Time and direction preparation of the long latency stretch reflex

• Published in: Human movement science Vol. 47; pp. 38 - 48
• Main Authors: Nikaido, Yasutaka, Hatanaka, Ryota, Jono, Yasutomo, Nomura, Yoshifumi, Tani, Keisuke, Chujo, Yuta, Hiraoka, Koichi
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2016
• Subjects: Adult; Afferent Pathways; Electromyography; Female; Fingers - physiology; First dorsal interosseous muscle; Force load; Humans; Long latency stretch reflex; Male; Muscle, Skeletal - physiology; Perturbation; Prediction; Reflex, Stretch - physiology; Time Factors; Young Adult; Perturbation; Force load; First dorsal interosseous muscle; Long latency stretch reflex; Prediction
• ISSN: 0167-9457; 1872-7646
• DOI: 10.1016/j.humov.2016.01.016

•Time preparation enhances long latency motor response.•Enhancement of motor response by time preparation is not mediated by muscle stretch afferents.•Long latency motor response is partially mediated by direction-insensitive sensations.•Preparation of response to muscle stretch occurs through preset of the afferent pathway. This study investigated time and direction preparation of motor response to force load while intending to maintain the finger at the initial neutral position. Force load extending or flexing the index finger was given while healthy humans intended to maintain the index finger at the initial neutral position. Electromyographic activity was recorded from the first dorsal interosseous muscle. A precue with or without advanced information regarding the direction of the forthcoming force load was given 1000ms before force load. Trials without the precue were inserted between the precued trials. A long latency stretch reflex was elicited by force load regardless of its direction, indicating that the long latency stretch reflex is elicited not only by muscle stretch afferents, but also by direction-insensitive sensations. Time preparation of motor response to either direction of force load enhanced the long latency stretch reflex, indicating that time preparation is not mediated by afferent discharge of muscle stretch. Direction preparation enhanced the long latency stretch reflex and increased corticospinal excitability 0–20ms after force load when force load was given in the direction stretching the muscle. These enhancements must be induced by preset of the afferent pathway mediating segmental stretch reflex.