I've been reading a lot on neuroscience and neuroanatomy lately and the 8 functions seem to be associated with particular regions of the brain.
Each cerebral hemisphere is divided in into 4 lobes; Frontal, Parietal, Temporal and Occipital. The frontal lobes are the home of the motor cortex, where voluntary movements are triggered. The parietal lobes are the home of the somatosensory (touch and body position) cortex, the temporal lobes are the home of the auditory (sound) cortex, and the occipital lobes are the home of the visual cortex; these are where sensory information is first processed. This suggests a basic split between action (T/F) in the front and perception (S/N) in the back.
In the areas not part of motor or sensory cortex ares the areas of association cortex, where sensory data is analyzed and compared with one's memories and factual knowledge and then manipulated and sent to the motor cortex. It is these association areas, IMO, in which where we can find the neurological correlations of Jung's functions. The association areas are the pre-frontal cortex (PFC), the parietal association cortex (PAC) and the temporal association cortex (TAC). The the pre-frontal cortex can be further divided into the dorsal-lateral (top) PFC and orbital-frontal (bottom) PFC.
PFC: Planning, self-control, manipulating mental images, motivation, short-term memory
PAC: analyzing incoming sensory information in terms of spatial relationships between entities in real or abstract space. (often called "where" processing)
TAC: analyzing incoming sensory information in relation to past experience, categories, and factual knowledge. (often called "what" processing)
Finally, there is an asymmetry in the function of the two hemispheres. The left hemisphere is more focused and literal while the right hemisphere more gestalt and broad. If you are shown a picture of a cow the left hemisphere would generate associations closed centered on the cow itself while the right hemisphere would generate associations of a more broad character, like drinking milk this morning, memories of growing up on a farm, etc. This suggests a dichotomy of F and N on the right and T and S on the left.
Ti = Left Dorsal-Lateral PFC
Fi = Right Dorsal-Lateral PFC
Te = Left Orbital-Frontal PFC
Fe = Right Orbital-Frontal PFC
Si = Left TAC
Ni = Right TAC
Se = Left PAC
Ne = Right PAC