Category: Medical Research & Technology

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Tiny Generators Tap Body Motion for Medical Applications

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Researchers have created biocompatible generators which harvest body motion to produce electrical impulses for medical applications such as wound healing.

Piezoelectric materials such as ceramics and crystals can generate an electrical charge when mechanically stressed, and are used in many devices such as ultrasound transducers, vibration sensors, and cell phones. In medicine, electrostimulation using piezoelectric devices has been shown to be beneficial for accelerating wound and bone fracture healing, maintaining muscle tone in stroke victims, and chronic pain reduction. However, lack of biocompatibility has stalled progress in the field.

Now bioengineers at the University of Wisconsin’s Department of Materials Science and Engineering, led by Professor Xudong Wang, have developed implantable piezoelectric therapeutic devices. These thin, flexible devices make use of the piezoelectric properties of non-rigid, nontoxic biological materials such as silk, collagen, and amino acids.
The team came up with a method for self-assembly of small patch-like constructs that use the amino acid lysine as the piezoelectric generator. The self-assembly process incorporates a biocompatible polymer shell that surrounds the lysine as the polymer/lysine solution evaporates. Chemical interactions between the inner layer of lysine and the polymer coating orient the lysine into the crystal structure necessary for it to produce electric current when flexed.

“This work is an outstanding example of using the chemical properties of the materials to create a self-assembling product,” explained David Rampulla, director of the Division of Discovery Science and Technology at the National Institute of Biomedical Imaging and Bioengineering. “The process used is rapid and inexpensive, making production of such wafers for therapeutic applications feasible. That the wafers are biodegradable opens the possibility for creating electrotherapies that could be used to accelerate healing of an injured bone or muscle, for example, and then degrade and disappear from the body.”

In one of a number of tests, wafers were placed in the leg and chest of rats, movements of which compressed the piezoelectric wafers enough to create an electrical output. Blood tests performed after the transplanted wafer dissolved showed normal levels of blood cells and other metabolites, indicating no harmful effects from the dissolved device.

Prof Wang emphasises the simplicity of the elegant work. “We believe the technology opens a vast array of possibilities including real-time sensing, accelerated healing of wounds and other types of injuries, and electrical stimulation to treat pain and other neurological disorders. Importantly, our rapid self-assembling technology dramatically reduces the cost of such devices, which has the potential to greatly expand the use of this very promising form of medical intervention.”

The results were reported in the journal Science.

Source: Medical Xpress

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Doctor’s Presence During BP Measurement Triggers Flight-or-fight Response

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Photo by Thirdman from Pexels
Photo by Thirdman from Pexels

A small study has shown that a doctor’s presence during a blood pressure measurement skews the results, according to researchers who studied the effect by measuring nerve activity.

The phenomenon known as ‘white coat hypertension‘ is where the mere presence of a medical professional can raise blood pressure. Known about for decades, it occurs in about a third of patients.

In a small study published in the journal Hypertension, researchers probed the effect by measuring blood pressure, heart rate and nerve traffic in the skin and muscles with and without a doctor present.

The researchers found a “drastic reduction” in the body’s alarm response when a doctor was not present, said co-lead author Dr Guido Grassi, professor of internal medicine at the University of Milano-Bicocca.

Blood pressure and heart rate increases in response to a perceived threat, said Dr Meena Madhur, associate professor of medicine in the divisions of clinical pharmacology and cardiology at Vanderbilt University.

“If you’re out in the wild and a bear was charging after you, you’d want your blood vessels in your skin, for example, to constrict and the blood vessels in your muscles to dilate to provide more blood flow to those organs so that you can run really fast,” said Prof Madhur, who was not involved in the new research.

The study included 18 people, 14 of them men, with untreated mild to moderate hypertension. Each participant was examined in a lab, where an electrode measured nerve activity in the skin and muscles. Readings were taken twice in the presence of a doctor and twice without.

Both blood pressure and heart rate rose when the doctor was present, with nerve traffic patterns to the skin and skeletal muscle suggesting a classic fight or flight reaction.

