Forests recovering from logging act as a source of carbon

Peer-Reviewed Publication

IMPERIAL COLLEGE LONDON

 

IMAGE: LOGGING EXTRACTION IN THE BORNEAN RAINFOREST view more 

CREDIT: ZOE G DAVIES

Tropical forests recovering from logging are sources of carbon for years afterwards, contrary to previous assumptions, finds a new study.

Tropical forests that are recovering from having trees removed were thought to be carbon absorbers, as the new trees grow quickly. A new study, led by Imperial College London researchers, turns this on its head, showing that the carbon released by soil and rotting wood outpaces the carbon absorbed by new growth.

The researchers say the result highlights the need for logging practices that minimise collateral damage to improve the sustainability of the industry. The study, which monitored carbon in forests in Malaysian Borneo as part of the Stability of Altered Forest Ecosystem (SAFE) Project, is published today in Proceedings of the National Academy of Sciences.

First author Maria Mills, who began the work at Imperial and completed it at the University of Leicester, said: “Our results show that for the tropical forest we studied, logged areas are a source of carbon even a decade after logging has occurred. This means we need to reassess their role in global carbon budgets – we can no longer apply the blanket assumption that they are carbon sinks.”

Lead researcher Dr Terhi Riutta, now at the University of Exeter, said: “A lot of the carbon released in recovering forests is from collateral damage – trees that have died as a result of damage during the logging operations left to rot, and from disturbed soil. Logged forests still have value – we know they have a unique biodiversity – so making sure they are also not releasing extra carbon through better logging practices will boost their sustainability.”

Many previous studies of recovering forests have focused on measuring tree growth to estimate the amount of carbon taken from the atmosphere. The new study also measured how much carbon was coming from the ground (soil and dead wood) to calculate the carbon budget from the incoming and outgoing carbon flows for logged and unlogged (old-growth) forest.

Logged forest plots in the study had experienced logging at different stages over the prior few decades. The measurements were taken between 2011 and 2017.

To measure the carbon released from the ground, researchers used a portable carbon dioxide monitor to test patches of ground and pieces of deadwood in several plots monthly for several years. The team had also set up a 52-metre-tall tower above the forest canopy to continuously measure the ‘flux’ of carbon into and out of the forest to see whether it was a net source or sink of carbon.

They found that unlogged forested areas are generally carbon neutral, but that moderately and heavily logged tropical forest areas are a carbon source. They estimate an average carbon source of 1.75 +/- 0.94 tonnes of carbon per hectare within moderately logged plots and 5.23 +/- 1.23 tonnes of carbon per hectare in severely degraded plots, with emissions continuing at these rates for at least one decade after logging.

Co-author Professor Rob Ewers, from the Department of Life Sciences at Imperial, said: “The measurements from the tower show us whether the forest area is a source or a sink of carbon, and the soil monitoring tells us why this is. From these measurements, we know logged forests are still a source of carbon up to a decade after they have been logged, and that this primarily comes from organic matter in the soil or from rotting wood.”

The team say carbon monitoring should be conducted in other forests in different regions to build a more accurate picture of how logged forests contribute to global carbon budgets.

Eddy covariance flux tower over a heavily logged tropical forest landscape within the Stability of Altered Forest Ecosystem (SAFE) Project (this is the tower used within this study)

CREDIT

Maria Mills

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JOURNAL

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2214462120 

ARTICLE TITLE

Tropical forests post-logging are a persistent net carbon source to the atmosphere

ARTICLE PUBLICATION DATE

9-Jan-2023

Broccoli looks more like cauliflower in a warmer world

Peer-Reviewed Publication

CORNELL UNIVERSITY

ITHACA, N.Y. – As seasoned gardeners know, broccoli heads don’t develop properly and can resemble cauliflower when grown in higher temperatures.

A new study identifies the genetic underpinnings for why broccoli heads become abnormal when it’s hot, providing insight into effects of climate-induced warming for all crops and pointing the way for breeding heat-resistant new varieties.

Broccoli grows best when planted in cool early spring or late summer, into fall. The researchers found that while broccoli grows normally at average temperatures of 61 degrees Fahrenheit, its crowns begin to deform at 72 degrees F and it forms dense cauliflower-like heads (called curds) at 82 degrees F.

