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

Abstract

Although 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 human TPC are available using modern neuroanatomical techniques. The present study investigated TPC with combined analysis of several different cellular, neurochemical, and pathological markers finding that this area is not homogenous as at least six different areas extend into TPC with another area being unique to the polar region. Specifically, perirhinal area 35 extends into the posterior TPC while 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 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 TPC is defined as 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 temporal insular cortex and named as area TI after Beck (1934). Finally, a dysgranular TPC region which capped the tip with some extension into the dorsal aspect of the TPC is defined as temporopolar area TG. Therefore, human TPC actually includes areas TAr and TI, anterior parts of areas 35, 36, TE, and TAp, and the unique temporopolar area TG.

The Semantic Network at Work and Rest: Differential Connectivity of Anterior Temporal Lobe Subregions

“…Until recently, the ATL has been viewed as one homogenous region due to the low spatial specificity of neuropsychological data. However, cytoarchitectural differences within the ATL hint at the presence of distinct, yet graded subregions (Brodmann, 2006;Ding et al, 2009). Recent neuroimaging, neurostimulation, electrophysiology, and detailed patient assessments suggest that the center point of the multimodal hub region sits within the ventral ATL (vATL; Lüders et al, 1986;Lüders et al, 1991;Pobric et al, 2007;Butler et al, 2009;Lambon Ralph et al, 2009;Binney et al, 2010;Mion et al, 2010;Visser and Lambon Ralph, 2011;Shimotake et al, 2015).…”

“…For example, the anterior superior temporal gyrus (aSTG) and superior temporal sulcus (STS) may be particularly involved in processing the meaning of auditory and verbal stimuli (Scott et al, 2000;Spitsyna et al, 2006;Visser and Lambon Ralph, 2011; and may reflect structural connections to primary auditory regions (Morán et al, 1987;Binney et al, 2012). Alternatively, the aSTG's structural connection to the inferior frontal gyrus (IFG) (Duffau et al, 2005;Friederici, 2011) could suggest a role in semantic control .…”

“…First, only one location was studied so comparison was not possible. Second, there is signal loss and distortion in the ATL (Binney et al, 2010;Embleton et al, 2010;Visser et al, 2010b;Halai et al, 2014), an issue highlighted in previous seedbased and whole-brain resting-state studies (Ding et al, 2009;Zuo et al, 2012;Wig et al, 2014).…”

A Comprehensive Protocol for Manual Segmentation of the Medial Temporal Lobe Structures

“…Historically, there have been conflicting descriptions in the literature for some MTL structures. In some cases of segmenting the PRC, for example, the collateral sulcus has been described as interrupted 35,36 , but this has previously been described in other literature as a short CS which does not exceed the level of the limen insulae 30 . This difference in interpretation has led to different anterior border definitions for the PRC, and this might explain to some extent why variations have been observed in segmentations of individual structures across different studies.…”

“…By drawing information from various separate tracing protocols for these structures [18][19][20][21][22]25,[28][29][30][31] , as well as from anatomical analyses and atlases 23,[32][33][34][35][36][37] , the present protocol presents a comprehensive set of guidelines that address inconsistencies in the extant literature.…”