Without the doctor’s presence, cardiovascular and neural responses were “strikingly different,” the researchers wrote. Fight or flight response indications were “entirely absent”.

Peak systolic blood pressure was an average of 14 points lower when the participant was alone than when a doctor was present, and peak heart rate was lowered by nearly 11 beats per minute.

This was the first study to actually measure sympathetic nervous system responses to doctors supervising a blood pressure measurement, the researchers wrote.

The study’s findings illustrated the complexity of blood pressure measurement and how it is affected by involuntary nervous system reactions, Grassi said. “Measurements without the doctor’s presence may better reflect true blood pressure values.”

White coat hypertension is not a new concept, Prof Madhur said, “this just drives home the fact that we should be more conscious of how the blood pressure is taken in the clinic.”

Last year, the American Medical Association and AHA issued a joint report endorsing more blood pressure measurement at home.

Limitations included the small study size due to the complexity of the measurements, the researchers said. Subsequent research would need to examine blood pressure medication as they could affect the fight or flight response, said Orof Madhur.

The work needs to be repeated with more women to examine possible sex differences. And she’d be interested in seeing whether people have the same response to nurses and other medical professionals as they did to doctors in this study.

Previous work shows that when nurses take blood pressure measurements, the white coat effect is reduced.

This latest research emphasises the need for people to handle blood pressure measurements with care, Prof Madhur said.

“I always tell my patients that we really can’t rely on a single office blood pressure measurement, because that’s just a random point in time,” she said.

Prof Madhur said that to take an accurate reading at home, a patient should sit still, with their back straight and supported and feet on the floor, waiting at least a few minutes before recording blood pressure. They should take multiple readings at the same time of day over the course of a week, and bring that log to their doctor’s appointment. Those at-home readings should be the ones used for planning treatment, she said.

“But,” Prof Madhur added, “if we are going to do an office blood pressure reading, it should be taken with the doctor not in the room.”

Source: American Heart Association

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New Bacteriophage Could Combat C. Diff

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A bacteriophage. Credit: NIAH

A group of newly discovered bacteriophages named after the UK village of Colney could help combat C. difficile infections.

Clostridioides difficile, or C. diff, is a species of bacteria that infects the human gut. It can become a major problem when our normal gut microbes are impaired, most commonly during a course of antibiotics. This leads to an overgrowth of C. diff, with toxins it produces causing diarrhoea and severe inflammation.

Treatment involves further courses of antibiotics, but relapse and recurrent infections are common. The strains are becoming more resistant to antibiotics and causing more severe illness.

This prompted researchers in Norwich to look for the bacteria’s natural enemy, bacteriophages. They screened 27 different C. diff strains for any bacteriophages, finding one, which they called ΦCD27 (phiCD27). Genome sequencing confirmed this phage had not been discovered before. In fact, the members of the International Committee on Taxonomy of Viruses (ICTV) decided it was genetically distinct enough to form a new group, or genus of phages.

The ICTV decided to name the new genus Colneyvirus, the Colney parish address of the Institute of Food Research (IFR, now part of Quadram Institute), where it was first discovered.

Like normal viruses, phages reproduce by injecting their genetic material into bacteria, making viral copies using the host’s own machinery. Using enzymes called endolysins, they destroy the bacterial cell wall and escape.

The researchers extracted the gene for ΦCD27’s endolysin and put it into another bacterium, E. coli so that they could produce and purify the endolysin. It was proven active against 30 different C. diff strains, including hypervirulent strains behind the current epidemic. It also didn’t affect other common bacterial species in the human gut microbiome.

”This phage and the endolysin encoded by its genome can provide a targeted approach to combat C. diff infections, in contrast to use of broad spectrum antibiotics that cause collateral damage by inhibiting other members of the gut bacterial population” said Professor Arjan Narbad, Group Leader at the Quadram Institute.

However, to be effective the endolysins need to be delivered into the gut, so the team also put the gene into a strain of lactic acid bacteria that has previously been used to deliver proteins and vaccines to the gut.

The research team believes this could serve as the basis for future new treatments C. diff. The system needs more work, but in the battle against this bacterial pandemic, the colneyvirus could be a vital ally.

