28 | New Scientist | 26 September 2020
Book
Livewired: The inside story
of the ever-changing brain
David Eagleman
Canongate BooksIMAGINE if your 6-year-old
son needed surgery to remove
a staggering half of his brain. That
was what faced Matthew, a boy
with a rare condition triggering
many epileptic seizures a day and
that could only be treated with
this drastic surgery. When he woke
up afterwards, he was incontinent
and couldn’t walk or speak.
Yet with daily physical and
language therapy, Matthew
regained these abilities. In three
months, he was almost back to
normal, minus the seizures.
Now an adult, brain scans show
half of Matthew’s skull as a
black void, yet the only visible
effects are his slight limp and a
little clumsiness in his right hand.
How could someone lose half
of their brain and recover almost
all of their functioning in three
months? For neuroscientist David
Eagleman at Stanford University
in California, this demonstrates
one of the brain’s most remarkable
qualities: neuroplasticity, or the
ability to remake itself in response
to changing circumstances.
In Livewired, Eagleman explains
why this ability is so fundamental
to who we are that James Watson
and Francis Crick’s claim to have
discovered the “secret of life” with
their work on DNA is only half of
the story. The rest of what makes
you who you are is “every bit
of experience you have with the
world: the textures and tastes, the
caresses and car accidents, the
languages and love stories... all of
which sculpt the vast, microscopic
tapestry of your brain cells and
their connections,” he writes.Obviously, since we can’t
dissect the brains of living people,
it is very hard to observe those
transformations at the molecular
and cellular level. Yet we can
clearly see their effects on
behaviour and abilities. It is why
we are able to learn new skills,
even in later life, and why some
people who are blind can learn to
echolocate in a similar way to bats.
Brain scans show that in people
who lose their sight, the part of the
brain that usually receives signals
from the eyes instead starts
processing input from their ears
and their sense of touch. This
starts to happen even in people
who are blindfolded for a few days.
Eagleman and his team are
exploiting this flexibility by
making devices that let people
receive sensory information in
new ways. They have built special
vests and wristbands for people
who are deaf. These capture sounds
and translate them into vibrations
through pads next to the skin.
Eagleman envisages that, one day,
such devices may not only replace
lost senses, but also create new
ones. For instance, a politician
giving a speech could use a vest to
monitor its reception on Twitter
and dial it up or down accordingly.
The nervous system seems to
accept such tinkering surprisingly
quickly. Eagleman has a good
example: can you guess how
long it takes people to get used
to manipulating three arms in
virtual reality, with the third
sprouting from the middle of
their chest? Just 3 minutes.
Yet neuroplasticity has its
limits. As we get older, our brains
become less flexible and more
stable. Older people can still learn
a language or musical instrument,
but the operation experienced by
Matthew would be disastrous – it
isn’t generally recommended for
children aged 8 or older.In extreme cases, this brain
resculpting is visible at the
anatomical level through
post-mortems or scans.
Professional musicians
develop a small bulge on a ridge
of their motor cortex – a part
of the brain that controls
movement – revealing the
effects of thousands of hours
moving their fingers in complex
choreographies. It is reminiscent
of the way a large bicep may
reflect the hours spent at the gym.
Research on animals shows
that such a cortical bulge arises
from rewiring at multiple levels.
Not only is there the growth
of new synapses (connections
between brain cells) but there
are also changes to the molecular
machinery of those synapses.
Neurons can sprout more
branches, and sometimes
whole new neurons can form.Views Culture
Our brains can remake
themselves to adapt to
changing circumstancesANDR
IY^
ONUF
RIYENKO
/GETT
Y^ IAMGESHow our brains make us
Livewired reveals the intriguing reasons why a 6-year-old can thrive with half a
brain and why some people who are blind can echolocate, finds Clare Wilson“ DNA is only half of
what makes you who
you are – the rest is all
the experience you
have with the world”