Goal-dependent modulation of the long-latency stretch response at the shoulder, elbow, and wrist

Abstract

Weiler J, Gribble PL, Pruszynski JA. Goal-dependent modulation of the long-latency stretch response at the shoulder, elbow, and wrist. J Neurophysiol 114: 3242-3254, 2015. First published October 7, 2015 doi:10.1152/jn.00702.2015.-Many studies have demonstrated that muscle activity 50 -100 ms after a mechanical perturbation (i.e., the long-latency stretch response) can be modulated in a manner that reflects voluntary motor control. These previous studies typically assessed modulation of the long-latency stretch response from individual muscles rather than how this response is concurrently modulated across multiple muscles. Here we investigated such concurrent modulation by having participants execute goal-directed reaches to visual targets after mechanical perturbations of the shoulder, elbow, or wrist while measuring activity from six muscles that articulate these joints. We found that shoulder, elbow, and wrist muscles displayed goal-dependent modulation of the long-latency stretch response, that the relative magnitude of participants' goal-dependent activity was similar across muscles, that the temporal onset of goal-dependent muscle activity was not reliably different across the three joints, and that shoulder muscles displayed goal-dependent activity appropriate for counteracting intersegmental dynamics. We also observed that the long-latency stretch response of wrist muscles displayed goal-dependent modulation after elbow perturbations and that the long-latency stretch response of elbow muscles displayed goal-dependent modulation after wrist perturbations. This pattern likely arises because motion at either joint could bring the hand to the visual target and suggests that the nervous system rapidly exploits such simple kinematic redundancy when processing sensory feedback to support goal-directed actions.

The primary afferent activity cannot capture the dynamical features of muscle activity during reaching movements

“…This information could be used for estimating limb state with the internal forward model possibly located in the cerebellum, as suggested by observations that cerebellar neuronal activity is related to arm movement kinematics (Casabona et al, 2004;Pasalar et al, 2006). The transformations required to convert sensory feedback into motor commands appropriate for the compensation for limb dynamics appear to occur at the supraspinal levels of the CNS, as evidenced by the scaling of long-latency, but not short-latency, stretch reflexes together with mechanical interactions between arm joints in humans (Kurtzer et al, 2009;Weiler et al, 2015). A control schema for sensorimotor transformation with hybrid forward/inverse models has been proposed .…”

Spinal stretch reflexes support efficient control of reaching

“…Participants grasped the handle of a three degree-of-freedom exoskeleton robot (Interactive Motion Technologies), which allows movement of the hand in a horizontal plane by flexing or extending the shoulder, elbow and wrist (Weiler et al, 2015). The exoskeleton is equipped with direct-drive motors (risetime = 2ms) that can independently apply flexion or extension torques at each of the aforementioned joint segments, and with 16-bit rotary encoders (Gurley Precision Instruments) to measure joint kinematics (resolution = 0.0055 degrees).…”

Task‐dependent responses to muscle vibration during reaching

“…We used the onset detection method by Weiler et al. () and restricted it to consider only deviations in the direction of the observed group mean effects (see Results). To determine the onset times of responses to vibration, we entered the lateral forces of null trials versus trials with muscle vibration (biceps or triceps), separately for each target.…”

“…The envelope of the band-passed force measurement was determined using the absolute of its Hilbert transform. For detecting the onset delay of a vibrator on a specific muscle, we used the method from Weiler et al (2015) and entered the pooled envelope traces from all participants' null trials and the pooled envelope traces with biceps or triceps vibration, respectively. The search range for the delay was restricted between 100 and 200 ms after reach onset.…”

“…To estimate the onset times of subjects' reactions, we used the conditions with compensation to vibration consistent with an illusory lengthening of the vibrated muscle, that is, biceps vibration for reaches away and triceps vibration for reaches toward the subject (see Results). We used the onset detection method by Weiler et al (2015) and restricted it to consider only deviations in the direction of the observed group mean effects (see Results). To determine the onset times of responses to vibration, we entered the lateral forces of null trials versus trials with muscle vibration (biceps or triceps), separately for each target.…”