Source: Quadram Institute

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Exact Location of Body’s Blood Pressure Sensors Finally Revealed

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Credit: CC0

After 60 years of fruitless searches by scientists, researchers from the University of Virginia have finally determined the location of our bodies’ natural blood-pressure sensors.

These cellular sensors monitor blood pressure and adjust hormone levels to keep it in check. Scientists have long suspected that these ‘baroreceptors’, may exist in or around specialised kidney cells called renin cells, but no one has been able to locate the baroreceptors within the cell until now.

The new findings, from UVA Health’s Dr Maria Luisa S Sequeira-Lopez and colleagues, finally reveal where the barometers are located, how they work and how they help prevent hypertension or hypotension. The study was published in Circulation Research.

“It was exhilarating to find that the elusive pressure-sensing mechanism, the baroreceptor, was intrinsic to the renin cell, which has the ability to sense and react, both within the same cell,” said Dr Sequeira-Lopez. “So the renin cells are sensors and responders.”

Back in 1957, it was first proposed that a pressure sensor existed inside renin cells because the cells had to know when to release renin, a hormone that helps regulate blood pressure. Though the baroreceptors had to exist, scientists couldn’t tell what it was and whether it was located in renin cells or surrounding cells.

To tackle this decades-old mystery, the study’s researchers used a combination of innovative lab models and determined that the baroreceptor was a ‘mechanotransducer’ inside renin cells. This mechanotransducer detects pressure changes outside the cell, then transmits these mechanical signals to the cell nucleus, akin to how the cochlea turns sound vibrations into nerve impulses.

Through in vitro tests, the researchers found that applying pressure to renin cells triggered changes within the cells and decreased activity of the renin gene, Ren1. The scientists also compared differences in gene activity in kidneys exposed to lower pressure and those exposed to higher pressure.

Ultimately, when the baroreceptors detect excess pressure outside the renin cell, renin production is cut back, while low blood pressure prompts more renin production.

Dr Sequeira-Lopez said she is looking forward to the work to “unravel the signaling and controlling mechanisms of this mechanotransducer and how we can use the information to develop therapies for hypertension.”

Source: University of Virginia

Categories : General Interest Medical Research & TechnologyTags :

Boy Walks With Help of A Robotic Exoskeleton his Father Designed

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Photo by Rachel Kuo on Unsplash

Though it’s not quite as fantastic as Iron Man’s super-powered exoskeleton, a robotic exoskeleton designed by his father’s company helps 16 year old Oscar Constanza to walk. Oscar has a genetic neurological condition that means his nerves do not send enough signals to his legs.

Fastened to his shoulders, chest, waist, knees and feet, the exoskeleton enables Oscar to walk across the room and turn around. The exoskeleton is a voice-operated robot, responding to the user’s verbal commands, rather than other designs which respond to user movements or nerve signals.

“Before, I needed someone to help me walk … this makes me feel independent,” said Oscar.

His father Jean-Louis Constanza is one of the co-founders of the company that makes the exoskeleton, which is called Atalante.

“One day Oscar said to me: ‘dad, you’re a robotic engineer, why don’t you make a robot that would allow us to walk?’” his father recounted
“Ten years from now, there will be no, or far fewer, wheelchairs,” he said.

Exoskeletons are being produced around the world, with a wide variety of applications including, the military, industrial work and in healthcare to help nurses move and position patients. During the COVID pandemic, they have even been evaluated for use in the physically taxing task of prone positioning of COVID patients in ICU wards. Some, like Wandercraft’s model, are designed to help people with mobility problems to walk.

Since most are still quite heavy, manufacturers are competing to make them as light and usable as possible.

Wandercraft’s Atalante exoskeleton, which is an outer frame that supports but also simulates the movement of the wearer’s body, has been sold to dozens of hospitals in France, Luxembourg and the United States, with a unit price of about $176 000, said Constanza. The Atalante exoskeleton is currently aimed at use in physical rehabilitation in stroke and spinal cord injury patients.

