Spatiotemporal Maps of Proprioceptive Inputs to the Cervical Spinal Cord During Three-Dimensional Reaching and Grasping

Abstract

Proprioceptive feedback is a critical component of voluntary movement planning and execution. Neuroprosthetic technologies aiming at restoring movement must interact with it to restore accurate motor control. Optimization and design of such technologies depends on the availability of quantitative insights into the neural dynamics of proprioceptive afferents during functional movements. However, recording proprioceptive neural activity during unconstrained movements in clinically relevant animal models presents formidable challenges. In this work, we developed a computational framework to estimate the spatiotemporal patterns of proprioceptive inputs to the cervical spinal cord during three-dimensional arm movements in monkeys. We extended a biomechanical model of the monkey arm with ex-vivo measurements, and combined it with models of mammalian group-Ia, Ib and II afferent fibers. We then used experimental recordings Manuscript

A multimodal approach to capture post-stroke temporal dynamics of recovery

“…The multimodal set-up deployed in this study linked this trend of kinematic improvements to the motoneuronal changes estimated using spinal maps. The use of spinal maps to characterize upper limb movements had so far been limited [33,65,68] and they were never exploited in stroke patients to explore upper limb impairments. Moreover, we recently demonstrated a strong correlation between spinal maps activation and blood-oxygen-level-dependent signal of the spinal cord captured by functional magnetic resonance imaging, which further supports the use of this analysis technique to infer motoneuronal activity [69].…”

Role of Forelimb Morphology in Muscle Sensorimotor Functions During Locomotion in the Cat

“…There is a well-established anatomical organization of motoneuronal pools of forelimb muscles along the rostral-caudal direction of cervical spinal segments with proprioceptive afferents connecting to motoneurons of the parent muscles and, to a lesser extent, their synergists (Sterling and Kuypers, 1967b, a;Fritz et al, 1986a;Fritz et al, 1986b;Levine et al, 2012). This anatomical organization allows for evaluation of spatiotemporal activity of motoneurons during a locomotor cycle based on recorded or computed muscle activity as was done for the lumbar motor pools of locomoting cats (Yakovenko et al, 2002), for the entire spinal cord of humans (Ivanenko et al, 2006) and for proprioceptive inputs to cervical spinal segment during arm reaching and grasping in monkeys (Kibleur et al, 2020).…”

“…Because the cat data were missing for the BB, TLONG, FDS, and EPL MTUs (MTU abbreviations are defined in Fig. 1 and Table 5) in the mentioned studies, we approximated their motor pool localizations using data on arm motor pools in monkeys (Jenny and Inukai, 1983;Kibleur et al, 2020). Since we could not find reliable data on MTUs CB, ANC, EPT, TLAT, TMED, and BR, we approximated their motor pool localizations by the mean values of their synergistic MTUs.…”

“…The resulting proportions of motoneurons for each MTU in each cervical spinal segment are shown in Table 8. Assuming that motoneuronal pools of forelimb muscles and their proprioceptive inputs have the same rostro-caudal spinal distribution (Sterling and Kuypers, 1967b, a;Levine et al, 2012), we computed motor and sensory neuronal activities exiting and entering each spinal segment at each percent of the locomotor cycle as follows (Kibleur et al, 2020):…”