Proprioceptive reaction times and long-latency reflexes in humans

• Published in: Experimental brain research Vol. 221; no. 2; pp. 155 - 166
• Main Authors: Manning, C. D., Tolhurst, S. A., Bawa, P.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.08.2012; Springer; Springer Nature B.V
• Subjects: Adult; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Choice Behavior; Data processing; Ear and associated structures. Auditory pathways and centers. Hearing. Vocal organ. Phonation. Sound production. Echolocation; Electromyography; EMG; Evoked Potentials, Motor - physiology; Female; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Humans; Limbs; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Movement - physiology; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Muscles; Neurology; Neurosciences; Physical Stimulation; Proprioception; Proprioception - physiology; Reaction Time - physiology; Reaction time task; Reflex - physiology; Reflexes; Research Article; Skin - innervation; Time Factors; Torque; Upper Extremity - physiology; Vertebrates: nervous system and sense organs; Wrist; Young Adult; Transcortical reflex; Reaction time; Gain modulation; Prior instruction; Reflex gain; Human; Reflex; Proprioception; Electrophysiology; Perturbation; Instruction; Wrist; Modulation; Electromyography; Upper limb; Muscle
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-012-3157-x

The stretch of upper limb muscles results in two electromyographic (EMG) peaks, M1 and M2. The amplitude of M2 peak can generally be modified by giving prior instruction to the subject on how to react to the applied perturbation. The unresolved question is whether the amplitude modulation results from change in the gain of the reflex pathway contributing to M2, or by superposition of reaction time (RT) activity. The following study attempted to resolve this question by examining the overlap between proprioceptive RT and M2 activities. Subject’s right wrist flexors were stretched, and he/she was instructed either (1) not to intervene (passive task) or (2) to react as fast as possible by simultaneously flexing both wrists (active or compensate task). Under passive and active conditions, M1 and M2 were observed from EMG of right wrist flexors, and during the active condition, RT activities were additionally observed from both sides. The onset and offset of M2 (M1 onset , M2 offset ) were measured from the passive averages, while the RT was measured from the averaged EMG response of the left wrist flexors. For between-subject correlations, the data were divided into two sets: (1) subjects with RT shorter than M2 offset (fast group) and (2) subjects with RT more than 10 ms longer than their M2 offset (slow group). Modulation during M2 period was large for the fast group, and it was almost zero for the slow group. These results indicate that the superimposition of RT activity mainly contributes to the instruction-dependent modulation of M2 peak.