Spatial distribution of hand‐grasp motor task activity in spinal cord functional magnetic resonance imaging

Abstract

Upper extremity motor paradigms during spinal cord functional magnetic resonance imaging (fMRI) can provide insight into the functional organization of the cord. Hand‐grasping is an important daily function with clinical significance, but previous studies of similar squeezing movements have not reported consistent areas of activity and are limited by sample size and simplistic analysis methods. Here, we study spinal cord fMRI activation using a unimanual isometric hand‐grasping task that is calibrated to participant maximum voluntary contraction (MVC). Two task modeling methods were considered: (1) a task regressor derived from an idealized block design (Ideal) and (2) a task regressor based on the recorded force trace normalized to individual MVC (%MVC). Across these two methods, group motor activity was highly lateralized to the hemicord ipsilateral to the side of the task. Activation spanned C5–C8 and was primarily localized to the C7 spinal cord segment. Specific differences in spatial distribution are also observed, such as an increase in C8 and dorsal cord activity when using the %MVC regressor. Furthermore, we explored the impact of data quantity and spatial smoothing on sensitivity to hand‐grasp motor task activation. This analysis shows a large increase in number of active voxels associated with the number of fMRI runs, sample size, and spatial smoothing, demonstrating the impact of experimental design choices on motor activation.

MRI mapping of hemodynamics in the human spinal cord

“…Early reports of BOLD signal changes in the spinal cord achieved with a hypercapnic gas inhalation challenge were roughly 0.17 %BOLD/mmHg (based on a reported 0.6 mean percent signal change with a 3.5mmHg mean PETCO2 change ( 17)), as compared to 0.01 %BOLD/mmHg for the group SCVR across the whole spinal cord region-of-interest in this study. This difference may be due to smaller sample sizes inflating parameter estimates (22), or because of the different methods of averaging -our measure is obtained from the group level parameter estimates, so they are not directly comparable to the previous study. The mean ventral gray matter SCVR is about 0.02 %BOLD/mmHg, which is about an order of magnitude lower than similar mean gray matter cerebrovascular reactivity measures (23,24) and is to be expected because of increased SNR in the brain.…”

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Recent developments and future avenues for human corticospinal neuroimaging

“…Depending on the muscles of the upper limbs being activated during the task and accordingly innervated by specific spinal nerves (i.e., myotomes), the rostrocaudal distribution of elicited activation varies along the cervical spinal cord ( Stroman et al, 1999 ; Madi et al, 2001 ; Maieron et al, 2007 ; Smith and Kornelsen, 2011 ; Kinany et al, 2019 ; Barry et al, 2021 ). Most recently, a study exploring hand-grasp (i.e., fist-clenching) motor task activity provided more detailed information on the functional organization of the spinal cord ( Hemmerling et al, 2023 ), as compared to previous studies reporting varying localization of rostrocaudal activation ( Stroman et al, 1999 ; Stroman and Ryner, 2001 ; Giulietti et al, 2008 ; Ng et al, 2008 ; Islam et al, 2019 ). Spinal fMRI revealed areas of activity spanning cervical levels C5-C8, primarily focusing on the C7 spinal cord segment ( Hemmerling et al, 2023 ).…”

“…Most recently, a study exploring hand-grasp (i.e., fist-clenching) motor task activity provided more detailed information on the functional organization of the spinal cord ( Hemmerling et al, 2023 ), as compared to previous studies reporting varying localization of rostrocaudal activation ( Stroman et al, 1999 ; Stroman and Ryner, 2001 ; Giulietti et al, 2008 ; Ng et al, 2008 ; Islam et al, 2019 ). Spinal fMRI revealed areas of activity spanning cervical levels C5-C8, primarily focusing on the C7 spinal cord segment ( Hemmerling et al, 2023 ).…”