The researchers then applied 5-azacytidine, a chemical known to inhibit a process called DNA methylation, where a methyl group – a small molecule – gets added to DNA. Methylation is one mechanism for turning genes on and off; in this case it suppresses a cluster of genes required for normal broccoli head production. When 5-azacytidine was administered, normal broccoli heads grew even at 82 degrees F, suggesting that methylation was behind the abnormal growth in the presence of heat. 

“Once we understand the mechanism better, we should be able to devise ways to develop a new biotechnology, a molecular genetics approach to suppress DNA methylation, in order to breed crops to grow in much warmer temperatures and in wider regions,” said Susheng Gan, Cornell University professor in the College of Agriculture and Life Sciences, and a co-corresponding author of the paper published Dec. 22 in the journal Molecular Horticulture. Liping Chen, a professor of vegetable science at Zhejiang University in Hangzhou, China, is the other corresponding author.    

Warming temperatures impact all aspects of growth and development in plants. Flower development is especially complex and sensitive to temperatures, with heat reducing the quality and yield of vegetables such as broccoli where the complete flower head – including stems, stalks, leaves and flowers – is eaten. Though more study is needed, Gan believes that at higher temperatures, DNA methylation of genes involved in floral development may be conserved across all crops. 

In the study, the researchers profiled broccoli plants (Brassica oleracea) using whole-genome sequencing technologies that identified the plant’s methylome – where in the genome methylation occurred – and its transcriptome – which identifies which genes are turned on. They found that abnormal flower development in broccoli was regulated by sets of floral development cessation-associated genes (FCGs). At 61 degrees F, broccoli heads (its floral bud) developed normally. At 82 degrees F and to a lesser extent at 72 degrees F, methylation of genetic elements that turned on FCGs were suppressed.

When grown at warmer temperatures, floral development becomes restricted to earlier stages of development. So, at 72 degrees F, broccoli buds are restricted to a stage where they look like a cross between a broccoli head and cauliflower curd; and at 82 degrees, they are even further undeveloped, and resemble a cauliflower-like curd.

Future studies will examine the mechanism behind DNA methylation of FCGs at high temperatures.

Zilei Yao and Lu Yuan, both at Zhejiang University, are co-first authors of the study. 

For additional information, see this Cornell Chronicle story.

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JOURNAL

Molecular Horticulture

DOI

10.1186/s43897-022-00047-8 

ARTICLE TITLE

Warming-induced changes of broccoli head to cauliflower-like curd in Brassica oleracea are regulated by DNA methylation as revealed by methylome and transcriptome co-profiling

U$A

Private equity changes workforce stability in physician-owned medical practices

Study reveals more churn in workforce, greater reliance on physician assistants

Peer-Reviewed Publication

OREGON HEALTH & SCIENCE UNIVERSITY

New research reveals private equity firms that acquire physician-owned medical practices experience greater replacement of the workforce and rely more heavily on advanced practice providers — such as physician assistants and nurse practitioners — rather than physicians.

The study is the first to characterize the shift in workforce composition following private equity acquisition. It was published today in the January issue of the journal Health Affairs by researchers at Oregon Health & Science University, the University of Chicago, Harvard University and Johns Hopkins University.

The impacts come amid well-documented shortages in the overall health care workforce exacerbated by the COVID-19 pandemic.

“We really ought to be paying more attention to how these big-picture practice delivery shifts are affecting physicians,” said senior author Jane Zhu, M.D., assistant professor of medicine (general internal medicine and geriatrics) in the OHSU School of Medicine in Portland. “There is a finite number of us. If the measures we found in this study suggest dissatisfaction among physicians, then ultimately that’s yet another burden on a workforce that is already on the brink of burnout.”

The findings are the latest in a line of research to suggest private equity firms are increasing pressure to maximize profits.

“A lot of the current research on private equity looks at changes in costs, revenue or services following acquisitions. The purpose of this study was to capture private equity in the context of the clinical workforce,” said first author Joseph Dov Bruch, Ph.D., assistant professor of public health sciences at the University of Chicago. “That we observe greater clinician replacement at private equity-acquired practices compared with non-private equity-acquired practices suggests that private equity’s business strategy may differ from that of traditional practice owners.”

