Association between activity in the ventral premotor cortex and spinal cord activation during force generation—A combined cortico‐spinal fMRI study

Abstract

Force generation is a crucial element of dexterity and a highly relevant skill of the human motor system. How cerebral and spinal components interact and how spinal activation is associated with the activity in the cerebral primary motor and premotor areas is poorly understood. Here, we conducted combined cortico‐spinal functional magnetic resonance imaging during a simple visually guided isometric force generation task in 20 healthy young subjects. Activation was localized in the right cervical spinal cord and left primary motor and premotor areas. The main finding is that spinal activation was negatively correlated with ventral premotor cortex activation. Spinal activation was furthermore significantly correlated with primary motor cortex activation, while increasing target forces led to an increase in the amount of activation. These data indicate that human premotor areas such as the ventral premotor cortex might be functionally connected to the lower cervical spinal cord contributing to distal upper limb functions, a finding that extends our understanding of human motor function beyond the animal literature.

FASB: an integrated processing pipeline for Functional Analysis of simultaneous Spinal cord-Brain fMRI

“…The force control task was selected due to 3 main advantages compared to similar motor tasks performed in the scanner: 1) The task is isometric, so there is no difference in movement kinematics across participants, 2) The produced force is normalized across individuals using their MVC, and 3) The isometric task minimizes motion artifacts, which are critical for spinal cord imaging at the neck level. The activated cortical and subcortical areas during this task are consistent with our previous fMRI studies using hand movements (Braaß et al, 2023;Vahdat et al, 2017Vahdat et al, , 2015Vahdat et al, , 2011, including contralateral M1, S1, premotor cortex, SII, PPC, thalamus, striatum, SMA, and ipsilateral cerebellum (Fig. 7).…”

Altered functional connectivity between cortical premotor areas and the spinal cord in chronic stroke

“…A simple motor task was used comprising repetitive whole-hand grips in a block design as previously introduced in detail 41 . In three active conditions, stroke patients performed repetitive visually guided, almost isometric whole-hand grips with their affected hand with three varying predefined force levels (low, medium, and high corresponding to 30%, 50%, and 70% of the maximum output measurement) using an MRI compatible grip force response device (Grip Force Bimanual, Current Design, Inc, Philadelphia, PA).…”

“…A 3T Prisma MRI scanner (Siemens Healthineers, Erlangen, Germany) and a 64-channel combined head-neck coil were used to acquire cerebral and spinal imaging data. The MRI protocol was identical to the previously described MRI protocol 41 . The imaging modalities included high-resolution T1, T2*-weighted, and task-related fMRI images with the iso-center approximately centered to vertebral level C2/C3.…”

“…In the motor domain, studies have just started to explore corticospinal functional connectivity during finger or hand movements in healthy participants 35,[39][40][41] . In our previous study we were able to link ventral spinal activation during simple hand movements not only to M1 activation, but also PMV activation 41 . This added first fMRI data to sparse transcranial magnetic stimulation data [42][43][44] which had suggested that human premotor areas might be functionally connected to the lower cervical spinal cord, likely interneurons, and contribute to distal upper limb functions in humans.…”

Cerebro-spinal somatotopic organization uncovered through functional connectivity mapping

“…Only very recently, advances in fMRI have enabled the simultaneous investigation of both brain and spinal cord functional activity across the sensorimotor hierarchy (see Kaptan et al 2024; Tinnermann et al 2021a for reviews). Despite the potential of cerebro-spinal fMRI, the literature on this topic remains sparse, with most studies focusing on pain (Sprenger et al 2015, 2018; Oliva et al 2022; Tinnermann et al 2017, 2021b, 2022) and a limited number on motor tasks (Vahdat et al 2015; Khatibi et al 2022; Braaß et al2023; Kinany et al 2023b). To the best of our knowledge, only one study has deployed simultaneous cerebro-spinal fMRI to investigate the large-scale functional organization of brain and spinal cord activity, using resting-state recordings (Vahdat et al, 2020).…”