Matti Itkonen

Importance of muscle selection for EMG signal analysis during upper limb rehabilitation of stroke patients

Current work highlights the importance of muscle selection to evaluate paralysis and recovery level of stroke patients when comparing synergies of affected and non-affected side of the body. The proposed method allows the selection of important muscles that highly contribute to the specific movements according to the power and frequency distribution of the electromyographic signals.. Users participating performed steering-wheel-based therapy focused on upper limb rehabilitation. Final results show that with the appropriate muscles selection, it is possible to compute a Similarity Index between right and left arms (during symmetric motion) associated to the level of paralysis and potential recovery of a given subject.

Orchestration of Sensors and Actuators in Neuro-Rehabilitation Experiments and Practice

In traditional rehabilitation a therapist is observing and modifying various kinds of states of a patient. Therefore, to develop a system to help with tasks of therapist, we are facing a complex problem: how to integrate the various devices with diverse inputs and outputs to function as one system? In this paper we represent a systematic approach to build neuro-rehabilitation systems with an integration framework. We discuss a system design issues related to performance and the demanding requirements of rehabilitation. The introduced framework is available for download at: https://github.com/riken-ibcu/bclab.

Tuning of Homologous Muscle Coupling During Bimanual Steering Tasks in Slow Speed: A Pilot Study

Speed control is a crucial factor of motor skill. Although rehabilitation for damaged central mechanisms underpinning the appropriate temporal tuning during bimanual coordination is an important target, the detailed knowledge about the methodology of the therapy is quite limited. This study aimed to clarify the effect of slowing the pace of bimanual rhythmic steering task using a new steering device on the homologous muscle coupling exemplified by the EMG-EMG coherence. At the slow pace, homologous coherence in control subjects at a frequency band of 65–115 Hz in forearm flexors increased relative to the natural speed, whereas small increment in subjects after stroke, suggesting activated central coupling mechanisms dominate the distal muscles for speed adaptation. Relationship between the capability of this mechanism and recovery after stroke is of interesting topic in future studies and will be beneficial for physical rehabilitation.

sEMG Frequency Analysis to Evaluate Changes in the Recruitment of Fast-Twitch Muscles Fibers During Elbow Flexion Motions

An important challenge of stroke rehabilitation consists on the application of efficient therapies during the initial stage of recovery. These strategies should focus on the activation of the local neural loop by reducing those parts of the movement inducing fatigue. Therefore, reducing the recruitment of fast-twitch muscle fibers is an important point while choosing an appropriate therapy. This paper is focus on the evaluation of superficial electromyographic signals during supported and non-supported elbow flexion task to prove their differences in terms of fast-twitch muscle fiber recruitment. To do that, the median frequency extracted from different upper limb muscles of 21 healthy subjects is evaluated showing significant differences supporting authors’ hypothesis.

The Role of Inputs Combination to Enhance the Internal Model and Body Control Ability

The role of attention in formulating the input-signals to the CNS toward enhancing the motor-control ability in human is unclear. Here we hypothesized that the distance between the arms in alignment to the frontal center of a person, and the voluntary shifting of his visual attention play roles in enhancing the internal model and the body-control ability. To examine this, six participants were introduced to dual-steering-device. Using the device, we can modulate the participant’s visual attentions and arms distance while performing various tasks. Major muscles and brain activities of the participants were monitored using EMG, and fNIRS. The results were compatible with our hypothesis: users could inhibit muscular activities in the passive movements with increasing distance of the arms and with a visual focus on the inhibited arm. We believe that this study can add important contributing factors in designing rehabilitation program by adjusting the possible input-combination to enhance the internal-model.

Sensory synergy: Modeling the neural dynamics of environmental feedback to the central nervous system

Human motions are a result of complex-neural interactions between the central nervous system (CNS), sensory and musculoskeletal systems. In this paper, we are focusing in investigating these interactions relying mainly on the concept of sensory- and muscle-synergies. We hypothesize that the CNS is processing and transferring data from sensors and muscles in a unique low-dimensional signaling to simplify the complexity of environmental inputs and to facilitate recruiting muscles patterns. A pilot study involving computing sensory and muscle synergies of seven healthy participants while performing posture balance tasks was conducted to validate our hypotheses. Changes on the participants muscles lengths during performing the task were used to represent proprioceptors and compute sensory synergies. The resultant muscles activities, on the other hand, were recorded and used to estimate muscle synergies. Experimental results suggest that the environmental inputs were translated into lower dimensional signals and used to move the target limb to the desired position immediately after the balance disturbance. Participants who showed better posture response were found to be likely to have a stronger correlation between the utilized sensory and muscle synergies. This preliminary study is considered fundamental to understand the neural strategies among the CNS, sensory and musculoskeletal systems.