Researchers did not specifically examine the effect of the changes in workforce composition on health outcomes or patient care, although the study cites previous research that suggests patient care suffers with a more transitory workforce.

“A more stable workforce is associated with better health outcomes for patients, improved quality metrics, and reduced resource use,” they write.

The study identified 213 private equity-acquired practices in dermatology, ophthalmology and gastroenterology, and compared them with 995 physician-owned practices in those same specialties. They found that physicians in private equity-acquired practices were more likely than their counterparts in physician-owned practices to both enter and leave a practice.

The study also documented growth of advanced practice provider staffing in private equity-acquired practices.

“Private equity maximizes profits by increasing revenues or cutting costs,” Zhu said. “Shifting toward ancillary service providers and advanced practice providers is one way to accomplish both of those things.”

In addition to Zhu and Bruch, co-authors include Canyon Foot of OHSU; Yashaswini Singh, M.P.A., and Daniel Polsky, Ph.D., M.P.P., of Johns Hopkins; and Zirui Song, M.D., Ph.D., of Harvard.

This study was supported by the National Institute for Health Care Management (NIHCM) Foundation (to Jane Zhu). The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

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JOURNAL

Health Affairs

DOI

10.1377/hlthaff.2022.00308 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Workforce Composition In Private Equity–Acquired Versus Non– Private Equity–Acquired Physician Practices

ARTICLE PUBLICATION DATE

9-Jan-2023

Families with food insecurity have greater health care expenditures

Peer-Reviewed Publication

ATRIUM HEALTH WAKE FOREST BAPTIST

 

IMAGE: DEEPAK PALAKSHAPPA, M.D., ASSOCIATE PROFESSOR OF GENERAL INTERNAL MEDICINE AT WAKE FOREST UNIVERSITY SCHOOL OF MEDICINE view more 

CREDIT: WAKE FOREST UNIVERSITY SCHOOL OF MEDICINE

WINSTON-SALEM, N.C. – Jan. 9, 2023 – Food insecurity, which is the limited or uncertain availability of nutritionally adequate and safe food, impacts about 10.2% of U.S. households, according to the U.S. Department of Agriculture Economic Research Service. In families with children in the home, food insecurity is even higher, at 12.5%.

Previous studies have shown an association between food insecurity and individual health care expenditures, but there is little research on how food insecurity impacts families’ health care use.

Now, researchers at Wake Forest University School of Medicine are reporting the results of a new study that shows food-insecure families have higher health care expenditures than families that are food secure.

The study was released today in the January issue of Health Affairs.

“We know that food insecurity has a negative impact on individual health outcomes,” said Deepak Palakshappa, M.D., associate professor of general internal medicine at Wake Forest University School of Medicine and principal investigator of the study. “But we need a better understanding of the financial implications on families and health care expenditures.”

In the retrospective study, Palakshappa’s team sought to determine the association between a family’s food insecurity over the course of one year and their health care expenditures throughout the following year. Researchers analyzed data from the 2016 and 2017 Medical Expenditure Panel Survey, a large-scale survey conducted annually by the Agency for Healthcare Research and Quality that is representative of the U.S. population. The survey collects information from U.S. medical providers about health care services, health insurance, expenditures and sociodemographic characteristics.

The team collected data on 14,666 individuals from 6,621 families and found that food-insecure families had 20% greater total health care expenditures than food-secure families, an annual difference of about $2,456.

“We found that food insecurity in 2016 was associated with increased care expenditures in 2017 among families regardless of insurance coverage type,” Palakshappa said.

The results also have significant implications for any potential programs or policies aimed at addressing food insecurity.

“Interventions that address food insecurity in one or more specific family members may also provide benefits to others in the home,” Palakshappa said. “And there’s a potential financial benefit for insurers to invest in these programs.”

Palakshappa’s team also found that 1 in 5 families had more than one insurance plan, making it challenging to determine the full financial benefit of food insecurity interventions in households with mixed insurance coverage.

“More parents are enrolling their children in Medicaid or CHIP instead of their employer-sponsored health insurance because of increased out-of-pocket expenses,” Palakshappa said. “However, the expansion of public subsidies such as the Supplemental Nutrition Assistance Program or child tax credits can alleviate food insecurity.”

