NASA/JOHN HOPKINS APL; UNIVERSITY OF BATH. OPP: GETTY IMAGESDIGEST
20 – COSMOS Issue 86
Researchers successfully create
them on tiny silicon chips.
The authors of a study in Nature
Communicationsexhibit the kind of calm
rationality that makes one believe. They
point out that neuromorphic silicon devices
replicating biological nerve functions have
been proposed before, but problems have
hampered attempts to develop them.
The design of devices such as silicon
neurons, synapses and brain-inspired
networks is not meant to copy the behaviour
of biological cells, they say, but to search for
the organising principles of biology that can
be applied to practical devices.
However, an increasing focus on
implantable bioelectronics to treat chronic
disease is changing this paradigm and
“instilling new urgency in the need for low-
power analogue solid-state devices that
accurately mimic biocircuits”.
The British/Swiss/New Zealand team’s
paper describes a way of making silicon
chips that are smaller than a fingertip
but reproduce the electrical behaviour of
biological neurons. This, they say, could
lead to the development of bionic chips
to repair biological circuits in the nervous
system when functions are damaged or lost
to disease.
They designed microcircuits modelling
ion channels that integrate raw nervous
TECHNOLOGY
Artificial neurons can behave
like real ones
stimuli and respond in a similar way to
biological neurons, then recreated the
activity of individual hippocampal and
respiratory neurons in silicon chips.
In a series of 60 electrical stimulation
protocols, they found that the solid-
state neurons produced nearly identical
electrical responses when compared to
biological neurons.
“We can very accurately estimate
the precise parameters that control any
neurons behaviour with high certainty,”
says Alain Nogaret, from the University of
Bath. “We have created physical models of
the hardware and demonstrated its ability
to successfully mimic the behaviour of real
living neurons.
“Our third breakthrough is the
versatility of our model, which allows
for the inclusion of different types and
functions of a range of complex mammalian
neurons.”
Nogaret and colleagues note that
respiratory neurons, such as those they
have modelled, couple respiratory and
cardiac rhythms and are responsible for
respiratory sinus arrhythmia.
Loss of this coupling through age or
disease is a prognosis for sleep apnoea and
heart failure. They suggest that a device
that adapts biofeedback in the same way as
respiratory neurons may offer a potential
therapy in the future. – IAN CONNELLANFirst results
from close to
the sun
Parker Solar Probe data paint a
complex picture.The first results from NASA’s Parker
Solar Probe reveal that the Sun’s outer
atmosphere is even more complex than
scientists thought.
Launched in 2018, Parker’s mission is
to dive ever closer to the Sun, eventually
getting to just more than six million
kilometres from its surface.
The two encounters to date have not
gotten any closer than 24 million, but
that’s less than half the distance between
the Sun and Mercury, and twice as close
as any prior spacecraft.
One surprise, says Daniel Verscharen,
a space-plasma physicist at University
College, London, who was not part of the
Parker team, is that the Sun’s magnetic
field has frequent “switchbacks” in which,
for a few minutes, it suddenly reverses
direction.
Something similar had been seen
from further away, “but we had no idea
that they would be so strong and would
occur so often”. These reversals cause the
velocity of the solar wind to alternately
increase and decrease and may contribute
to heating the Sun’s corona.
Also interesting, Verscharen says,
is the discovery that the plasma has
turbulent fluctuations or “instabilities”.
Such turbulence is another way in which
energy can be transferred from the
magnetic field to the plasma, thereby
heating it. – RICHARD A LOVETT