D1 and D2 Inhibitions of the Soleus H-Reflex Are Differentially Modulated during Plantarflexion Force and Position Tasks

Author(s)

Magalhaes, Fernando Henrique ^{[1, 2, 3]} ; Elias, Leonardo Abdala ^{[4, 1]} ; da Silva, Cristiano Rocha ^{[1, 2]} ; de Lima, Felipe Fava ^[1] ; de Toledo, Diana Rezende ^[1] ; Kohn, Andre Fabio ^{[1, 2]}

Affiliation

^[1] Univ Sao Paulo, EPUSP, Biomed Engn Lab, Sao Paulo, SP - Brazil

^[2] Univ Sao Paulo, Neurosci Program, Sao Paulo, SP - Brazil

^[3] Univ Sao Paulo, EACH USP, Sch Arts Sci & Humanities, Sao Paulo, SP - Brazil

^[4] Univ Estadual Campinas, Sch Elect & Comp Engn, Dept Biomed Engn, Campinas, SP - Brazil

• Document type: Journal article
• Source: PLoS One; v. 10, n. 11 NOV 24 2015.
• Web of Science Citations: 4

Abstract

Presynaptic inhibition (PSI) has been shown to modulate several neuronal pathways of functional relevance by selectively gating the connections between sensory inputs and spinal motoneurons, thereby regulating the contribution of the stretch reflex circuitry to the ongoing motor activity. In this study, we investigated whether a differential regulation of Ia afferent inflow by PSI may be associated with the performance of two types of plantarflexion sensoriomotor tasks. The subjects (in a seated position) controlled either: 1) the force level exerted by the foot against a rigid restraint (force task, FT); or 2) the angular position of the ankle when sustaining inertial loads (position task, PT) that required the same level of muscle activation observed in FT. Subjects were instructed to maintain their force/position at target levels set at similar to 10% of maximum isometric voluntary contraction for FT and 90 degrees for PT, while visual feedback of the corresponding force/position signals were provided. Unconditioned H-reflexes (i.e. control reflexes) and H-reflexes conditioned by electrical pulses applied to the common peroneal nerve with conditioning-to-test intervals of 21 ms and 100 ms (corresponding to D1 and D2 inhibitions, respectively) were evoked in a random fashion. A significant main effect for the type of the motor task (FT vs PT) (p = 0.005, eta(2)(p) = 0.603) indicated that PTs were undertaken with lower levels of Ia PSI converging onto the soleus motoneuron pool. Additionally, a significant interaction between the type of inhibition (D1 vs D2) and the type of motor task (FT vs PT) (p = 0.038, eta(2)(p) = 0.395) indicated that D1 inhibition was associated with a significant reduction in PSI levels from TF to TP (p = 0.001, eta(2)(p) = 0.731), whereas no significant difference between the tasks was observed for D2 inhibition (p = 0.078, eta(2)(p) = 0.305). These results suggest that D1 and D2 inhibitions of the soleus H-reflex are differentially modulated during the performance of plantarflexion FT and PT. The reduced level of ongoing PSI during PT suggests that, in comparison to FT, there is a larger reliance on inputs from muscle spindles primary afferents when the neuromuscular system is required to maintain position-controlled plantarflexion contractions. (AU)

• FAPESP's process: 13/10433-1 - Discharge properties of motor units from ankle extensor and flexor muscles during sinusoidal modulation of the joint torque and angle
• Grantee: Leonardo Abdala Elias
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/09321-1 - Multivariable study of human postural control in response to haptic cues
• Grantee: Cristiano Rocha da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 11/13222-6 - EVALUATION OF INHIBITORY PATHWAYS AND THE EFFECT OF ELECTRICAL NOISE STIMULATION ON PLANTAR FLEXION NEUROMUSCULAR CONTROL
• Grantee: Fernando Henrique Magalhães
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 11/17193-0 - Behavioral, brain and reflex responses to mechanical and electrical stimuli to study proprioception and the spinal cord in humans
• Grantee: André Fábio Kohn
• Support Opportunities: Regular Research Grants
• FAPESP's process: 13/14667-7 - The influence of task type and intensity of muscle contraction in corticomuscular coherence in the control of ankle joint
• Grantee: Diana Rezende de Toledo
• Support Opportunities: Scholarships in Brazil - Post-Doctoral