Palakshappa said additional research is needed to evaluate how addressing food insecurity at an individual patient visit may affect the health outcomes and health care utilization of other family members.

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JOURNAL

Health Affairs

DOI

10.1377/hlthaff.2022.00414 

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Food Insecurity Was Associated With Greater Family Health Care Expenditures In The US, 2016–17

ARTICLE PUBLICATION DATE

9-Jan-2023

UK

Mobility specialists looking to quit profession

Study reveals a third of orthotists working privately and in NHS seek a way out

Peer-Reviewed Publication

ANGLIA RUSKIN UNIVERSITY

More than a third of orthotists, specialists who improve quality of life for people with long term conditions and disabilities, would leave the profession if they could, according to a new study.

Orthotists provide gait analysis to patients and design and fit external devices. These include insoles, braces and splints, to support and improve posture, function and mobility and manage pain and deformity.

However, new research by Anglia Ruskin University (ARU) has found that 37% of orthotists working with NHS and private patients would leave the orthotic profession if they could, suggesting a potential retention crisis. The figure was roughly the same among those employed by the NHS and those employed by private companies.

Around 70% of orthotists in the UK work in NHS settings but are employed by private companies. The research found that the leading reason for orthotists wanting to leave the profession was treatment by their employer. Many respondents also reported they did not have enough time with patients during appointments, and that facilities were inadequate. Privately employed orthotists reported that their working conditions were significantly lower than those employed by the NHS.

Orthotic services provide financial value to the NHS. A previous report by the NHS Purchasing and Supply Agency found that the health service could save £4 for every £1 spent on improving orthotics services, because patients who access these services suffer fewer falls and require less pain relief or surgical interventions.

Orthotics services provide treatment options for people with a wide range of conditions and orthotists work closely with a number of clinical specialties within the NHS including diabetes care, elderly medicine, neurology, orthopaedics, paediatrics, stroke and trauma teams.

Dr Nebil Achour, co-author of the paper and Associate Professor in Disaster Mitigation at Anglia Ruskin University (ARU), said: “This study highlights the substantial challenges facing the orthotic profession in terms of staff satisfaction and retention. The perception among orthotists that they were treated poorly by their employer appears to be the catalyst for a significant number wishing to leave not just their job but the profession overall. This is a vulnerability in our healthcare sector and needs to be addressed urgently.

“A resilient healthcare sector requires all professions and capabilities to be ready to respond effectively during times of adversities.”

Lead author Katie Prosser, who carried out the research while studying for a Masters Degree in Healthcare Management at ARU, said: “These are concerning results with clear and considerable implications for the future of the orthotic workforce, as well as patients requiring their services. Usually if people are dissatisfied with an NHS post they can look to move into private roles. However, in this profession it appears there is little to be gained in terms of job satisfaction or conditions by doing this, which may lead orthotists to want to do something else entirely.”

The peer-reviewed study is published today in the British Journal of Healthcare Management.

JOURNAL

British Journal of Healthcare Management

DOI

10.12968/bjhc.2021.0081 

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Job satisfaction among NHS and private orthotists: a cross-sectional comparative study

ARTICLE PUBLICATION DATE

9-Jan-2023

Is ‘fear’ driving bias in environmental scholarship?

Peer-Reviewed Publication

YALE UNIVERSITY

The term “landscapes of fear” is well established in the field of ecology. Traditionally, it refers to  how the risk of predation affects animal behavior and, in turn, the ecosystems in which they live. Researchers including Oswald Schmitz, Oastler Professor of Population and Community Ecology at YSE, have ventured deep into this concept to understand how fear affects key ecosystem functions like decomposition and carbon cycling.

But when the lens is turned, what role does “fear” play on a researcher.

A recent paper published in BioScience, led by Yale School of the Environment PhD student Gabriel Gadsden, proposes a new take on the concept: “social-ecological landscapes of fear.” The hypothesis, Gadsden explains, is that certain places hold legacies derived from historical events that create “identity bias,”  leading to unsatisfactory lines of inquiry that affect the success of conservation goals.

