Medical Design Briefs - October 2024 - 56

Flexible Tentacle Electrodes Precisely Record Brain Activity
ETH Zurich, Zurich, Switzerland
N
eurostimulators, also known as brain
pacemakers, send electrical impulses
to specific areas of the brain via special
electrodes. It is estimated that some
200,000 people worldwide are now benefiting
from this technology, including
those who suffer from Parkinson's disease
or from pathological muscle spasms.
According to Mehmet Fatih Yanik, professor
of neurotechnology at ETH Zurich,
further research will greatly expand
the potential applications: instead of using
them exclusively to stimulate the
brain, the electrodes can also be used to
precisely record brain activity and analyze
it for anomalies associated with neurological
or psychiatric disorders. In a
second step, it would be conceivable in
future to treat these anomalies and disorders
using electrical impulses.
To this end, Yanik and his team have
now developed a new type of electrode
that enables more detailed and more
precise recordings of brain activity over
an extended period of time. These electrodes
are made of bundles of extremely
fine and flexible fibers of electrically conductive
gold encapsulated in a polymer.
Thanks to a process developed by the
ETH Zurich researchers, these bundles
can be inserted into the brain very
slowly, which is why they do not cause
any detectable damage to brain tissue.
This sets the new electrodes apart
from rival technologies. Of these, perhaps
the best known in the public
sphere is the one from Neuralink, an
Elon Musk company. In all such systems,
including Neuralink's, the electrodes
are considerably wider. " The
wider the probe, even if it is flexible,
the greater the risk of damage to brain
tissue, " Yanik explains. " Our electrodes
are so fine that they can be
threaded past the long processes that
extend from the nerve cells in the
brain. They are only around as thick as
the nerve-cell processes themselves. "
The research team tested the new
electrodes on the brains of rats using
four bundles, each made up of 64 fibers.
In principle, as Yanik explains,
up to several hundred electrode fibers
could be used to investigate the
activity of an even greater number of
56
brain cells. In the study, the electrodes
were connected to a small recording device
attached to the head of each rat,
thereby enabling them to move freely.
n No Influence on Brain Activity
In the experiments, the research team
was able to confirm that the probes are
biocompatible and that they do not influence
brain function. Because the electrodes
are very close to the nerve cells,
the signal quality is very good compared
to other methods.
At the same time, the probes are suitable
for long-term monitoring activities,
with researchers recording signals from
the same cells in the brains of animals
for the entire duration of a ten-month
experiment. Examinations showed that
no brain-tissue damage occurred during
this time. A further advantage is that the
bundles can branch out in different directions,
meaning that they can reach
multiple brain areas.
n Human Testing to Begin Soon
In the study, the researcher used the
new electrodes to track and analyze nervecell
activity in various areas of the brains of
rats over a period of several months. They
were able to determine that nerve cells in
different regions were " co-activated. " Scientists
believe that this large-scale, synchronous
interaction of brain cells plays a
key role in the processing of complex information
and memory formation. " The
technology is of high interest for basic research
that investigates these functions
and their impairments in neurological
and psychiatric disorders, " Yanik says.
The group has teamed up with fellow researchers
at the University College London
in order to test diagnostic use of the new
electrodes in the human brain. Specifically,
the project involves epilepsy sufferers who
do not respond to drug therapy. In such
cases, neurosurgeons may remove a small
part of the brain where the seizures originate.
The idea is to use the group's method
to precisely localize the affected area of the
brain prior to tissue removal.
n Brain-Machine Interfaces
Rigid
silicon
probe
Flexible
planar
shank probe
(Neuralink)
Neural
mesh
Ultra-flexible
tentacle
electrodes
The tentacle electrodes (right) shown alongside three current
technologies using thicker electrodes or an electrode mesh.
(Credit: Yasar TB et al. Nature Communications 2024, modified)
www.medicaldesignbriefs.com
There are also plans to use the new
electrodes to stimulate brain cells in humans.
" This could aid the development
of more effective therapies for people
with neurological and psychiatric disorders, "
says Yanik. In disorders such as depression,
schizophrenia, or OCD, there
are often impairments in specific regions
of the brain, which leads to
problems in evaluation of information
and decision making. Using the new
electrodes, it might be possible to detect
the pathological signals generated
by the neural networks in the brain in
advance, and then stimulate the brain
in a way that would alleviate such disorders.
Yanik also thinks that this technology
may give rise to brain-machine
interfaces for people with brain injuries.
In such cases, the electrodes
might be used to read their intentions
and thereby, for example, to control
prosthetics or a voice-output system.
This research was funded in part by
a Consolidator Grant from the European
Research Council (ERC) awarded
to Mehmet Fatih Yanik in 2018 and
the Swiss National Science Foundation's
Sinergia programme.
For more information,
contact
Mehmet Fatih Yanik at yanik@ethz.ch
or visit https://ethz.ch.
Medical Design Briefs, October 2024
https://ethz.ch/ https://www.medicaldesignbriefs.com
Medical Design Briefs - October 2024

Table of Contents for the Digital Edition of Medical Design Briefs - October 2024
