Software
NMClab
Schouten AC, Mugge W, van der Helm FCT. NMClab, a model to assess the contributions of muscle visco-elasticity and afferent feedback to joint dynamics. Journal of Biomechanics 41 (2008) 1659–1667.
The dynamic behavior of a neuromusculoskeletal system results from the complex mechanical interaction between muscle viscoelasticity resulting from (co-)contraction and afferent feedback from muscle spindles and Golgi tendon organs. As a result of the multiple interactions the individual effect of each of the structures to the overall dynamics is hard to recognize, if not impossible. NMClab is a neuromuscular control (NMC) model developed to analyze the functional contribution of the various physiological structures on the mechanical behavior of a limb. The dynamics of a joint are presented in admittances, i.e. the dynamic relation between input force (or torque) and the output displacement, which can be represented by either frequency or impulse response functions.
The presented model is made freely available in software allowing users to explore the interactions through an intuitive, easily interpretable, graphical user interface.
M1M2 Model
Schuurmans J, De Vlugt E, Schouten AC, Meskers GM, De Groot JH, Van der Helm FCT. The monosynaptic Ia afferent pathway can largely explain the stretch duration effect of the long latency M2 response. Experimental Brain Research (2009) 192:491-500.
Sudden stretch of active muscle typically results in two characteristic electromyographic responses: the short latency M1 and the long latency M2. The M1 response originates from the monosynaptic Ia afferent reflex pathway. The M2 response is less well understood and is likely a compound response to different afferent inputs mediated by spinal and transcortical pathways. In this study the possible contribution of the Ia afferent pathway to the M2 response was investigated. A mechanism was hypothesized in which the M1 response synchronizes the motoneurons, and therewith their refractory periods. Stretch perturbation experiments were performed on the wrist and results were compared with a computational model of a pool of motoneurons receiving tonic and Ia afferent input. The simulations showed the same stretch amplitude, velocity, and duration-dependent characteristics on the M2 as found experimentally. It was concluded that the stretch duration effect of the M2 likely originates from the proposed Ia afferent mediated mechanism.
The model used in this study is made freely available for download. Minimal system requirements: Matlab 2007b or higher.
MVS
Forbes PA, Dakin CJ, Geers AM, Vlaar MP, Happee R, Siegmund GP, Schouten AC, Blouin JS. Electrical vestibular stimuli to enhance vestibulo-motor output and improve subject comfort. PLoS ONE (2013)
Electrical vestibular stimulation is often used to assess vestibulo-motor and postural responses in both clinical and research settings. Stochastic vestibular stimulation (SVS) is a recently established technique with many advantages over its square-wave counterpart; however, the evoked muscle responses remain relatively small. Although the vestibular-evoked responses can be enhanced by increasing the stimulus amplitude, subjects often perceive these higher intensity electrical stimuli as noxious or painful. Here, we developed multisine vestibular stimulation (MVS) signals that include precise frequency contributions to increase signal-to-noise ratios (SNR) of stimulus-evoked muscle and motor responses. Subjects were exposed to three different MVS stimuli to establish that: 1) MVS signals evoke equivalent vestibulo-motor responses compared to SVS while improving subject comfort and reducing experimentation time, 2) stimulus-evoked vestibulo-motor responses are reliably estimated as a linear system and 3) specific components of the cumulant density time domain vestibulo-motor responses can be targeted by controlling the frequency content of the input stimulus. The enhanced vestibulo-motor output responses and improved subject comfort provided by MVS signals should prove beneficial for both research and clinical applications.
The signals and scripts used in this study are made freely available for download.
Download the signals in Matlab (Supporting_Information_S1.zip)