“Much like animals will not use certain spaces because of risk of predation or reduction of resource uses, people are afraid of certain landscapes, and  our discipline is lacking a bit because of it.”” says Gadsden, who works in the Applied Wildlife Ecology (AWE) lab of Dr. Nyeema Harris, Knobloch Family Associate Professor of Wildlife and Land Conservation and senior author of the paper. 

The authors argue that few landscapes are entirely associated with positive identities. The recent history of globalization, modernization, and colonization — and the racism, exploitation, and displacement there within — underscores the necessity to understand how our ecological and evolutionary processes have been impacted, they say.

"As we explore locations for new projects, we are forced to grabble with the identity of that place beyond its biodiversity. We need to know the political, economic, and historic context to design inclusive, culturally sensitive, and impactful science," Harris says.

As an example, the authors explain how housing discrimination has impacted environmental processes in urban environments, creating inequities within cities that are evident today. But Gadsden admits that using case studies to explain the concept would paint an incomplete picture.

“Place-based bias and research is not a three-part case study," he says. "It is historic and present, multi-scale, and includes multiple historical traumas of different peoples, from marine ecosystems to the tropics to the American West.

“There are often powers beyond our control that choose what we think of these spaces. It then affects our scholarship. I know I’m certainly not immune to it. But there are ways we can overcome our biases," Gadsden says.

To do so, the authors provide several recommendations. First, researchers need to recognize negative histories, from further education on the historical context to engaging in land acknowledgments. Then, researchers should include community perspectives when engaging in conservation work.

“In the context of geographies chosen for scientific inquiry, any semblance of fear that prohibits research must be acknowledged and then dissolved. For example, persistent cases of police violence that disproportionately result in the killing of Black people, be it in Minneapolis, Ferguson, or New York City, could result in less research in these locations by Black scholars because of the trauma held there. We recognize building effective partnerships as one strategy to combat fears researchers may have working in a place," Harris says.

The authors also suggest “co-creation” — collaboration with local environmental justice and political ecology scholars.

“I hope these ideas broaden the scope of science into geographic spaces that have not been historically investigated and, in areas that have been investigated, there are some retroactive questions about what may have been missed,” Gadsden says. “I don’t think we can just take a  ‘business as usual’ approach to Western science and call it a day anymore. We need to be better, more intentional researchers.”

Gadsden says that Harris and the other researchers in her lab have already begun infusing these ideas into their work. “It challenges all of us and checks our biases. It’s providing a thought-provoking framework that has been very beneficial,” he says.
 

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JOURNAL

BioScience

DOI

10.1093/biosci/biac095 

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Place-based bias in environmental scholarship derived from social–ecological landscapes of fear

 

NASA's retired Compton mission reveals superheavy neutron stars

Peer-Reviewed Publication

NASA/GODDARD SPACE FLIGHT CENTER

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IMAGE: ASTRONAUTS IMAGED THE COMPTON GAMMA RAY OBSERVATORY DURING ITS DEPLOYMENT FROM SPACE SHUTTLE ATLANTIS IN APRIL 1991. view more 

CREDIT: NASA/STS-37 CREW

Astronomers studying archival observations of powerful explosions called short gamma-ray bursts (GRBs) have detected light patterns indicating the brief existence of a superheavy neutron star shortly before it collapsed into a black hole. This fleeting, massive object likely formed from the collision of two neutron stars.

“We looked for these signals in 700 short GRBs detected with NASA’s Neil Gehrels Swift Observatory, Fermi Gamma-ray Space Telescope, and the Compton Gamma Ray Observatory,” explained Cecilia Chirenti, a researcher at the University of Maryland, College Park (UMCP) and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings at the 241st meeting of the American Astronomical Society in Seattle. “We found these gamma-ray patterns in two bursts observed by Compton in the early 1990s.”

A paper describing the results, led by Chirenti, was published Monday, Jan. 9, in the scientific journal Nature.

A neutron star forms when the core of a massive star runs out of fuel and collapses. This produces a shock wave that blows away the rest of the star in a supernova explosion. Neutron stars typically pack more mass than our Sun into a ball about the size of a city, but above a certain mass, they must collapse into black holes.

