New Scientist - USA (2019-06-22)

(Antfer) #1
22 June 2019 | New Scientist | 37

Think about thinking, and it doesn’t take
long for your mind to go down a rabbit
hole. Thoughts come naturally to us, but
pinning down exactly what they are is
more complicated. Once they were viewed
as immaterial entities, separate from the
biological matter of the brain. Now we know
that our every thought – whether about a
simple object or an abstract idea – is the
result of electrical signals pulsing through
the brain’s network of 86 billion neurons.
“For me, a thought is simply the
transformation of inputs to outputs by
the brain,” says Ethan Solomon at the
University of Pennsylvania.
But if you ask 100 neuroscientists for a
definition, you will get 100 different answers,
says Avgusta Shestyuk at the University of
California, Berkeley. “‘Thinking’ is an umbrella
term that covers multiple different cognitive
processes,” she says. Some thoughts take the
form of pictures, others seem to be comprised
of words, and many take place at the
unconscious level, without us even noticing.
The latest neurological studies let us tune
into the electrical signals that underlie
thinking. They show that even a basic

kilometres of


nerve fibres


850,000


The short answer is yes. People vary in
their intelligence, so how else could we
account for this if not for differences in the
structure or function of the brain? Exactly
what those differences are, however, is a
matter of intense investigation.
The first thing to note is that people with
larger brains really do tend to have higher
IQs, but there is more to this than size (see
“What makes our brain special?”, page 34).
To find out more, we need to zoom into the
white and grey matter that makes up our
brain. The latter is comprised of the main
bodies of neurons, whereas white matter
is made of the fibres down which they send
signals. Rogier Kievit at the MRC Cognition
and Brain Sciences Unit in Cambridge, UK,
and his colleagues have found that the
volume of grey matter in the frontal lobe
(see diagram, right) is connected to fluid
intelligence, which is the ability to solve
novel problems. They also found this
was linked to the amount of white matter
connections between the two halves of
the prefrontal part of the brain.
It isn’t just the amount of tissue that
counts. One of the most striking features
of the mammalian brain is the way it has
deep folds of grey matter on its surface,
giving it a walnut-like appearance. These
increase its surface area, bringing cells
closer together and allowing them to
communicate faster. And sure enough,
the extent of the folding is correlated with
speed of thought and working memory:
smarter people have more-folded brains.
But this still doesn’t tell us where in the
brain intelligence resides. To find this out,
we can turn to one of the most popular
ideas about its location, something called
parieto-frontal integration theory. This
proposes that the biological basis of
intelligence is a network connecting
different brain hotspots.
Clues about these hotspots can be found
in brain-imaging studies. By examining
how parts of the brain became activated
during cognitive tasks, Ulrike Basten at
Goethe University Frankfurt in Germany
and her colleagues identified a network
connecting 20 different areas in the frontal
and parietal regions that were associated
with intelligence. People with more grey
matter or higher neural activity in these
regions were smarter.
It feels like we are getting somewhere,
but that result doesn’t just mean that


smarter people have physically different
brains: they seem to have ones that work
more efficiently too. A brain might have the
right chassis for high performance, says
Emiliano Santarnecchi of Harvard Medical
School, “but it’s not that relevant without
an on-board computer regulating how
power is delivered and when to allocate
resources at any given moment”.
Santarnecchi’s work suggests
that intelligence can be boosted by
magnetic stimulation to increase the
brain’s processing efficiency. He also
emphasises the importance of plasticity,
or the ability to change. Perhaps some
people’s brains are inherently more
plastic, more capable of learning.
This is to say nothing of genetics.
Although we know that hundreds of
genes contribute to intelligence, it
is going to take a long time to discover
the nuances of their impact. But then it
was never going to be a simple matter
to find the location of intelligence, the
richest human trait, in the brain, the most
complex known object in the universe. RH

What happens
when we think?

Are smarter people’s
brains different?

Alpha brainwaves >

Visual cortex

Occipital lobe
Visual processing

Auditory cortex
Hippocampus

Know your brain
The human brain operates using specialised processing units

BOTTOM BRAIN
Classifies and
interprets information

TOP BRAIN
Creates and
monitors plans

Frontal lobe

Prefrontal
cortex

Motor cortex
Problem-solving, complex
thinking, decisions

Planning
complex
behaviour

Planning and
executing movement

Integration of sensory
information, perception

Parietal lobe

Language, hearing,
processing sensory
information into memories
Memory

Temporal lobe

SOURCE: AI IMPACTS
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