The connectivity-based parcellation of the angular gyrus: fiber dissection and MR tractography study

The angular gyrus (AG) wraps the posterior end of the superior temporal sulcus (STS), so it is considered a continuation of the superior temporal gyrus (STG)/ middle temporal gyrus (MTG) and forms the inferior parietal lobule (IPL) with the supramarginal gyrus (SMG). The AG was functionally divided in the literature, but there is no fiber dissection study in this context. This study divided AG into superior (sAG) and inferior (iAG) parts by focusing on STS. Red, blue silicone-injected eight and four non-silicone-injected human cadaveric cerebrums were dissected via the Klingler method focusing on the AG. White matter (WM) tracts identified during dissection were then reconstructed on the Human Connectome Project 1065 individual template for validation. According to this study, superior longitudinal fasciculus (SLF) II and middle longitudinal fasciculus (MdLF) are associated with sAG; the anterior commissure (AC), optic radiation (OR) with iAG; the arcuate fasciculus (AF), inferior frontooccipital fasciculus (IFOF), and tapetum (Tp) with both parts. In cortical parcellation of AG based on STS, sAG and iAG were associated with different fiber tracts. Although it has been shown in previous studies that there are functionally different subunits with AG parcellation, here, for the first time, other functions of the subunits have been revealed with cadaveric dissection and tractography images.