Mapping the Human Middle Longitudinal Fasciculus Through a Focused Anatomo-imaging Study: Shifting the Paradigm of its Segmentation and Connectivity Pattern. (16th November 2020)

• Record Type: Journal Article
• Authors: Kalyvas, Aristotelis; Koutsarnakis, Christos; Komaitis, Spyridon; Skandalakis, Georgios P; Karavasilis, Efstratios; Christidi, Foteini; Kongkham, Paul N; Zadeh, Gelareh; Gentili, Fred; Duffau, Hugues; Stranjalis, George
• Is Part Of: Neurosurgery. Volume 67(2010)Supplement 1
• Publication Date: 2020-11-16
• Subjects: Nervous system -- Surgery -- Periodicals; 617.48005
• DOI: 10.1093/neuros/nyaa447_806
• Languages: English
• ISSNs: 0148-396X

Abstract

Abstract: INTRODUCTION: The Middle Longitudinal Fasciculus (MdLF) was initially identified in humans as a discrete subcortical pathway connecting the Superior Temporal Gyrus (STG) to the Angular Gyrus (AG). Further anatomo-imaging studies however proposed more sophisticated but conflicting connectivity patterns and have created a vague perception on its functional anatomy. METHODS: With this in mind, we opted to re-examine the inherent morphology of the MdLF through a detailed combined methodology entailing focused white matter dissections in 20 adult, normal, cerebral hemispheres further augmented by a tailored DTI protocol in 35 healthy participants from the Human Connectome dataset. RESULTS: Three segments and connectivity patterns were consistently recorded: the MdLF-I, connecting the dorsolateral Temporal Pole (Area TAr) and STG to the Superior Parietal Lobule/Precuneus, through the Heschl's gyrus; the MdLF-II, connecting the dorsolateral Temporal Pole (Area TAr) and the STG with the Parieto-occipital arcus through the posterior transverse gyri and the MdLF-III connecting the most anterior part of the TP (areas TG and TAp)to the posterior border of the occipital lobe through the AG. CONCLUSION: The lack of an established termination pattern to the AG and the fact that no significant leftward asymmetry is disclosed, tend to shift the paradigm away from language function. Conversely, the theory of "where" and "what" auditory pathways, the essential relationship of the MdLF with the auditory cortex and the functional role of the cortical areas implicated in its connectivity tend to shift the paradigm towards auditory function. Allegedly, the MdLF-I and MdLF-II segments could underpin the perception of auditory representations whereas the MdLF-III could potentially subserve the integration of auditory and visual information.