Mind Hacks™: Tips & Tools for Using Your Brain (4 page)

Positron emission tomography
(PET) is more invasive than any of the
other imaging techniques. It requires getting a radioactive chemical into the bloodstream
(by injection) and watching for where in the brain the radioactivity ends up — the “positron
emission” of the name. The level of radioactivity is not dangerous, but this technique
should not be used on the same person on a regular basis.

When neurons fire to send a signal to other neurons, they metabolize more energy. A few
seconds later, fresh blood carrying more oxygen and glucose is carried to the region. Using
a radioactive isotope of water, the amount of blood flow to each brain location can be
monitored, and the active areas of the brain that require a lot of energy and therefore
blood flow can be deduced.

Functional magnetic resonance imaging
(fMRI) is the king of brain
imaging. Magnetic resonance imaging is noninvasive and has no known side effects — except, for
some, claustrophobia. Having an MRI scan requires you to lie inside a large electromagnet in
order to be exposed to the high magnetic field necessary. It’s a bit like being slid inside
a large white coffin. It gets pretty noisy too.

The magnetic field pushes the hydrogen atoms in your brain into a state in which they
all “line up” and spin at the same frequency. A radio frequency pulse is applied at this
exact frequency, making the molecules “resonate” and then emit radio waves as they lose
energy and return to “normal.” The signal emitted depends on what type of tissue the
molecule is in. By recording these signals, a 3D map of the anatomy of the brain is built
up.

MRI isn’t a new technology (it’s been possible since the ’70s), but it’s been applied to
psychology with BOLD functional MRI (abbreviated to fMRI) only as recently as 1992. To
obtain functional images of the brain, BOLD (blood oxygen level dependent) fMRI utilizes the
fact that deoxygenated blood is magnetic (because of the iron in hemoglobin) and therefore
makes the MRI image darker. When neurons become active, fresh blood washes away the
deoxygenated blood in the precise regions of the brain that have been more active than
usual.

While structural MRI can take a long time, fMRI can take a snapshot of activity over the
whole brain every couple of seconds, and the resolution is still higher than with PET
[
Positron Emission Tomography: Measuring Activity Indirectly with PET
]
. It can view activity in volumes of the brain only 2 mm across and build a
whole map of the brain from that. For a particular experiment, a series of fMRI snapshots
will be animated over a single high-resolution MRI scan, and experimenters can see in
exactly which brain areas activity is taking place.

Much of the cognitive neuroscience research done now uses fMRI. It’s a method that is
still developing and improving, but already producing great results.

Transcranial magnetic stimulation
(TMS) isn’t an imaging technique
like EEG
[
Electroencephalogram: Getting the Big Picture with EEGs
]
or fMRI
[
Functional Magnetic Resonance Imaging: The State of the Art
]
, but it can be used
along with them. TMS uses a magnetic pulse or oscillating magnetic fields to temporarily
induce or suppress electrical activity in the brain. It doesn’t require large machines, just
a small device around the head, and — so far as we know — it’s harmless with no
aftereffects.

Neurons communicate using electrical pulses, so being able to produce electrical
activity artificially has its advantages. Selected regions can be excited or suppressed,
causing hallucinations or partial blindness if some part of the visual cortex is being
targeted. Both uses help discover what specific parts of the brain are for. If the subject
experiences a muscle twitching, the TMS has probably stimulated some motor control neurons,
and causing hallucinations at different points in the visual system can be used to discover
the order of processing (it has been used to discover where vision is cut out during
saccades
[
Glimpse the Gaps in Your Vision
]
, for example).

Preventing a region from responding is also useful: if shutting down neurons in a
particular area of the cortex stops the subject from recognizing motion, that’s a good clue
as to the function of that area. This kind of discovery was possible before only by finding
people with localized brain damage; now TMS allows more structured experiments to take
place.

Coupled with brain imaging techniques, it’s possible to see the brain’s response to a
magnetic pulse ripple through connected areas, revealing its structure.

Of the many unscientific nuggets of wisdom about the brain that many people believe, the
most common may be the “fact” that we use only 10% of our brains.

In a recent survey of people in Rio de Janeiro with at least a college education,
approximately half stated that the 10% myth was true.
¹
There is no reason to suppose the results of a similar survey conducted
anywhere else in the world would be radically different. It’s not surprising that a lot of
people believe this myth, given how often it is claimed to be true. Its continued popularity
has prompted one author to state that the myth has “a shelf life longer than lacquered Spam”.
²

Neuropsychology is the study of patients who have suffered brain damage and the
psychological consequences of that brain damage. As well as being a vital source of
information about which bits of the brain are involved in doing which things,
neuropsychology also provides a neat refutation of the 10% myth: if we use only 10% of our
brains, which bits would you be happy to lose? From neuropsychology, we know that losing
any
bit of the brain causes you to stop being able to do something or
being able to do it so well. It’s all being used, not just 10% of it.

Admittedly we aren’t clear on exactly what each bit of the brain does, but that doesn’t
mean that you can do without 90% of it.