At the moment, it cannot be bought by private individuals for everyday use – but the Wandercraft engineers are working on this as the design would need to be much lighter.

Source: New York Post

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Artificial Sweetener Delivers a Protective Carbon Monoxide Dose

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Photo by Sharon McCutcheon on Unsplash
Photo by Sharon McCutcheon on Unsplash

An oral prodrug has been developed which uses artificial sweeteners to deliver a protective carbon monoxide dose which protects against acute kidney injury.

Although carbon monoxide (CO) gas is toxic in large doses, with some 50 000 people suffering CO poisoning each year in the US, scientists have discovered it can reduce inflammation and protect cells against injury. The  protective effects of CO against injury in the kidneys, lungs, gastrointestinal tract and liver, among other organs has been shown in previous research. For the past five years, Wang and his collaborators have worked to design a safe way to deliver CO to human patients via prodrugs, which are inactive compounds that must undergo a chemical process in the body to release the active pharmacological agent. Their paper was published in Chemical Science.

Using two common artificial sweeteners, saccharine and acesulfame, as ‘carrier’ molecules for a prodrug, Prof Wang’s team were able to create an oral administration route for CO. They designed the molecules to release CO as they decomposed from water exposure. These are the first examples of orally active, organic CO prodrugs using a benign carrier that is approved by the Food & Drug Administration with a demonstrated safety profile.

“It’s difficult to deliver a gas, much less a poisonous gas, as a therapeutic to patients, and this work represents a pivotal step forward in developing alternative delivery forms,” said Prof Wang, a Georgia Research Alliance Eminent Scholar. “We wanted to work with a carrier that has a very well characterized safety profile, which confers a higher degree of certainty that it will be safe to use in a pill for human consumption.”

The scientists tested one of the prodrugs, CO-306, for pharmacological efficacy against acute kidney damage. CO-306, which uses saccharine as a carrier molecule, was administered to mice and it was found that it reduced biomarkers for kidney injury, indicating it could be developed working therapy. The type of kidney injury modelled mimicked those in humans that occur with extensive muscle damage, sickle cell disease, a common type of malaria, cardiopulmonary bypass surgery and severe sepsis.

Further animal model studies and safety assessments on CO-306 are planned by Wang and colleagues before they progress to human clinical studies. They also plan to test CO-306 for efficacy against other types of organ injuries.

Additionally, CO-based therapies hold promise as a method of reducing the likelihood of organ damage during transplantation and improving outcomes for transplant patients, according to Prof Wang.

“Science shows that exposing organs to CO gas can help preserve organs and prevent them from deteriorating during the process of transplantation,” he said. “Now we need to demonstrate that these prodrugs can have a similar effect.”

Source: Georgia State University

Journal information: De La Cruz, L. K., et al. (2021) Adapting decarbonylation chemistry for the development of prodrugs capable of in vivo delivery of carbon monoxide utilizing sweeteners as carrier molecules. Chemical Science. doi.org/10.1039/D1SC02711E.

Categories : Medical Research & Technology Neurodegenerative DiseasesTags :

MRI and Ultrasound Combo Opens Blood-brain Barrier

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In a mouse model study of MRI-guided focused ultrasound-induced blood-brain barrier (BBB) opening at MRI field strengths ranging from ­approximately 0 T (outside the magnetic field) to 4.7 T, the static magnetic field dampened the detected microbubble cavitation signal and decreased the BBB opening volume. Credit: Washington University School of Medicine in St. Louis

Using a combination of ultrasound, MRI field strength and microbubbles can open the blood-brain barrier (BBB) and allow therapeutic drugs to reach the diseased brain location with MRI guidance. 

Using the physical phenomenon of cavitation, it is a promising technique that has been shown safe in patients with various brain diseases, such as Alzheimer’s diseases, Parkinson’s disease, ALS, and glioblastoma.
While MRI has been commonly used for treatment guidance and assessment in preclinical research and clinical studies, until now, researchers did not know the impact that MRI scanner’s magnetic field had on the BBB opening size and drug delivery efficiency.

