Redefining Reality - The Intellectual Implications of Modern Science

the composition of the molecules. By measuring this relaxation
determine what kinds of substances are inside.
This technique allows us to do what CAT scans do—look
inside the brain without having to physically go into it—but at
a higher resolution and with no cancer-causing radiation.
MRIs, however, still provide only snapshots; they allow us to see
tumors and structural abnormalities but not the brain at work. For
this, we need positron emission tomography (PET) scans.
In a PET scan, a radioactive form of oxygen attached to a sugar
molecule is injected into the patient and is taken into the blood
and used by cells in the same way as normal sugars.
The radioactive molecule in the blood allows us to detect, at
any given moment, which part of the brain is active because it
results in a spike in the emitted radioactivity from the sugar in
that part of the brain.
The advantage of the PET scan is that instead of looking at
architecture, we are now looking at process. We can literally
see parts of the brain light up in various sequences when the
person engages in different sorts of activities.
With these new tools, psychologists believed that they could decode
which parts of the brain were responsible for what. This research
included not only behaviors, such as speech and movement, but
elements of internal consciousness, such as falling in love or
thinking someone untrustworthy. This project continues to provide
us with unexpected insights into human behavior.
It has also shown us that we are not, as we had thought,
autonomous individuals acting on the world through the force
of our will.
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