The Unique Fiber Anatomy of Middle Temporal Gyrus Default Mode Connectivity

Abstract

BACKGROUND The middle temporal gyrus (MTG) is understood to play a role in language-related tasks such as lexical comprehension and semantic cognition. However, a more specific understanding of its key white matter connections could promote the preservation of these functions during neurosurgery. OBJECTIVE To provide a detailed description of the underlying white matter tracts associated with the MTG to improve semantic preservation during neurosurgery. METHODS Tractography was performed using diffusion imaging obtained from 10 healthy adults from the Human Connectome Project. All tracts were mapped between cerebral hemispheres with a subsequent laterality index calculated based on resultant tract volumes. Ten postmortem dissections were performed for ex vivo validation of the tractography based on qualitative visual agreement. RESULTS We identified 2 major white matter bundles leaving the MTG: the inferior longitudinal fasciculus and superior longitudinal fasciculus. In addition to long association fibers, a unique linear sequence of U-shaped fibers was identified, possibly representing a form of visual semantic transfer down the temporal lobe. CONCLUSION We elucidate the underlying fiber-bundle anatomy of the MTG, an area highly involved in the brain's language network. Improved understanding of the unique, underlying white matter connections in and around this area may augment our overall understanding of language processing as well as the involvement of higher order cerebral networks like the default mode network in these functions.

Convergent Functional Changes of Default Mode Network in Mild Cognitive Impairment Using Activation Likelihood Estimation

“…Another noteworthy area of FC decline is the middle temporal gyrus. The middle temporal gyrus (MTG) is understood to play a role in language-related tasks such as lexical comprehension and semantic cognition (Briggs et al, 2021 ). Furthermore, an increase of FC in the middle frontal gyrus may also be allowed to compensate for a decrease of FC in the medial temporal gyrus (Gardini et al, 2015 ).…”

Parcellation‐based tractographic modeling of the salience network through meta‐analysis

“…For instance, as mentioned in Table 2 , one could see a certain degree of individual variability within specific white matter connections by comparing the average amount of tracts in all subjects versus only subjects in which the tracts were identified. Furthermore, while this methodology has been applied by our team over numerous other cortical regions, we have found that our results are relatively robust to the number of participants usually included (i.e., averages of 80 subjects are likely similar to those of 10 subjects), and there is always some degree of individual variability with tractographic analyses (Briggs, Tanglay, et al., 2021 ; Palejwala et al., 2021 ; Sheets, Briggs, Dadario, et al., 2021 ). These differences are largely due to the inherent uniqueness of neural structures between individuals.…”

“…As such, their speculative functions may be more easily identifiable compared to the FAT. Given the short nature of these U‐fibers with closely located cortical regions, they are generally described to facilitate quick information transfer between different regions within a network, usually in a single brain lobe (Briggs, Tanglay, et al., 2021 ).…”

“…Publicly available imaging data from the HCP were obtained for this study from the HCP database ( http://humanconnectome.org , release Q3) to be utilized for structural analyses as elucidated elsewhere (Briggs, Lin, et al., 2021 ; Briggs, Tanglay, et al., 2021 ; Palejwala et al., 2021 ; Sandhu et al., 2021 ; Sheets, Briggs, Dadario, et al., 2021 ; Tanglay et al., 2021 ). Diffusion imaging with corresponding T1‐weighted images from 25 healthy, unrelated subjects was analyzed during fiber tracking analysis (subject IDs: 100307, 103414, 105115, 110411, 111312, 113619, 115320, 117112, 118730, 118932, 100408, 115320, 116524, 118730, 123925, 148335, 148840, 151526, 160123, 178950, 188347, 192540, 212318, 366446, 756055).…”

Reducing the Cognitive Footprint of Brain Tumor Surgery

“…(100). This is important given that outdated brain atlases based on group-averaged data or single subjects may overlook hubs unique to specific individuals, such as in the temporal pole which is often considered non-eloquent and therefore "safe to resect" (101). Recent improvements in connectomic data has also allowed others to expand the clinical utility of DES in identifying critical hubs on an individualized basis (89,102).…”