Parcellation of human temporal polar cortex: a combined analysis of multiple cytoarchitectonic, chemoarchitectonic, and pathological markers.

Although the human temporal polar cortex (TPC), anterior to the limen insulae, is heavily involved in high-order brain functions and many neurological diseases, few studies on the parcellation and extent of the human TPC are available that have used modern neuroanatomical techniques. The present study investigated the TPC with combined analysis of several different cellular, neurochemical, and pathological markers and found that this area is not homogenous, as at least six different areas extend into the TPC, with another area being unique to the polar region. Specifically, perirhinal area 35 extends into the posterior TPC, whereas areas 36 and TE extend more anteriorly. Dorsolaterally, an area located anterior to the typical area TA or parabelt auditory cortex is distinguishable from area TA and is defined as area TAr (rostral). The polysensory cortical area located primarily in the dorsal bank of the superior temporal sulcus, separate from area TA, extends for some distance into the TPC and is defined as the TAp (polysensory). Anterior to the limen insulae and the temporal pyriform cortex, a cortical area, characterized by its olfactory fibers in layer Ia and lack of layer IV, was defined as the temporal insular cortex and named as area TI after Beck (J. Psychol. Neurol. 1934;41:129-264). Finally, a dysgranular TPC region that capped the tip with some extension into the dorsal aspect of the TPC is defined as temporopolar area TG. Therefore, the human TPC actually includes areas TAr and TI, anterior parts of areas 35, 36, TE, and TAp, and the unique temporopolar area TG.