38 | New Scientist | 22 June 2019
thought involves a surprising amount of
activity, with different brain areas firing
up and sending information to others, and
certain “hub” regions directing the traffic.
Last year, for example, Shestyuk and her
colleagues recorded the journey of individual
thoughts in the brain by measuring the
electrical signals involved when people
were asked to recall and say a word. The first
areas to show activity were the visual and
auditory cortices, which receive signals from
the eyes and ears. Next, the brain’s command
centre – the prefrontal cortex – kicked in.
The harder the memory task, the more of
the prefrontal cortex that became activated,and the longer it took to respond, reflecting
the time taken for the region to recruit
other brain areas such as networks where
memories are stored. Finally, the motor
cortex revved up to generate a spoken
response. Surprisingly, this happened
before the prefrontal cortex had decided
on a response. “That’s why we sometimes
start speaking before we know what we want
to say,” says Shestyuk.
So, the prefrontal cortex helps orchestrate
thought processes, but the signals involved
also need to be coordinated. That is the job
of brainwaves: ripples of neural activity
oscillating at different frequencies across
the brain. Solomon’s research reveals that
during a memory test, low-frequency
theta waves in the various brain regions
involved become coordinated, and this
synchronisation probably allows information
to be communicated between the regions.
Our new-found ability to eavesdrop
on individual thoughts means that mind-
reading devices are no longer just the stuff
of fiction. Earlier this year, electrodes on
the brain were used to translate brainwaves
into words spoken by a computer. Techniques
like these could help people with locked-in
syndrome – who are conscious but unable
to move – to communicate. All thanks to the
power of thought.
Alison GeorgeChances are you have thought of yourself
as left or right-brained: rational and
logical, or creative and free-spirited.
Appealing as this concept is, it is also
a complete myth.
It is easy to see how the idea was
born. In the 1960s, we discovered that
certain functions occur solely on one
side of the brain. Most people process
language in the left hemisphere, whereas
our emotions are dealt with in the right.
It was soon said that our left hemisphere
held a monopoly over the virtues of logic,
reason and language. The right side of
the brain was responsible for driving our
emotions, musicality and impulsiveness.
From this came the popular maxim that
whichever side of your brain dominated,
determined your personality.
The truth is more nuanced. For
instance, although your left hemisphere
produces complex speech, the right
allows you to understand the emotional
and metaphorical content of those
words – it gives you some linguistic
finesse. Creative thought, on the other
hand, activates a widespread network
of cells that favour neither hemisphere.
Moreover, there is no evidence that
one side of the brain dominates. Jeffrey
Anderson at the University of Utah
has scanned the brains of more than
1000 people while they performed
various tasks and showed that none
revealed a dominance for using one
side of their brain over the other.Top to bottom
Other ideas abound. The “theory of
cognitive modes”, developed by Stephen
Kosslyn at Harvard University, holds that
our cognitive style is determined by
whether we are top or bottom-brained
(see diagram, page 37). The top regions
of our brain are involved in formulating
and carrying out plans, and revising them
when they go wrong. Lower regions are
largely concerned with processing inputs
from the senses, classifying objects and
events, and giving them meaning.
Everyone uses their whole brain all of
the time, says Kosslyn, but each of us to
some extent relies more on top or bottom
systems, and this affects our behaviour. A
top-brain dominated person, for instance,
will be more of a creative go-getter, but
sometimes ineffective because they
don’t update plans based on currentAre you thinking
what I’m thinking?“ Mind-reading
devices are
no longer
the stuff
of science
fiction”
Theta brainwavesAre you really left
or right-brained?DORISRUDDDESIGNS
/GETT
Y