“The audacious science pushing the boundaries of human touch”<\/a><\/p>\nBy Cynthia Gorney,\u00a0<\/span>Photographs by Lynn Johnson, National Geogrpahic Magazine, June 2022 Issue<\/span><\/p>\nIt’s the first sensation we feel, our most primal connection to others. Can implants and electrical signaling replicate the experience of touch? Research teams are exploring the possibilities\u2014with startling results.<\/em><\/p>\nOne afternoon<\/b> in September 2018, six years after the work accident that destroyed his left forearm and hand in an industrial conveyor belt, a North Carolina man named Brandon Prestwood stood in front of his wife with an expression on his face that was so complicated, so suffused with nervous anticipation, that he looked torn between laughter and tears. In the little group gathered around the Prestwoods, someone held up a cell phone to record the curious tableau: the pretty woman with long hair and glasses, the bearded guy with a white elbow-to-fingertips prosthetic, and the wiring running from a tabletop electrical device up under the guy\u2019s shirt and into his shoulder.<\/p>\nRight through the skin, that is, so that Prestwood\u2014his body, not his prosthetic\u2014was, for the moment, literally plugged in. As part of an audacious set of experiments by an international network of neurologists, physicians, psychologists, and biomedical engineers, Prestwood had let surgeons at Cleveland\u2019s Case Western Reserve University slice into the end of his left arm and affix tiny electrical conductors to the truncated nerves and muscles. The surgeons then guided four dozen thread-thin wires up inside his half arm and out his shoulder. Afterward, whenever he peeled off the patch that covered them, Prestwood could see the wire leads poking out of his skin.Welp, yep, they\u2019re wires,<\/i> Prestwood would say to himself. Coming out of my arm.<\/i>He\u2019d wasted too much time lost in depression after the accident. He felt purposeful now. And for some months he\u2019d been making regular trips to Cleveland so that researchers could help him fasten on an experimental prosthetic arm, one of a new generation of artificial limbs with internal motors and sensor-equipped fingers. These devices are of great interest to rehab experts, but what the Case Western Reserve team most wanted to study was not simply the improved control the new prostheses provide. What really fascinated the researchers\u2014the focus of their exploration, each time they sat Prestwood down in the lab and plugged his wire leads into a computer\u2014was the experience of human touch.<\/p>\n\n
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PRIMAL DRIVE<\/span><\/p>\n\n
A famous and harrowing 1950s experiment demonstrated the profound need for touch comfort. Influential child experts of the era were admonishing parents not to cuddle their babies: Harmful overindulgence, they insisted. Wisconsin psychologist Harry Harlow helped prove how wrong they were. His team isolated baby monkeys in cages with two fake mother \u201csurrogates.\u201d Even though only this bare wire monkey gave milk, the babies usually spurned it, clinging to the soft touch of the surrogate wrapped in cloth.<\/span><\/span><\/div>\n<\/div>\nPHOTOGRAPH BY AL FENN, LIFE PICTURE COLLECTION\/SHUTTERSTOCK<\/span><\/p>\n<\/div>\n<\/div>\n<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/aside>\n<\/div>\n
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A BODY’S SIGNALS<\/span><\/p>\n\n
Arizona chiropractor John Ball treats world-class athletes\u2014his grimacing patient on the massage table is American middle-distance runner Ben Blankenship\u2014with powerful hands that manipulate while simultaneously picking up cues about muscle and bone. \u201cI know how to use tissue and tactile feedback from the person\u2019s body,\u201d Ball says. \u201cThe more tactile sense, the more skin receptors you can stimulate, the more information you\u2019re bouncing back and forth between the local environment and the brain.\u201d<\/span><\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/figcaption><\/figure>\n\n
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CLOSE CONTACT<\/span><\/p>\n\n
Inside New Delhi\u2019s Safdarjung Hospital, just born twins nestle against the skin of their aunt Neerja Kumari, while their mother, Sunita, recuperates. Kangaroo mother care\u2014attending to newborns while they rest skin-to-skin against the mother or a surrogate\u2014is well known, especially in developing countries, as a way to strengthen fragile low-birth-weight babies. A recent study coordinated by the World Health Organization at Safdarjung and four African hospitals found that kangaroo care is even more effective when it\u2019s nearly continuous and starts immediately after birth, rather than for a few hours a day after the baby is judged stable. Researchers estimate this approach could save 150,000 lives a year.<\/span><\/span><\/div>\n<\/div>\nPHOTOGRAPH BY SAUMYA KHANDELWAL<\/span><\/p>\n<\/div>\n<\/div>\n<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/aside>\n<\/div>\n
Because it\u2019s damnably, wondrously complicated, this critical interplay of skin, nerves, and brain: to understand, to measure, and to re-create in a way that feels \u2026 human. That\u2019s not a very scientific way to put it, but Brandon Prestwood is a case in point. Inside the Sensory Restoration Lab, as the Case Western Reserve researchers ran him through tests, there were encouraging developments; when Prestwood made the prosthetic hand close around a foam block, for example, he felt a pressure against the foam. A connection. A tingling that seemed to be coming from fingers he no longer possessed.<\/p>\n
Amy Prestwood had never been able to join her husband, though, during his lab sessions in Cleveland. It was not until that September afternoon, when she went to the Maryland research symposium where Brandon was among the demonstrators of new technology, that the two of them could stand within reaching distance while Brandon was wearing the experimental prosthesis with his shoulder wires plugged in.<\/p>\n
Brandon keeps on his phone that video recording of what happened next. He still loses his composure when he talks about it. No one has edited or polished this clip; all you see is two people facing each other in a big room, uncertain and awkward, like adolescents at a first dance. Brandon looks at his feet, looks at his prosthetic fingers, grins. With his right arm, the intact one, he points Amy toward his left: Come over here.<\/p>\n
