Anatomy and White Matter Connections of the Middle Frontal Gyrus.

ABSTRACT Background The middle frontal gyrus (MFG) is involved in attention, working memory, and language-related processing. A detailed understanding of the subcortical white matter tracts connected within the MFG can facilitate improved navigation of white matter lesions in and around this gyrus as well as explain post-operative morbidity following surgery. Objective We aim to characterize the fiber tracts within the MFG based on their connection to neuroanatomic structures through the use of DSI-based fiber tractography and validating this with gross anatomic dissection for qualitative visual agreement. Methods Tractography analysis was completed using diffusion imaging data of ten healthy, adult subjects enrolled in the Human Connectome Project. We assessed the MFG as a whole component based on its fiber connectivity with other neural regions. Mapping was completed on all tracts within both hemispheres, with resultant tract volumes being used to calculate a lateralization index. A modified Klingler technique was used on ten postmortem dissections to demonstrate the location and orientation of major tracts. Results Two major connections of the MFG were identified: the superior longitudinal fasciculus (SLF) connecting the MFG to parts of the inferior parietal lobule, posterior temporal lobe, and lateral occipital cortex; and the inferior fronto-occipital fasciculus (IFOF) which connected the MFG to the lingual gyrus and cuneus. Intra- and inter-gyral “U”-shaped fibers were also identified. Conclusions Subcortical white matter pathways integrated within the MFG include the SLF and IFOF. The MFG is implicated in a variety of tasks involving attention and memory making it an important cortical region. Post-operative neurologic outcomes related to surgery in and around the MFG may be clarified in the context of the anatomy of fiber-bundles highlighted in this study.