22 June 2019 | New Scientist | 39Estimated memory
capacity of the
human brain
[equivalent to that of the
World Wide Web]petabyte
circumstances. Bottom-brained types
think through the details of a plan but are
less likely to initiate complex schemes.
Anderson, however, posits that our
personalities probably arise from the way
various brain systems are connected and
how rich those links are. For instance,
people who are open to new experiences
are more likely to get goosebumps when
they see a beautiful sunset. Brain scans
show that they have more connections
between areas that process sensory
information and regions responsible
for our inner voice.
We can feed this information into
deep-learning machines that can make
accurate predictions about personality
traits based on a person’s brain scan, says
Anderson. “It’s not about anyone using
the left or right side of the brain more,”
he says, “it’s about subtle differences in
connections across the whole brain.”
Helen Thomson
When you rest, it sometimes feels as if your
brain switches off too. It doesn’t. If you are
alive, your neurons are firing. “There is a lot
of processing going on even when you’re not
seemingly doing anything at all,” says Deniz
Vatansever, a cognitive neuroscientist at
Fudan University in China.
It could hardly be any other way. Moment-
to-moment readiness was a matter of life
and death for our ancestors. These days,
most of us don’t have to worry about
leopards leaping from the undergrowth.
But we still need to be alert to dangers andIs your brain
ever off?opportunities, and that requires a brain that
is working constantly.
Back in the 1990s, neuroscientists noticed
that people lying quietly in brain scanners with
their eyes closed showed surprising levels of
brain activity. The researchers soon mapped
the brain regions that are most active during
rest, and this became known as the default
mode network. This shows little activity when
we are engaged in tasks requiring attention,
but fires up when we “switch off ”, allowing our
minds to wander.
Some evidence suggests that the default
mode network is involved in mulling over past
experiences and speculating about the future.
In that sense, it is vital because daydreaming
is considered to be one of the abilities that sets
us apart from other animals. But the default
mode network does more than that. In 2017,
Vatansever and his colleagues demonstrated
that it underlies our ability to do certain things
without paying attention, such as tying our
shoelaces or driving along a familiar route –
our autopilot mode.Shutting down
The brain is a hive of activity during sleep,
too. Once consciousness is lost, it gets to work
on all manner of chores: clearing out toxic
molecules, regulating hormone levels and
conjuring dreams, which are thought to
provide a safe environment to simulate
new behaviours that could help during
waking life. The sleeping brain also files
away experiences for later recall.
Even when someone is in a vegetative state,
unconscious and apparently unresponsive
for a prolonged period, their brain continues
to work at some level. When some people in
this state are asked to imagine themselves
playing tennis, for instance, blood flow
increases in brain regions associated with
motor skills, suggesting that the neurons there
are firing. In one case, a patient seemingly
activated those regions on command in
response to yes-or-no questions.
Only when you die do your neurons
completely shut down. Except even then,
there is a final burst of activity, as Jed Hartings
at the University of Cincinnati in Ohio and his
colleagues recently showed for the first time in
humans. When the heart is no longer pumping
blood to the brain, starving it of oxygen,
neurons draw on energy reserves to continue
firing for up to 3 minutes before they produce
one last burst of electrochemical energy. Only
then is the brain switched off for good.
Daniel Cossins~ 1
SOURCE: ELIFE, DOI.ORG/GDZ74X>