Propriospinal Functional Connectivity During Hand Motor Control in Humans

1823 

Abstract Submission 

Matteo Grudny¹, Shahab Vahdat¹

¹University of Florida, Gainesville, FL

Matteo Grudny  
University of Florida
Gainesville, FL

Shahab Vahdat  
University of Florida
Gainesville, FL

Functional magnetic resonance imaging (fMRI) of the brain and spinal cord at the same time allows for novel investigation of the descending motor pathways in humans. The propriospinal pathway in humans is not well characterized and utilizing this innovative acquisition protocol and processing pipeline we report the detection of propriospinal functional connectivity during a motor control task. Specifically, we detect significant partial correlation of C3-C4 ipsilateral ventral horn activity with cortical, subcortical, brainstem, and cerebellar region activation during a motor control task in humans. Additionally, we observed significant functional connectivity with the C3-C4 ipsilateral dorsal horn in a subset of cerebellar and cortical regions. These results validate the sensitivity of our functional connectivity analysis and the importance of the propriospinal motor control pathway in hand motor control. Furthermore, this approach can be applied to gain insight on the dysfunctional descending motor and ascending sensory pathways in stroke patients and help guide therapeutic intervention.

We collected BOLD fMRI data covering the whole brain and the cervical cord (C1-T1 levels) using simultaneous multi-slice (SMS) EPI sequence on a 3T Prisma Siemens scanner (slice thickness: 4mm, resolution:1.6x1.6 mm2, TR:1.85 s). A MEDIC T2*w image was acquired with similar slice angle and thickness as EPI data (resolution 0.8x0.8 mm2). A T1w image was acquired for registration to the template (PAM50). During functional scans, 17 participants performed a manual grip force control task using their right hand in an event-related design paradigm. We employed a recently developed processing pipeline for analysis of spinal fMRI data called FASB [1]. The pipeline includes: a two-step motion correction procedure, slice-wise centerline alignment to T2*w image, independent component analysis (ICA) of spinal cord data to automatically identify non-neuronal related regressors, and automatic temporal SNR (tSNR) threshold selection based on MAP estimation. Functional connectivity analysis was conducted utilizing ROI based analysis. The ROIs included spinal levels C3-C4 and C5-C8, along with cortical, subcortical, brainstem, and cerebellar regions hypothesized to be involved in upper limb motor control. BASCO (BetA-Series Correlation), Pearson correlation during task-on periods, and partial correlation (by removing the effect of task paradigm presentation) were calculated and tested for significance using a t-statistics and Bonferroni multiple-comparison correction [2].

Our results indicate that unilateral handgrip force control is associated with significant activation clusters at cortical, subcortical, brainstem, cerebellum, C3-C4 cervical spine, and C5-C8 cervical spinal cord (p < 0.05, corrected using GRF) (Fig. 1). We additionally report significant functional connectivity at the C3-C4 cervical level ipsilateral ventral horn with cortical (primary motor and premotor cortex), brainstem (pontine and medullary reticular formation, vestibular nucleus), and cerebellar regions consistent with the propriospinal pathway for hand motor control during the task. Lastly, we observed functional connectivity between the C3-C4 ipsilateral dorsal horn and a subset of cerebellar and cortical regions (p < 0.05, corrected using Bonferroni) (Fig. 2).

Overall, our analysis results in strong activation at the spinal cord and brain during the motor control task. Our main finding suggests propriospinal functional connectivity is critical during hand motor control and is mainly correlated with the ipsilateral ventral horn of the spine and to a lesser degree with the ipsilateral dorsal horn. These methods will be valuable in characterizing the altered descending motor and ascending sensory pathways of stroke patients.

Activation (eg. BOLD task-fMRI)

Connectivity (eg. functional, effective, structural)

fMRI Connectivity and Network Modeling ¹

Motor Planning and Execution ²

BOLD fMRI

Acquisition

Brainstem

Cortex

Data analysis

FUNCTIONAL MRI

Modeling

Motor

MRI

Somatosensory

Spinal Cord