28 March 2020 | New Scientist | 15PEOPLE with Parkinson’s
disease are getting brain
implants that can automatically
detect and reduce harmful
nerve cell activity. Researchers
are testing the devices to
see if they can improve the
movement difficulties that
people with the condition have,
while reducing the side effects
the conventional form of this
invasive treatment can lead to.
Parkinson’s disease causes
worsening tremors and
difficulties with movement,
especially when initiating
actions. Medication can help,
but as symptoms progress,
some people undergo a more
invasive treatment, called
deep brain stimulation (DBS).
This works by placing wires
into the skull that deliver a
current to dampen down the
activity in clusters of nerve
cells in the centre of the brain.
Unfortunately, it can cause side
effects such as speech difficulties
and jerky movements.
It may be possible to
minimise these side effects
by delivering stimulation only
when it is needed, known asresponsive stimulation. A
similar kind of brain implant
is already used in a few people
with severe epilepsy that is
unresponsive to medicines
or surgery, to reduce the
excessive nerve cell activity
that causes seizures. But in
people with Parkinson’s, it is
less clear what kind of brain
activity causes the different
symptoms and side effects.
One area of interest is the
nerve cell clusters deep in the
brain targeted by the implants.
In most people, these centres
sometimes fire in synchronous
patterns called beta waves
to signal that we should
continue our present behaviour.“It promotes the status quo,”
says Peter Brown at the
University of Oxford.
In Parkinson’s, there is an
excess of beta waves, and this
could explain why people with
the condition sometimes movemore slowly than they want
to and have difficulties
initiating new movements.
So Brown and his colleagues
are trying to stimulate the
nerve cell clusters only when
beta waves are detected.
The team tried the technique
in 13 people with Parkinson’s
who had a particular problem
with moving too slowly, while
they were having surgery
under a local anaesthetic
to replace the battery of their
existing DBS implant. Brown’s
team found that the responsive
stimulation caused less speech
impairment than conventional
constant stimulation, and
it was about as effective at
combating slow movements
(bioRxiv, doi.org/dp5f).
However, the approach might
not be suitable for everyone.
Responsive stimulation led to
the recurrence of the tremor
in two patients. Tremor may be
caused by problems in different
nerve clusters, says Brown.
Tim Denison at the University
of Oxford, who wasn’t involved
in the study, is trying to develop
another kind of responsive
DBS that targets the approach’s
other main side effect:
involuntary jerky movements.
By introducing a second wire
on the surface of the brain,
his team has found that these
movements are accompanied
by another kind of brain wave,
known as gamma waves, in an
area called the motor cortex.
He hopes that people could
have their DBS activity turned
down automatically when
gamma waves are detected.
“This is where the field is
heading,” says Denison. ❚AN ARCHAEOLOGICAL excavation
in southern Spain has uncovered the
2000-year-old remains of a lapdog
that may have been born thousands
of kilometres away. Its discovery
hints at a long-distance trade in
lapdogs across the Roman world.
Rafael Martinez Sánchez at the
University of Granada, Spain, and his
colleagues found a lapdog skeleton
buried in a Roman cemetery in
southern Spain. It was about
22.5 centimetres tall at the shoulder
and had a small skull with large
eyes, rather like a modern Pekinese.
Wear on the dog’s teeth shows
that it was an adult that was
probably between 2 and 4 years
old when it died. Fetal bones found
inside the skeleton suggest that
the lapdog was a female and was
pregnant when she died.
An analysis of the lapdog’s bones
and teeth revealed that she may not
have been local. The carbon and
oxygen isotopes in bones provide
information on the environment
an animal’s food and water came
from, and the lapdog’s bones
suggest she grew up drinking
water far away from the Atlantic.
This means she probably
wasn’t born in southern Spain
but somewhere to the east, says
Martinez Sánchez, perhaps Italy
or the eastern Mediterranean.
Two larger dogs buried in the same
cemetery lacked this chemical
signal and seem to have been born
and raised locally (Archaeological
and Anthropological Sciences,
doi.org/dp5g).
“This animal had a life
significantly different from that
of the other animals found in the
necropolis,” says Martinez Sánchez.
Its exotic origins might even hint at
long-distance trade of small dogs
in the Roman world, the researchers
say. But this didn’t save her from a
grizzly end. A fractured neck bone
indicates she may have been killed
following her owner’s death. ❚Standard implants
deliver constant
electrical stimulationAnimals NeuroscienceColin Barras Clare WilsonVINCE
NT
MONCORGE
/LOOK
ATSCIENCE
S/SPLYBrain implant kicks in as
Parkinson’s gets worse
Well-travelled
lapdog hints at
Roman pet trade
13
The number of people in the
experimental brain implant trial