Both the Compton data and computer simulations revealed mega neutron stars tipping the scales by 20% more than the most massive, precisely measured neutron star known – dubbed J0740+6620 – which weighs in at nearly 2.1 times the Sun’s mass. Superheavy neutron stars also have nearly twice the size of a typical neutron star, or about twice the length of Manhattan Island.

The mega neutron stars spin nearly 78,000 times a minute – almost twice the speed of J1748–2446ad, the fastest pulsar on record. This rapid rotation briefly supports the objects against further collapse, allowing them to exist for just a few tenths of a second, after which they proceed to form a black hole faster than the blink of an eye.

“We know that short GRBs form when orbiting neutron stars crash together, and we know they eventually collapse into a black hole, but the precise sequence of events is not well understood,” said Cole Miller, a professor of astronomy at UMCP and a co-author of the paper. “At some point, the nascent black hole erupts with a jet of fast-moving particles that emits an intense flash of gamma rays, the highest-energy form of light, and we want to learn more about how that develops.”

Short GRBs typically shine for less than two seconds yet unleash energy comparable to what’s released by all the stars in our galaxy over one year. They can be detected more than a billion light-years away. Merging neutron stars also produce gravitational waves, ripples in space-time that can be detected by a growing number of ground-based observatories.

Computer simulations of these mergers show that gravitational waves exhibit a sudden jump in frequency – exceeding 1,000 hertz – as the neutron stars coalesce. These signals are too fast and faint for existing gravitational wave observatories to detect. But Chirenti and her team reasoned that similar signals could appear in the gamma-ray emission from short GRBs.

Astronomers call these signals quasiperiodic oscillations, or QPOs for short. Unlike, say, the steady ringing of a tuning fork, QPOs can be composed of several close frequencies that vary or dissipate over time. Both the gamma-ray and gravitational wave QPOs originate in the maelstrom of swirling matter as the two neutron stars coalesce.

While no gamma-ray QPOs materialized in the Swift and Fermi bursts, two short GRBs recorded by Compton’s Burst And Transient Source Experiment (BATSE) on July 11, 1991, and Nov. 1, 1993, fit the bill.

The larger area of the BATSE instrument gave it the upper hand in finding these faint patterns – the tell-tale flickering that revealed the presence of mega neutron stars. The team rates the combined odds of these signals occurring by chance alone at less than 1 in 3 million.

“These results are very important as they set the stage for future measurements of hypermassive neutron stars by gravitational wave observatories,” said Chryssa Kouveliotou, chair of the physics department at George Washington University in Washington, who was not involved in the work.

By the 2030s, gravitational wave detectors will be sensitive to kilohertz frequencies, providing new insights into the short lives of supersized neutron stars. Until then, sensitive gamma-ray observations and computer simulations remain the only available tools for exploring them. 

Compton’s BATSE instrument was developed at NASA's Marshall Space Flight Center in Huntsville, Alabama, and provided the first compelling evidence that gamma-ray bursts occurred far beyond our galaxy. After operating for almost nine years, the Compton Gamma Ray Observatory was deorbited on June 4, 2000, and destroyed as it entered Earth’s atmosphere.

Goddard manages both the Swift and Fermi missions.

 Neutron star merger simulation [VIDEO] | EurekAlert! Science News Releases

 

JOURNAL

Nature

DOI

10.1038/s41586-022-05497-0 

ARTICLE TITLE

Kilohertz quasiperiodic oscillations in short gamma-ray bursts

ARTICLE PUBLICATION DATE

9-Jan-2023

Cat locomotion could unlock better human spinal cord injury treatment

Peer-Reviewed Publication

GEORGIA INSTITUTE OF TECHNOLOGY

 

IMAGE: MODEL view more 

CREDIT: GEORGIA TECH

Cats always land on their feet, but what makes them so agile? Their unique sense of balance has more in common with humans than it may appear. Researchers at the Georgia Institute of Technology are studying cat locomotion to better understand how the spinal cord works to help humans with partial spinal cord damage walk and maintain balance.

Using a mix of experimental studies and computational models, the researchers show that somatosensory feedback, or neural signals from specialized sensors throughout a cat’s body, help inform the spinal cord about the ongoing movement and coordinate the four limbs to keep cats from falling when they encounter obstacles. Research suggests that with those motion-related sensory signals the animal can walk even if the connection between the spinal cord and the brain is partially fractured.  