Hong Chen, associate professor of biomedical engineering at Washington University in St. Louis, and her lab have found for the first time that the magnetic field of the MRI scanner decreased the BBB opening volume by 3.3-fold to 11.7-fold, depending on the strength of the magnetic field, in a mouse model. The findings were in Radiology.

Prof Chen conducted the study on four groups of mice. After they were injected microbubbles, three groups received focused-ultrasound sonication at different strengths of the magnetic field: 1.5 T (teslas), 3 T and 4.7 T, and one group was never exposed to the field. 

The researchers found that the microbubble cavitation activity, or the growing, shrinking and collapse of the microbubbles, decreased by 2.1 decibels at 1.5 T; 2.9 decibels at 3 T; and 3 decibels at 4.7 T, compared with those that had received the dose outside of the magnetic field. Additionally, the magnetic field decreased the BBB opening volume by 3.3-fold at 1.5 T; 4.4-fold at 3 T; and 11.7-fold at 4.7 T. No tissue damage from the procedure was seen.

Following focused-ultrasound sonication, the team injected a model drug, Evans blue dye, to investigate whether the magnetic field affected drug delivery across the BBB. The images showed that the fluorescence intensity of the Evans blue was lower in mice that received the treatment in one of the three strengths of magnetic fields compared with mice treated outside the magnetic field. The Evans blue trans-BBB delivery was decreased by 1.4-fold at1.5 T, 1.6-fold at 3.0 T and 1.9-fold at 4.7 T when compared with those treated outside of the magnetic field.

“The dampening effect of the magnetic field on the microbubble is likely caused by the loss of bubble kinetic energy due to the Lorentz force acting on the moving charged lipid molecules on the microbubble shell and dipolar water molecules surrounding the microbubbles,” said Yaoheng (Mack) Yang, a doctoral student in Prof Chen’s lab and the lead author of the study.

“Findings from this study suggest that the impact of the magnetic field needs to be considered in the clinical applications of focused ultrasound in brain drug delivery,” Prof Chen said.

In addition to brain drug delivery, cavitation is also used in several other therapeutic techniques, such as histotripsy, the use of cavitation to mechanically destroy regions of tissue, and sonothrombolysis, a therapy used after acute ischaemic stroke. The magnetic field’s damping effect on cavitation is expected to affect the treatment outcomes of other cavitation-mediated techniques when MRI-guided focused-ultrasound systems are used.

Source: Washington University in St. Louis

Journal information: Yang, Y., et al. (2021) Static Magnetic Fields Dampen Focused Ultrasound–mediated Blood-Brain Barrier Opening. Radiology. doi.org/10.1148/radiol.2021204441. 

Categories : Implants and Prostheses Medical Research & TechnologyTags :

Carbon Fibre Electrodes Allow Unprecedented Neural Recording

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Image by Robina Weemeijer on Unsplash

A tiny, implantable carbon fibre electrode has the potential to provide a long-term brain-computer interface which can record electrical signals over lengthy periods of time.

The carbon fibre electrodes were developed at the University of Michigan and demonstrated in rats. The new research shows the promise of carbon fibre electrodes in recording electrical signals from the brain without damaging brain tissue. Directly implanting carbon fiber electrodes into the brain allows the capturing of bigger and more specific signals than current technologies.

This technology could lead to advances that could give amputees and those with spinal injuries control of advanced prosthetics, stimulate the sacral nerve to restore bladder control, stimulate the cervical vagus nerve to treat epilepsy and provide deep brain stimulation as a possible treatment for Parkinson’s.  

“There are interfaces out there that can be implanted directly into the brain but, for a variety of reasons, they only last from months to a few years,” said Elissa Welle, a recent PhD graduate from the U-M Department of Biomedical Engineering. “Any time you’re opening up the skull for a procedure involving the brain, it’s a big deal.”

Brain implants are typically made from silicon due to its ability to conduct electricity and its historic use in cleanroom technology. But silicon is not very biocompatible and leads to the formulation of scar tissue over long periods. Such electodes will eventually degrade and no longer capture brain signals, requiring removal.

