While we're waiting for Mr. Reed, I found some interesting tidbits about the 8 Jungian functions in a book by Lenore Thomson called "Personality Type: An Owner's Manual".
She says there has been research done using PET scanning that locates the functions in the brain thusly:
Left Brain.....Right Brain
Te................Ne
Fe................Se
Si.................Fi
Ni.................Ti
The left brain is described as verbal, linear, and rational while the right brain is visual, tactile, physical, and holistic. Matching this up with the function locations you will see that the judging functions are extraverted on the left side while the perceiving functions are extraverted on the right. And given the way that J and P are defined, this explains why the J and P type descriptions are so similar to the left and right brain attributes.
This gives rise to these, hopefully better, descriptions of the 8 functions:
Te - left brain - verbal analysis and abstract logic
Ti - right brain - visual, tactile, and spatial logic
Fe - left brain - recognizes signs of relationships and draws rational conclusions about behavior
Fi - right brain - subjective ideas about human values
Se - right brain - physicality and material investment
Si - left brain - acquires facts and impressions (also keeps us in touch with what matters to us)
Ne - right brain - holistic, what we usually think of as intuitive
Ni - left brain - moves beyond boundaries of language (not really sure what that means)