ways to manipulate the unfolded protein response to inhibit tumor growth, based on his earlier discoveries.
At a more basic level, Walter said, he and other scientists can now use ISRIB to learn more about the role of the unfolded protein response and the integrated stress response in disease and normal physiology.](http://41.media.tumblr.com/11ebbfd04cfa4f78a2b3f00de596c905/tumblr_mofkpwCqOn1rog5d1o1_500.jpg)