Neuropsychology has other uses aside from disproving unhelpful but popularly held
trivia. By looking at which psychological functions remain after the loss of a certain brain
region, we can tell what brain regions are and are not necessary for us to do different
things. We can also see how functions group and divide by looking at whether they are always
lost together or lost only in dissimilar cases of brain damage. Two of the famous early
discoveries of neuropsychology are two distinct language processing regions in the brain.
Broca’s area
(named after the neuropsychologist Paul Broca) is in the
frontal lobe and supports understanding and producing structure in language. Those with
damage to Broca’s area speak in stilted, single words.
Wernicke’s area
(on the junction between the temporal and parietal lobes and named after Carl Wernicke)
supports producing and understanding the semantics of language. People with brain damage to
Wernicke’s area can produce grammatically correct sentences, but often with little or no
meaning, an incomprehensible “word salad.”

Another line of evidence against the 10% myth is brain imaging research
[Hacks
#2
through
#4
]
, which has grown
exponentially in the last couple of decades. Such techniques allow the increased blood flow
to be measured in certain brain regions during the performance of cognitive tasks. While
debate continues about the degree to which it is sensible to infer much about functional
localization from imaging studies, one thing they make abundantly clear is that there are no
areas of the brain that are “black holes” — areas that never “light up” in response to some
task or other. Indeed, the neurons that comprise the cortex of the brain are active to some
degree all the time, even during sleep.

A third line of argument is that of evolutionary theory. The human brain is a very
expensive organ, requiring approximately 20% of blood flow from the heart and a similar
amount of available oxygen, despite accounting for only 2% of body weight. The evolutionary
argument is straightforward: is it really plausible that such a demanding organ would be so
inefficient as to have spare capacity 10 times greater than the areas being usefully
employed?

Fourth, developmental studies indicate that neurons that are not employed early
in life are likely never to recover and behave normally. For example, if the visual system
is not provided with light and stimulation within a fairly narrow developmental window, the
neurons atrophy and vision never develops. If the visual system is deprived of a specific
kind of stimulation, such as vertical lines, it develops without any sensitivity to that
kind of stimulus. Functions in other parts of the brain similarly rely on activation to
develop normally. If there really were a large proportion of neurons that were not used but
were instead lying in wait, likely they would be useless by puberty.

It can be seen, then, that the 10% myth simply doesn’t stand up to critical thinking.
Two factors complicate the picture slightly, however; both have been used to muddy the
waters around the claim at some stage.

First, people who suffer hydrocephalus in childhood have been seen to have large “holes”
in the middle of their brains and yet function normally (the holes are fluid-filled
ventricles
that are present in every brain but are greatly enlarged
in hydrocephalus). This condition has been the focus of sensationalist television
documentaries, the thrust of which is that we can get on perfectly well without much of our
brains. Such claims are willfully misleading — what such examples actually show is the
remarkable capacity of the brain to assign functioning to alternative areas if there are
problems with the “standard” areas during a specific time-point in development. Such
“neuronal plasticity,” as it is known, is not seen following brain damage acquired in
adulthood. As discussed earlier, development of the brain depends on activity — this same fact
explains why hydrocephalitic brains can function normally and makes having an unused 90%
extremely unlikely.

Second, there is actually a very disingenuous sense in which we do “use” only 10% of our
brains. The glial cells of the brain outnumber the neurons by a factor of roughly 10 to 1.
Glial cells play a supporting role to the neurons, which are the cells that carry the
electrochemical signals of the brain. It is possible, therefore, to note that only
approximately 10% of the cells of the cortex are directly involved in cognition.

This isn’t what proponents of the 10% theory are referring to, however. Instead, the
myth is almost always a claim about mind, not brain. The claim is analogous to arguing that
we operate at only 10% of our potential (although “potential” is so immeasurable a thing, it
is misleading from the start to throw precise percentages around).

Uri Geller makes explicit the “untapped potential” interpretation in the
introduction to
Uri Geller’s Mind-Power Book:

The confusion between brain and mind blurs the issue, while lending the claim an air of
scientific credibility because it talks about the physical brain rather than the unknowable
mind.

But it’s just not true that 90% of the brain’s capacity is just sitting there unused. It
is true that our brains adjust their function according to experience
[
Build Your Own Sensory Homunculus
]
— good news
for the patients studied by neuropsychology. Many of them recover some of the ability they
have lost. It is also true that the brain can survive a surprisingly large amount of damage
and still sort of work (compare pouring two pints of beer down your throat and two pints of
beer into your computer’s hard disk drive for an illustration of the brain’s superior
resistance to insults). But neither of these facts mean that you have exactly 90% of
untapped potential — you need all your brain’s plasticity and resistance to insult to keep
learning and functioning across your life span.

In summary, the 10% myth isn’t true, but it does offer an intuitively seductive promise
of the possibility of self-improvement. It has been around for at least 80 years, and
despite having no basis in current scientific knowledge and being refuted by at least 150
years of neuropsychology, it is likely to exist for as long as people are keen to aspire to
be something more than they are.