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PATCH WORK<\/span><\/p>\n\n
Even the simplest touch to skin sets off neural messaging so complex that scientists are only beginning to mimic it through engineering. At the Johns Hopkins Applied Physics Laboratory, researchers are exploring an approach that uses what\u2019s known as e-dermis: pressure-reactive layered material. When attached to prosthetic hands, like the one holding this e-dermis patch, the material helps turn contact with another surface into a sensation the brain interprets as touch.<\/span><\/span><\/div>\n<\/div>\nPHOTOGRAPH BY MARK THIESSEN<\/span><\/p>\n<\/div>\n<\/div>\n<\/figcaption><\/figure>\n<\/div>\n<\/div>\n<\/aside>\n<\/div>\n
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The growing literature<\/b> about our sense of touch is rich with new science, conjecture, and fantastical propositions for the future\u2014but there are four seconds in that video I want to describe, just as Amy wraps her fingers around the hand of Brandon\u2019s prosthetic. His head snaps up. His eyes widen. His mouth falls open. She\u2019s watching him, but Brandon is staring straight out, plainly not seeing anything. \u201cI could feel,<\/i>\u201d he told me. \u201cI was getting feedback. I was touching her. I was crying. I think she was crying.\u201d<\/p>\n
She was. The day he showed me the video we were deep into the pandemic and sitting outdoors; Prestwood had been in the Cleveland lab for hours and wanted a cigarette. We\u2019d met in person for the first time that morning. I can\u2019t remember how we resolved the hesitant do-we-shake-hands-or-not moment\u2014hesitant not because Prestwood has only one hand, but because it seemed as though everybody on Earth was still trying to figure out how to approach each other, how fully to close the distance, how to touch.<\/p>\n
Maybe you recall the photos of people pandemic-embracing through shower curtains or hanging plastic. This magazine published an especially affecting one, a clear drop cloth clipped to a clothesline; with the plastic between them, a woman and her daughter clung to each other for the first time in months. I swear I know the sound and feel of that moment: My own daughter improvised something similar, after the weird aching season of across-the-backyard distanced visits, and I can still bring to mind the mercy of that hug.<\/p>\n
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NEW SENSATIONS<\/span><\/p>\n\n
When Brandon Prestwood\u2019s shoulder wires are connected to a computer stimulator, they carry signals to electrodes implanted in his upper arm. Combined with an experimental prosthesis, this can give Prestwood\u2014whose lower arm was amputated after an accident\u2014touch sensations that feel as though they\u2019re coming from that missing hand. At home in North Carolina, Prestwood uses alcohol swabs to clean around his wires. The tattoo honors one of the two infants he and his wife lost to amniotic fluid infections. His plea, as a research volunteer: Don\u2019t damage the tattoo.<\/span><\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/figcaption><\/figure>\n\n
Through a barrier, yes. Crinkly, slippery. Plasticky. A diminishment, you\u2019d think. But my \u201cneed state,\u201d as Liverpool John Moores University neuroscientist Francis McGlone puts it, was too heightened for me to notice. \u201cIt\u2019s like being low on a vitamin,\u201d McGlone told me. \u201cYou needed to be topped up again.\u201d<\/p>\n
Topped up with what, exactly? My grandmother would have looked at me sideways for imagining that was a question that merited answering. But neurologists and psychologists have biological markers now to explain what seems intuitively obvious to so many of us\u2014that most human beings require the physical presence of others, the comforting touch of others, in order to stay healthy. Take in this academic-sounding prose, before I tell you where it first appeared:<\/p>\n
Touch is a fundamental aspect of social interaction, which is a fundamental human need \u2026 Social touch calms the recipient of the touch during stressful experiences \u2026 can reduce activation in threat-related regions of the brain \u2026 can influence activation in the stress pathway in the nervous system, reducing levels of the stress hormones \u2026 has been found to stimulate the release of oxytocin, a neuropeptide produced in the hypothalamus \u2026 Elevated levels of oxytocin are associated with increased trust, cooperative behavior, sharing with strangers, the more effective reading of others\u2019 emotions, and more constructive conflict resolution.\u00a0<\/i><\/p>\n
That\u2019s from a federal lawsuit against solitary confinement. Lawyers bringing the decade-old suit, on behalf of inmates at a California maximum-security prison, argued that its practice of isolating inmates for years\u2014with an elaborate security system that nearly eliminated physical contact with others, even guards\u2014amounted to unconstitutional cruel and unusual punishment. Details of a settlement are still being fought over in court, but part of the permanent record now is the expert report written by University of California, Berkeley psychology professor Dacher Keltner, who for more than 15 years has been teaching and supervising research in the science of touch. \u201cIt\u2019s our earliest and, you could argue, our fundamental language of social connection,\u201d Keltner told me.<\/p>\n
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TACTILE NAVIGATION<\/span><\/p>\n\n
It may look like it has a head studying the ground beneath it, but this four-legged robot has no visual sensing. It scampers nimbly over uneven terrain, in part because its artificial intelligence responds to complex signals sent by air pressure pads on its feet. \u201cIt relies on touch to see an obstacle,\u201d says Ashish Kumar, an engineering graduate student at the University of California, Berkeley. Here Kumar prods the robot, built as a collaboration among scientists at Berkeley, Facebook, and Carnegie Mellon University.<\/span><\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/figcaption><\/figure>\n
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