Carbon fibres may be the answer to getting high-quality signals with an interface that lasts years, not months. And by laser cutting and sharpening carbon fibers into tiny, subcellular electrodes in the lab with the help of a small blowtorch, U-M engineers have harnessed the potential for excellent signal capture in a form the body is more likely to accept.

“After implantation, it sits inside the brain in a way that does not interfere with the surrounding blood vessels, because it’s smaller than those blood vessels,” Welle said. “They’ll move around and adjust to an object that small, rather than get torn as they would when encountering larger implants.”

Part of the electrode’s compatibility in brain tissue is down to smaller size, but its needle-like shape may also minimise compacting of any surrounding tissue. Larger carbon-based electrodes have been shown to actually encourage neural tissue to grow instead of degrading. The team is hopeful that similar potential for their carbon fibre electrodes will be revealed by further testing.

Carbon fibre electrodes in a previous study dramatically outperformed conventional silicon electrodes with 34% of electrodes recording a neuron signal compared to 3%. Laser cutting then improved this number to 71% at 9 weeks after implantation. Flame sharpening has now enabled these high performance probes to be implanted directly into the cerebral cortex, negating the need for a temporary insertion aid, or shuttle, as well as into the rat’s cervical vagus nerve.

It is relatively easy to insert electrodes into the brain. But the researchers have also taken on the more difficult task of inserting the sharpened carbon fibre electrodes into nerves, with micrometre diameters.

Those findings show that potential for these electrodes goes beyond prosthetic manipulation, according to Cindy Chestek, a U-M associate professor of biomedical engineering, and principal investigator of the The Cortical Neural Prosthetics Lab.

“Someone who is paralysed may have no control over things like their bladder, for example,” Prof Chestek said. “We may be able to utilise these smaller electrodes to stimulate and record signals from areas that can’t be reached by larger ones, maybe the neck or spinal cord, to help give patients some level of control.”

Source: University of Michigan

Categories : Hospitals Medical Research & TechnologyTags :

Research Shows Surgical Simulation Training Improves Performance

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Photo by Tim Cooper on Unsplash

Success with independent surgical simulation training has made it the new normal for students at the Pan Am Clinic.

Traditionally, surgical resident training has been master–apprentice-type relationship, with gradually increasing responsibilities until the trainees can do procedures on their own. Given recent pressures in the health care system, including reduced operating room time, increased difficulty of procedures and working hour restrictions, there is less time for residents to learn using the traditional method.

Surgical simulation, a surprisingly old system, dates back nearly 2500 years, when they were first used to plan innovative procedures while maintaining patient safety. One of the first recorded instances of surgical simulation was the use of leaf and clay models in India around 600 BC to conceptualise nasal reconstruction with a forehead flap

In a recent study, researchers from the University of Manitoba and the Pan Am Clinic recently examined the effectiveness of a mixed reality simulator for the training of arthroscopy novices.

Study author Dr Samuel Larrivée said: “Sports surgeons at our institution noted anecdotally that junior residents had difficulty reaching competency in arthroscopic skills by the end of their three-month rotation, and were not as prepared when starting their senior rotation. There was a need to increase training opportunities outside of the operating room in order to prepare our residents for independent practice.”

Prior to obtaining the ArthroS™ simulator, the University of Manitoba Orthopedic Surgery program occasionally made use of options such as benchtop dry simulators, cadavers and an older generation simulator with active haptics. These largely complemented academic teaching sessions in small groups with some success, and were available for use by residents as needed. But, due to the low fidelity and difficult setup, few residents took advantage of it.

However, medical students readily took to the ArthroS simulator. Alisha Beaudoin, a co-author and medical student, attested to her experience using the ArthroS simulator in her early training. “I found this training to be very helpful during my surgery rotation. Many of my preceptors were impressed by my superior arthroscopic and laparoscopic skills. This training may allow students with an interest in surgery to be more prepared.

“Recently, many Canadian universities have moved to competency-based curriculums where residents must demonstrate competency prior to moving to the next defined practice level. The study noted that this is similar to the training available on VirtaMed ArthroS and that “a user enrolled in the mentoring program is progressed through various levels of training by meeting training targets, essentially providing a proficiency-based progression.”