Understanding the mechanisms of this type of balance control is particularly relevant to older people who often have balance issues and can injure themselves in falls. Eventually, the researchers hope this could bring new understanding to somatosensory feedback’s role in balance control. It could also lead to progress in spinal cord injury treatment because the research suggests activation of somatosensory neurons can improve spinal neural networks’ function below the site of spinal cord damage.

“We have been interested in the mechanisms that make it possible to reactivate injured networks in the spinal cord,” said School of Biological Sciences Professor Boris Prilutsky. “We know from previous studies that somatosensory feedback from moving legs helps activate spinal networks that control locomotion, enabling stable movement.”

The researchers presented their findings in “Sensory Perturbations From Hindlimb Cutaneous Afferents Generate Coordinated Functional Responses in All Four Limbs During Locomotion in Intact Cats” in the journal eNeuro.

Coordinated Cats

Although genetically modified mouse models have recently become dominant in neural control of locomotion research, the cat model offers an important advantage. When they move, mice remain crouched, meaning they are less likely to have balance problems even if somatosensory feedback fails. Humans and cats, on the other hand, cannot maintain balance or even move if they lose sensory information about limb motion. This suggests that larger species, like cats and humans, might have a different organization of spinal neural network controlling locomotion compared to rodents.

Georgia Tech partnered with researchers at the University of Sherbrooke in Canada and Drexel University in Philadelphia to better understand how signals from sensory neurons coordinate movements of the four legs. The Sherbrooke lab trained cats to walk on a treadmill at a pace consistent with human gait and then used electrodes to stimulate their sensory nerve.

The researchers focused on the sensory nerve that transmits touch sensation from the top of the foot to the spinal cord. By electrically stimulating this nerve, researchers mimicked hitting an obstacle and saw how the cats stumbled and corrected their movement in response. Stimulations were applied in four periods of the walking cycle: mid-stance, stance-to-swing transition, mid-swing, and swing-to-stance transition. From this, they learned that mid-swing and the stance-to-swing transition were the most significant periods because the stimulation increased activity in muscles that flex the knee and hip joints, joint flexion and toe height, step length, and step duration of the stimulated limb.

“In order to maintain balance, the animal must coordinate movement of the other three limbs, otherwise it would fall,” Prilutsky said. “We found that stimulation of this nerve during the swing phase increases the duration of the stance phase of the other limbs and improves stability.”

In effect, when the cat stumbles during the swing phase, the sensation triggers spinal reflexes that ensure the three other limbs stay on the ground and keep the cat upright and balanced, while the swing limb steps over the obstacle.

Computational Cats

With these Canadian lab experiments, the researchers at Georgia Tech and Drexel University are using observations to develop a computational model of the cat’s musculoskeletal and spinal neural control systems. The data gathered are used to compute somatosensory signals related to length, velocity, and produced force of muscles, as well as pressure on the skin in all limbs. This information forms motion sensations in the animal’s spinal cord and contributes to interlimb coordination by the spinal neuronal networks.

“To help treat any disease, we need to understand how the intact system works,” Prilutsky said. “That was one reason why this study was performed, so we could understand how the spinal networks coordinate limb movements and develop a realistic computational model of spinal control of locomotion. This will help us know better how the spinal cord controls locomotion.”

CITATION: Merlet AN, Jéhannin P, Mari S, Lecomte CG, Audet J, Harnie J, Rybak IA, Prilutsky BI, Frigon A (2022) Sensory Perturbations from Hindlimb Cutaneous Afferents Generate Coordinated Functional Responses in All Four Limbs during Locomotion in Intact Cats. eNeuro 9: 0178-22.

 

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The Georgia Institute of Technology, or Georgia Tech, is one of the top public research universities in the U.S., developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its more than 46,000 students, representing 50 states and more than 150 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.

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JOURNAL

eNeuro

DOI

10.1523/ENEURO.0178-22.2022 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Sensory perturbations from hindlimb cutaneous afferents generate coordinated functional responses in all four limbs during locomotion in intact cats