Inferior Parietal Lobule

Architectonic parcellation of the parietal lobes of eight human brains, with special attention paid to the inferior parietal lobule, resulted in a map that bore a close relationship to previous maps and took into consideration modern data on physiology and connections. Two general parietal zones were distinguished, one above and the other below the intraparietal sulcus, similar to the dorsal-ventral distinction suggested for the frontal lobe. Five areas were recognized in the inferior parietal lobule, of which areas parietal areas EG (PEG), G (PG), and occipitoparietal G (OPG) were in the angular gyrus. A lateralization toward the right was found for area PEG, an area structurally similar to the visually related cortices of the posterior superior parietal region. A lateralization toward the left was found for area PG, but only in brains with a larger left planum temporale. The asymmetry in area PG seemed to be linked to other asymmetries present in language areas, whereas the right-sided area PEG preponderance showed no relation to the language asymmetries.