This paper is the first in what the authors hope is a larger body of work on validating arthroscopy simulators for resident training. There are currently plans to repeat similar studies with the other modules (hip, shoulder, and ankle), with larger sample sizes, and at different levels of training.

Participants were split into three groups: simulator training only, mentor-based training, and a control. After  four weeks, surgical performance improved among both traditional and simulator-based training groups. The study concluded that “simulator training may provide enhanced skills to improve patient safety overall, as residents may become more skilled earlier in their training, leaving more time for the mentor to teach more advanced skills.” Dr Beaudoin further explains: “I believe that simulation training should be introduced into the standardised curriculum because I believe it offers a safe space to hone your skills and improve in a stress-free environment.”

On the strength of the results, the residency programme has made it a requirement in the curriculum that residents in their sports rotation complete the self-learning modules. Dr Larrivée believes this will help residents develop their triangulation skills and memorise the steps ahead of their first surgery, and to consolidate their knowledge.

Source: VirtaMed

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A Step to Towards Electrically Restoring Oral Sensation and Function

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Photo by Maria Lysenko on Unsplash

In an effort towards restoring oral functionality lost to nerve or brain damage, researchers at Texas A&M University have determined the minimum electrical stimulation needed to provide sensation in various parts of the mouth.

Sensorimotor feedback loops involve the brain interpreting incoming signals from sensory nerves and then ordering motor nerves to execute a particular movement. Sensorimotor loops play a vital role in voluntary functions, like walking or holding an object, and involuntary movements, like sneezing or blinking.

Within the mouth, both sensory and motor nerves are richly supplied. In particular, sensorimotor nerves in the soft palate and tongue coordinate several intraoral movements related to swallowing, speech and respiration. Damage to either the sensory or motor nerve fibres due to neurotrauma or disease can therefore compromise these essential functions and worsening the quality of life for afflicted individuals.

Electrical nerve stimulation might help jumpstart the nerves into action, much like how a pacemaker can electrically stimulate nerves in the heart, causing the heart muscle to contract. Unlike a pacemaker however, the parameters of the electrical currents needed for proper stimulation of different parts of the mouth have not been investigated.

“Electrical stimulation can modulate nerve currents or action potentials, which are the mode of communication to and from the brain,” said Hangue Park, assistant professor in the Department of Electrical and Computer Engineering. “And so, electrical stimulation should be carefully applied, because if not, then it might cause undesirable effects, or it might not stimulate anything at all.”

To investigate the minimum stimulation currents needed, Park and his team place tiny metal electrodes in a standard dental retainer. These electrodes were positioned in subjects’ mouths to stimulate either their soft palate or the side and tip of the tongue, which are dense in sensory nerves. The researchers slowly changed the amplitude of the stimulation current, keeping the frequency fixed. Subjects reported when they began feeling a sensation and when the sensation was uncomfortable, and the same experiment was repeated with a higher frequency of current.

After compiling their data, the team determined the average perception and discomfort thresholds for the tongue and soft palate. In addition, they produced an equivalent circuit of the intraoral cavity to duplicate the electrical properties of that area. This circuit, the researchers said, can help to further study the effects of electrical stimulation offline without requiring human subjects.

The researchers noted that their next steps would be to electrically stimulate the intraoral region and investigate how these simulations change chewing, swallowing and other behaviours.

“Sensorimotor systems can be extremely vulnerable to damage due to neural defects, aging and neurodegenerative diseases,” Park said. “In this study, we have begun to lay the groundwork for electrically stimulating parts of the mouth that control involuntary and voluntary movements. Our work is a seminal study and it is important so that we can, in the near future, help people that face enormous challenges doing everyday tasks that we take for granted.”

Source: Texas A&M University

Journal information: Park, B., et al. (2021) Electrical Characterization of the Tongue and the Soft Palate using Lumped-Element Model for Intraoral Neuromodulation. IEEE Transactions on Biomedical Engineering. doi.org/10.1109/TBME.2021.3070867.