Figure 2.

This panel describes the most superficial long associative fascicle running through the TPO area, the SLF. Proceeding in a latero-medial direction during a left-hemisphere dissection, we located the indirect and direct components of the SLF, which is divided into one direct (AF) and two indirect anterior and posterior components (respectively, the SLF II and III). (A) Starting at the tempo-parietal junction, we identified a posterior group of temporo-parietal fibres (blue arrow) connecting the posterior third of the STG and MTG (pink circle) with the ventral part of the IPL (blue circle, red pin). (B) After removal of the lateral third of the central lobule, we followed the complete course of an anterior group of fibres (blue arrows) between the dorsal part of the IPL (green circle) and the posterior part of the STG (yellow circle) to the IFG. (C) We gently separated and lifted the posterior indirect component of the SLF from the deeper fibres of the AF (pink circle, pink pin). (D) We completed the exposure of the AF. These fibres directly connect the posterior part of the STG and MTG to the frontal lobe with a C-shaped course around the posterior insula beneath the IPL (red arrow). Within the frontal region we isolated the AF terminations (blue tags) directed to the Pop (green circle) and the pars triangularis (yellow circle) of the IFG and the MFG (violet circle). CS, central sulcus; IFG, inferior frontal gyrus; MTG, middle temporal gyrus; Op, opercularis pars of the IFG; PostCG, post-central gyrus; PreCG, pre-central gyrus; STG, superior temporal gyrus; Tr, pars triangularis of the IFG.