The role of the frontal aslant tract and premotor connections in visually guided hand movements

Abstract

Functional neuroimaging and brain lesion studies demonstrate that secondary motor areas of the frontal lobe play a crucial role in the cortical control of hand movements. However, no study so far has examined frontal white matter connections of the secondary motor network, namely the frontal aslant tract, connecting the supplementary motor complex and the posterior inferior frontal regions, and the U-shaped dorsal and ventral premotor fibers running through the middle frontal gyrus. The aim of the current study is to explore the involvement of the short frontal lobe connections in reaching and reach-to-grasp movements in 32 right-handed healthy subjects by correlating tractography data based on spherical deconvolution approach with kinematical data. We showed that individual differences in the microstructure of the bilateral frontal aslant tract, bilateral ventral and left dorsal premotor tracts were associated with kinematic features of hand actions. Furthermore, bilateral ventral premotor connections were also involved in the closing grip phase necessary for determining efficient and stable grasping of the target object. This work suggests for the first time that hand kinematics and visuomotor processing are associated with the anatomy of the short frontal lobe connections.

Damage to the Frontal Aslant Tract Accounts for Visuo-Constructive Deficits in Alzheimer’s Disease

“…In its rostral part (around pre-SMA) the FAT is intermingling and overlapping with FST [16], whereas, caudally, FAT is running in a little more anterolateral side than FST [16]. Moreover, the present findings are supported by recent evidence of the role played by FAT in the visually guided hand movements [51], necessary to perform the grapho-motor task underlying the drawing tests.…”

The frontal aslant tract (FAT) and its role in speech, language and executive function

“…That is, broadly defined, interactions between these regions establish action plans for the output of sequential (non-speech) motor programs, and together decide on a "winning" action plan, implemented via downstream interactions in basal ganglia and motor cortex. Consistent with this idea are studies that show that diffusion FA of the right FAT is related to deficits in constructional apraxia (Serra et al, 2017), and to more efficient visuomotor processing during manual movements, resulting in smoother movement trajectories (Budisavljevic et al, 2017). This again points to the importance of this tract in sequential movement planning.…”

Anatomy and white matter connections of the inferior frontal gyrus

“…The pars opercularis is also recruited during phonological processing and production (Hagoort ). White matter connections corresponding to the FAT are thought to help coordinate the motor actions necessary for speech production (Martino et al ; Budisavljevic et al ; Szmuda et al ). Several studies have described a white matter pathway connecting the dorsal posterior SFG in the region of the supplementary motor area to Broca's area in the IFG (Lawes et al ; Oishi et al ).…”

“…The IFG indirectly mediates response inhibition by increasing the excitatory activity of the pre‐supplementary motor area as it directly influences the subthalamic nucleus to regulate and inhibit motor cortex output (Rae et al ). At least one study has implicated the FAT in motor inhibition processing of bilateral hand movements (Budisavljevic et al ), implicating this white matter bundle in transmitting motor inhibitory information from the IFG to the supplementary motor area.…”