They are the compound direct object of the setup line of a lame joke.
Encephalography may refer to: Electroencephalography Hemoencephalography Magnetoencephalography http://en.wikipedia.org/wiki/Encephalography
A meal preparation is when you or somebody prepares something for them and their family to eat.
Christmas, usually
Fasting or drinking only clear liquids is necessary for four hours before the test.