The Economist - USA (2022-02-12)

The Economist February 12th 2022 Science & technology 71

weretaken from theyoungest fully ex­

pandedleavesoneveryplantintheexperi­

mentandstudied.

Noneoftheplantsexposedtothetraffic

noisedidwell.Analysisoftheirleavesre­

vealedthatallofthemweresuffering.The

chemicalcompoundshydrogenperoxide

and malondialdehyde are indicators of

stressinplantsandbothwerefoundat

muchhigherlevelsinthespecimensex­

posedtothetrafficnoise.Mostnotably,

malondialdehydelevelsinthesageplants

exposedtonoiseweredoublewhatthey

wereinthosegrowninsilenceandhydro­

gen­peroxidelevelswerethreetimeshigh­

er in French marigolds grown withthe

noisethanthosegrowninsilence.

Thesecompoundswerenotalone.The

teamfoundthata rangeofhormonesnor­

mallyassociatedwithhealthygrowthand

developmentinplantswerepresentatsig­

nificantlyreducedlevelsintheplantsex­

posedtothenoise.Twostresshormones,

jasmonicacidandabscisicacid,whichare

normallyproducedtofendoffinsectat­

tacksanddealwithsaltysoilorverycold

temperatures, were elevated. Even the

weight ofthefreshly clippedleavesdif­

fered—clippings fromplants exposed to

noiseconsistentlyweighedlessthanclip­

pingsfromplantsgrowninsilence.

DrGhotbi­Ravandi’sresultswerepub­

lished in the journal Basic and Applied

Ecology. Hisfindings makeitclear that,

thoughplantslackears,thevibrationsgen­

eratedbythenoiseoftrafficstillbothers

themenoughto triggerpotentstressre­

sponses that are not much different to

those that would be found in plants

exposedtodrought,highsalinityorheavy

metalsintheirsoil.

Thenextquestioniswhetherallnoise

pollutionaffectsallspeciesinthesame

way.Thenaturalworldisbynomeanssi­

lent.Alpinemeadowsareexposedtono

shortageofcacophonousgales.Fernsgrow

alongtheedgesofturbulentpoolsfedby

thunderous waterfalls. Whether some

plantspecieshaveevolvedcopingmecha­

nisms,whichmightonedaybecollected

andtransferredintourban­dwellingspe­

cies,isa mysteryworthexploring.n

Neurology

Standing ovation

F

ouryearsagoMichelRoccatiwasin­

volved in a motorcycle accident. He suf­

fered  what  neurologists  call  a  “complete”

spinal­cord  injury—he  lost  all  sensation

below  the  site  of  the  damage  to  his  spine

and  he  could  no  longer  move  his  legs.  In

December  last  year,  however,  the  young

Italian stood up on the streets of Lausanne,

Switzerland, and took a short walk.

Mr Roccati’s remarkable steps, support­

ed  by  a  wheeled  walking  frame,  were  the

conclusion of more than a decade of work

by  Grégoire  Courtine,  a  neuroscientist  at

the Federal Institute of Technology in Lau­

sanne, and Jocelyne Bloch, a neurosurgeon

at Lausanne University Hospital. 

The  scientists  had  fitted  Mr  Roccati

with a device that stimulated nerves in his

back  that  once  controlled  muscles  in  his

lower  body  and  legs,  but  which  had  lain

dormant since his accident.

Even  after  a  severe  spinal  injury,  the

nerves that control activities such as walk­

ing  often  remain  intact  below  any  dam­

aged tissue. In people with paralysis, how­

ever,  the  damaged  tissue  interrupts  or

weakens  any  electrical  signals  coming

from the brain. 

Dr  Courtine  and  Dr  Bloch  developed  a

wafer­thin  device  with  electrodes  that

couldtargetthedormantnerves. Once im­

planted  into  Mr  Roccati’s  back,  the  device

sent in pulses of electricity that mimicked

those normally present in the nerves of an

uninjured person as they walk. 

By  doing  this,  the  device  acted  like  an

amplifier for any electrical signals coming

from  Mr  Roccati’s  brain.  Those  signals

would  normally  be  blocked  by  his  dam­

aged spinal tissue and be incapable of acti­

vating  the  nerves  in  his  lower  back.  But

with  the  stimulation  device  in  place,  Mr

Roccati  was  able  to  voluntarily  control

those once­dormant nerves, allowing him

to move his legs and walk.

Mr  Roccati  was  one  of  three  paralysed

volunteers who took part in a small clinical

trial  of  the  device,  details  of  which  were

published this week in the journal Nature

Medicine.  The  device  worked  well  enough

that all three users in the trial were able to

stand  up  and  take  a  few  steps  almost  im­

mediately  after  they  had  recovered  from

the surgery to have it implanted.

This  was  a  marked  improvement  on

previous  implementations  of  this  kind  of

technology, in which scientists had repur­

posed  nerve  implants  normally  used  to

treat  chronic  pain.  In  the  few  instances

where  those  experiments  had  been  suc­

cessful, it had taken many months of train­

ing for patients to learn to walk again.

Dr Courtine’s and Dr Bloch’s new device

can  be  configured  to  fire  its  electrical  im­

pulses in many different patterns, each of

which  corresponds  to  a  different  activity.

Patients  in  the  trial  were  not  only  able  to

stand  and  walk,  but  eventually  also  to

swim and cycle. 

The new device will need approval from

medical regulators before it can be used in

clinics.  Its  inventors  set  up  a  company

called  NeuroRestore,  which  is  working

with Onward Medical, a Dutch company, to

commercialise their new device. 

The impact of the device on the lives of

those in the small Swiss trial, however, has

already  been  dramatic.  Mr  Roccati  high­

lights  the  little  things—walking  up  stairs,

for example, or standing in the shower. At a

bar,  he  can  stand  up  to  chat  with  friends.

After training, he is nowalsoable to walk

around for two hours everyday.“With the

walker,” he says. “I am free.”n

Spinal implants allow paralysed people to walk, swim and cycle again

Michel Roccati (left), walks with David Mzee (right), a fellow spinal-implant patient