We're No Slaves to Our Senses
By Stuart Derbyshire
Spiked, August 24, 2007
Edited by Andy Ross
Making up the Mind: How the Brain Creates our Mental World
Blackwell, 2007, 232 pages
Positron emission tomography (PET) involves the injection of a radioactive
isotope that rapidly decays in the bloodstream of the volunteer. As the
isotope decays it emits positrons that can be detected outside the body. The
brain gets its energy from the bloodstream. Areas that are more active
receive more blood, so more positrons are detected from those areas. Using
this technique, a picture of the brain at work can be built.
Technologies to represent brain function only provide a limited amount of
detail. Imagine trying to figure out what is happening inside the Empire
State Building by watching the lights go on and off. You might get some idea
as to the internal function, but not much. The same problem faces those of
us who hope to understand brain function.
But there is a further
reason why our understanding is lagging behind expectation. The facts
provided by brain imaging are the wrong sorts of facts.
Chris Frith has dedicated much of his academic career to the study of
schizophrenia. Frith describes schizophrenia as the consequence of damage to
brain function. He argues that if we can understand how mental function
comes about in people without schizophrenia, we will be better placed to
understand how mental function goes wrong in people with schizophrenia.
Normal brains do all kinds of things without us being aware of it. If we
were always processing sensation we would have no time for anything more
interesting: "Couldn't the system be tuned so that the sensory signals
always dominated our experience? Then hallucinations could not occur. In
fact, this is a bad idea, for many reasons. Sensory signals are simply too
unreliable. But more importantly, such domination would make us slaves to
Our minds are not drowned or dissolved by the senses.
Human beings are self-located within sensory experience, but we are not
sensorily immersed. Our intuition of ourselves as particular things with
particular location and experience is opened up by our senses. Frith thinks
our sense of the world is an illusion: "It may feel as if we have direct
access, but this is an illusion created by our brain." And he is ambivalent
about free will: "I am firmly convinced that I am a product of my brain ...
I have a very strong experience of free will."
that reality is illusory and free will is just a manufactured state of mind
are both far too strong. Our limited direct access to the world is a problem
because the world does not divide itself into fact-sized chunks. It is
through our relationship with the world that we can come to divide it. The
facts that we can lay claim to about the world are selected from an almost
infinite number of potential facts, but we can have great confidence that
the facts we are gathering are real.
Frith understates the role of
inquiry in constructing a real representation of the world. Inquiry brings
human beings into an understanding of the world that continues to more
closely approximate the way the world truly is. The constraints that our
brain places upon inquiry do not dictate reality but rather enable a
specific viewpoint to flourish and an independent existence to announce
Constraint upon our embodied action is also necessary for
free will. If every action were driven by conscious agency then we would be
overwhelmed by the effort of trying to control all the relevant parameters
with the requisite precision just as our senses would be drowned by
information if there were no filtering.
The negotiation of constraint
and indeterminacy cannot be located in parts of the brain and recorded on a
graph. That negotiation is an active, lived process and free will is
possible because of the ability to interrogate nature. The fundamental
mistake that Frith makes is to believe that agency or free will are products
only of the human brain.
The Economist, August 30, 2007
Edited by Andy Ross
Magnetoencephalography (MEG) detects magnetic signals produced by the
electrical activity of brain cells. MEG signals are in the femtotesla range,
about a billionth of the strength of the Earth's magnetic field.
Apostolos Georgopoulos and his colleagues at the University of Minnesota,
Minneapolis, think MEG could be adapted for medical use. In a recent paper
in the Journal of Neural Engineering, they report that the general hum of
brain activity might contain diagnostic information.
found a characteristic pattern in the magnetic fluctuations of healthy
people's brains. He asked ten volunteers to stare at a point of light as
they lay under his machine. Each run of the experiment used 248 sensors and
every sensor took 45,000 readings over the course of a run.
wondered whether the brains of people with neurological diseases might have
different magnetic patterns. He invited patients with a clear diagnosis of
one of six afflictions to lie in his machine. Then he recorded the magnetic
fluctuations of their brains.
He analysed the results using
discriminant function analysis. This allows complicated data to be reduced
to a small number of components whose co-ordinates can be plotted on a
graph. Each of the diseases produced a distinct cluster. Healthy brains
produced a cluster that did not overlap with any of the diseases.