Answer to Question 1
The MRI measures variations in magnetic fields. It then computes and depicts cross sections of organs such as
the brain with great clarity. It is noninvasive and allows for visualization of all but the tiniest brain structures. Its
major problem is the claustrophobic reaction some people have to the procedure. PET scans track substances as
they are metabolized by the brain. They can show how the brain is functioning. They can help identify areas that
aren't functioning normally that might not be obvious anatomically. Their major problem is low-fidelity pictures
which have so far limited their value. The fMRI measures changes in blood flow in the brain. It is possible to
map ongoing psychological activity and show which areas of the brain are involved in different activities.
However, like MRIs these are very sensitive to movement, which can cause false results. Also fMRIs are often
very hard to interpret.
Answer to Question 2
During sleep, defenses are lowered and repressed material begins to come out. However,
some material is so threatening it comes out in disguised form. Dreams have a manifest
content, the obvious theme of the dream, and a latent content, the actual disguised motives
and impulses. Analyzing the dream helps uncover the latent content.
The thorax of apes, including humans, is broad but shallow in contrast to the narrower, deeper chest
CT Brain Scans
How lateral inhibition produces contrast enhancement. (Based on Ratliff, 1972.)
Brain metabolism in a schizophrenic individual (left) and a normal individual (right). These scans o
Bar-eye phenotypes in contrast to the wild-type eye in Drosophila
MRI scans of normal elderly person compared to one with Alzheimer's