Mapping temporo-parietal and temporo-occipital cortico-cortical connections of the human middle longitudinal fascicle in subject-specific, probabilistic, and stereotaxic Talairach spaces

Abstract

Originally, the middle longitudinal fascicle (MdLF) was defined as a long association fiber tract connecting the superior temporal gyrus and temporal pole with the angular gyrus. More recently its description has been expanded to include all long postrolandic cortico-cortical association connections of the superior temporal gyrus and dorsal temporal pole with the parietal and occipital lobes. Despite its location and size, which makes MdLF one of the most prominent cerebral association fiber tracts, its discovery in humans is recent. Given the absence of a gold standard in humans for this fiber tract, its precise and complete connectivity remains to be determined with certainty. In this study using high angular resolution diffusion MRI (HARDI), we delineated for the first time, six major fiber connections of the human MdLF, four of which are temporo-parietal and two temporo-occipital, by examining morphology, topography, cortical connections, biophysical measures, volume and length in seventy brains. Considering the cortical affiliations of the different connections of MdLF we suggested that this fiber tract may be related to language, attention and integrative higher level visual and auditory processing associated functions. Furthermore, given the extensive connectivity provided to superior temporal gyrus and temporal pole with the parietal and occipital lobes, MdLF may be involved in several neurological and psychiatric conditions such as primary progressive aphasia and other aphasic syndromes, some forms of behavioral variant of frontotemporal dementia, atypical forms of Alzheimer’s disease, corticobasal degeneration, schizophrenia as well as attention-deficit/hyperactivity disorder and neglect disorders.

Structural Disconnection of the Tool Use Network after Left Hemisphere Stroke Predicts Limb Apraxia Severity

“…In this context, it will be important to consider whether alternative fiber pathways, including the temporoparietal aslant tract ( Panesar et al. 2019 ) or middle longitudinal fasciculus ( Makris et al. 2017 ; Kalyvas et al.…”

Associative white matter connecting the dorsal and ventral posterior human cortex

“…The superior parietal lobule component of the middle longitudinal fasciculus (MdLF-SPL), like the MdLF-Ang, is an obliquely oriented tract which connects the temporal and parietal lobes. Unlike the MdLF-Ang, the MdLF-SPL's superior terminations are located medial to the IPS and are spread along the superior parietal lobule ( Figure 9b ; Martino et al 2013a;Makris et al 2013aMakris et al , 2017Kamali et al 2014a, b) . Just as the morphology of the posterior MdLF-Ang mirrors the pArc, the posterior morphology of the MdLF-SPL mirrors the TP-SPL, most notably in the sheet-like character it exhibits ( Figure 9a ).…”

“…Finally, it exhibits several areas of high endpoint density within the fusiform gyrus (see Supplementary Figures 6 and 8, see Supplementary Figure 3 The angular gyrus component of the middle longitudinal fasciculus (MdLF-Ang or MdLF-IPL) is a somewhat more obliquely oriented tract, as compared to the pArc and TP-SPL, and connects the temporal and parietal lobes. Specifically, it connects the anterior temporal regions to the angular gyrus, inferior parietal lobule (IPL) and some regions of posterior superior temporal gyrus (Menjot de Champfleur et al 2013;Makris et al 2013aMakris et al , 2017Kamali et al 2014a, b;Bajada et al 2015) . Its posterior morphology is quite similar to the pArc and is similarly characterized by its superior terminations being located lateral to the IPS (compare Figure 8a and Figure 6a ).…”

Effects of regiolects on the perception of developmental foreign accent syndrome

“…Being associated with the lesion maps of both paraphasia types, we were also able to demonstrate the relevance of the MdLF in language processing. The MdLF originates in the posterior superior temporal and parietal lobe, producing terminations along the course of the temporal cortex to the temporal pole (Makris et al 2016). Its role in language processing is still under debate (Tremblay and Dick 2016), although recent studies suggest that the MdLF is relevant for language processing, e.g.…”