Exoskeleton and Brain Activity With fNIRS
Condition: Healthy; Gait Disorders, Neurologic
MeSH terms: Nervous System Diseases; Gait Disorders, Neurologic
Study type: Interventional

Summary: 
      Background. Force control is one of the major parameter of motor activity. There is few study
      concerning the cortical activity imply for different levels of force during gait.

      Objective. To investigate cortex activation while walking an exoskeleton with 4 levels of
      guidance force in healthy controls.

      Methods. The investigators acquired near-infrared spectroscopy (fNIRS) with a 20 channels
      device (Brite 24® ; Artinis) covering bilaterally most motor control brain regions during
      exoskeleton walking at different level of force (100 %, 50% aid, 0 % aid and 25 % of
      resistance) in 24 healthy controls. The investigators measured variations of oxyhemoglobin
      (HbO2) and deoxyhemoglobin (HbR). The technique was optimized by the use of reference
      channels (to correct for superficial hemodynamic interference).
    

Detailed description: 
      An important goal of motor systems neuroscience is to characterize how neural activity in the
      brain mediates movement parameters such as force, velocity, frequency of movement or movement
      direction. The neural codage of force has been studied in animal and human with TEP , fMRI ,
      functional near-infrared spectroscopy (fNIRS), EEG or magnetic stimulation.

      Electrophysiological studies in nonhuman primates demonstrated a correlation between neuronal
      discharge rates in multiple regions of the contralateral motor cortex and exerted force
      amplitude .

      In humans, functional magnetic resonance imaging (fMRI) studies confirmed the relation
      between increasing neuronal activation and increasing amplitude of force in the contralateral
      primary motor/somatosensory (M1/S1) cortices, supplementary motor area (SMA), and premotor
      cortex. The ipsilateral motor cortex could also contribute to the force codage. There are
      also evidences that the basal ganglia-thalamo-cortical loop participates to the regulation of
      force control. The internal portion of the globus pallidus (GPi) and subthalamic nucleus
      (STN) had a positive increase in percent signal change with increasing force, and the ventral
      thalamic regions were also implied in the the same way. More recently, studies with fNIRS
      confirmed the relationship between force level and cerebral activation in contralateral and
      ipsilateral hemisphere.

      Most of the human studies concerned isometric static tasks. Only few studies considered
      dynamic movements. As a rule, the processing of repetitive transient force changes requires
      more metabolic activity than the generation and control of a static force. There is a
      correlation between the force level and cortical changes within the neuronal network in
      contralateral M1 and anterior cerebellum.

      Most of the studies concern the upper limb. To our knowledge only to studied concern the
      lower limb in an isometric force level. One concerns the neural correlates of quadriceps
      torque control in chronic obstructive pulmonary disease patients and the other one concerns
      isometric contractions with the ankle dorsiflexor in healthy controls.

      fMRI and TEP are highly sensitive to motion artifacts and not suitable for dynamic proximal
      joints or gait studies. fNIRS is less sensitive to motion artifacts and has permitted
      numerous studies of walking under more natural conditions in controls or patients. fMRI and
      fNIRS are based on the physiological principles of neurovascular coupling, the process by
      which active brain regions induce a local increase in blood flow to match their energy
      demands via the dilation of capillaries and arterioles. fMRI measures the blood oxygen
      level-dependent (BOLD) response corresponding to the ratio of oxy to deoxy-hemoglobin.
      However, the two moieties of hemoglobin are not individually measured with fMRI. On the
      contrary, fNIRS measures the two hemoglobin species separately. During this neurovascular
      coupling, the amount of oxygen supplied is typically greater than that consumed locally,
      resulting in a substantial increase in HbO2 and a slight reduction in HbR in the region.

      Many of the fNIRS studies about gait recorded hemodynamic variations in the prefrontal cortex
      with dual tasks paradigm. Only few studies concerned the motor cortex.

      In recent years, robot-assisted rehabilitation has been used in addition to conventional
      rehabilitation. It offers opportunities for early, intensive, task-specific management with
      multi-sensory stimulation that is considered the most efficient for promoting
      neuroplasticity. Literature suggests that robotic rehabilitation increases the walking
      ability of patients , walking speed , lower limb muscle strength, step length and walking
      symmetry . However, the neurophysiological bases of robot-assisted rehabilitation remain
      poorly known. The use of an exoskeleton makes it possible to control the percentage of aid
      provided. In this study in healthy subjects the investigators propose to study brain
      activation in motor regions when walking in an exoskeleton. Four strength levels are studied:
      total aid (A100%), partial help (A50%), no help (A0%) and resistance of 25 % (R25%) to
      walking from the exoskeleton. The investigators hypothesize that the level of brain
      activation measured by fNIRS will increase with the effort provided by the subjects.
    

Intervention name(s): walking in 4 situations
Intervention type(s): Other
Intervention description(s): Recording of cerebral hemodynamic with fNIRS during gait in exoskeleton with Four strength levels of aid : total aid (A100%), partial aid (A50%), no aid (A0%) and resistance of 25 % (R25%) to walking from the exoskeleton. Each subject are recorded during 8 trials for each level (32 trials). The order is counterbalanced among the subjects
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Health Services Research
Keywords: fNIRS; Motor cortex activity; Gait; Effort; exoskeleton