Flexibility of anticipatory postural adjustments revealed by self-paced and reaction-time arm movements

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104

Klous M, Mikulic P, Latash ML. Two aspects of feedforward postural control: anticipatory postural adjustments and anticipatory synergy adjustments. J Neurophysiol 105: 2275-2288, 2011. First published March 9, 2011 doi:10.1152/jn.00665.2010.-We used the framework of the uncontrolled manifold hypothesis to explore the relations between anticipatory synergy adjustments (ASAs) and anticipatory postural adjustments (APAs) during feedforward control of vertical posture. ASAs represent a drop in the index of a multimusclemode synergy stabilizing the coordinate of the center of pressure in preparation to an action. ASAs reflect early changes of an index of covariation among variables reflecting muscle activation, whereas APAs reflect early changes in muscle activation levels averaged across trials. The assumed purpose of ASAs is to modify stability of performance variables, whereas the purpose of APAs is to change magnitudes of those variables. We hypothesized that ASAs would be seen before APAs and that this finding would be consistent with regard to the muscle-mode composition defined on the basis of different tasks and phases of action. Subjects performed a voluntary body sway task and a quick, bilateral shoulder flexion task under self-paced and reaction time conditions. Surface muscle activity of 12 leg and trunk muscles was analyzed to identify sets of 4 muscle modes for each task and for different phases within the shoulder flexion task. Variance components in the muscle-mode space and indexes of multimuscle-mode synergy stabilizing shift of the center of pressure were computed. ASAs were seen ϳ100 -150 ms prior to the task initiation, before APAs. The results were consistent with respect to different sets of muscle modes defined over the two tasks and different shoulder flexion phases. We conclude that the preparation for a self-triggered postural perturbation is associated with two types of anticipatory adjustments, ASAs and APAs. They reflect different feedforward processes within the hypothetical hierarchical control scheme, resulting in changes in patterns of covariation of elemental variables and in their patterns averaged across trials, respectively. The results show that synergies quantified using dissimilar sets of muscle modes show similar feedforward changes in preparation to action. uncontrolled manifold hypothesis DURING STANDING, the human body is inherently unstable because of the small support area, high center of mass, and multijoint design. Voluntary movements performed by a standing person contribute to problems of postural control by producing postural perturbations because of the mechanical coupling of the body segments. When a standing person performs a fast arm movement, changes in the activation of postural muscles are typically seen about 100 ms before movement initiation; these changes have been addressed as anticipatory postural adjustments (APAs; reviewed in Massion 1992). The role of APAs has been assumed to produce joint torques and forces that minimize perturbation of the vertical...

Section: Two Aspects Of Feedforward Control Of Posturesupporting

confidence: 88%

Two aspects of feedforward postural control: anticipatory postural adjustments and anticipatory synergy adjustments

Klous

Mikulić

Latash

2011

110

104

“…Second, APAs are reportedly modulated by CoP position before voluntary movement (Benvenuti et al 1997;Fujiwara et al 2003). In the present study, the initial CoPy position was significantly more anterior in the SDCP group than in the control group, suggesting a larger stability margin in the backward direction in the participants with SDCP.…”

Section: Discussionsupporting

confidence: 39%

“…a, Metal frame; b, infrared camera; c, metal wires; d, accelerometer; e, load; f, surface electrode; g, reflective marker; h, force platform. (Benvenuti et al 1997;Fujiwara et al 2003). To minimize intertrial differences in APAs due to differences in CoP position before the load release, a buzzing sound, which was generated by a computer (PP21L, Dell, Round Rock, TX) connected to the force platform, was used to inform participants if they were maintaining CoPx and CoPy positions within a range of Ϯ1.5 cm of the quiet standing position.…”

Section: Methodsmentioning

confidence: 99%

Deficits in anticipatory inhibition of postural muscle activity associated with load release while standing in individuals with spastic diplegic cerebral palsy

Tomita

Fukaya²,

Totsuka

et al. 2013

“…This further supports the idea that the strategy adopted by the cat is controlled by 2 distinct descending signals, one signal triggered by the stimulus and the other, later signal providing the detailed information about the movement to be made. Unfortunately, the current data set does not allow us to determine to what extent the postural responses are tailored to the details of the movement to be made (see, e.g., Benvenuti et al 1997;Bouisset et al 2000). Given the debate we raised in the previous section concerning what constitutes the onset of movement, we would emphasize that our conclusions hold regardless of whether one considers maxlFL V or lift to represent movement initiation.…”

Section: Integration Between Posture and Movementmentioning

confidence: 84%

“…Although there are data from human studies to suggest that the APAs and the focal movement may be independently controlled (Benvenuti et al 1997;de Wolf et al 1998;Massion 1992), there is insufficient evidence to determine the nature of the relationship between the APAs and the focal movement during voluntary limb movements in the quadruped. Obtaining such information is critical to future experiments designed to determine the relative contribution of different neural structures to the control of these 2 aspects of motor control.…”

Section: Introductionmentioning

confidence: 99%

Strategies for the Integration of Posture and Movement During Reaching in the Cat

Schepens

Drew

2003

We have examined the relationship between the movement and the anticipatory postural adjustments (APAs) that precede that movement during a reaching task in the cat. We recorded ground reaction forces in all 3 planes from all 4 limbs as well as electromyographic (EMG) activity from limb and axial muscles. The reaching movement was always preceded by an APA that was characterized by a loading of the reaching forelimb and an unloading of the support forelimb. This loading of the reaching forelimb was preceded, and accompanied, by increased activity in shoulder and limb extensor muscles of the reaching limb; extensor muscle activity in the supporting limb was simultaneously decreased. An important finding from this study was that the onset of the APA and of the movement was temporally decoupled. Analyses of the onset of EMG activity showed that most of the muscles that we recorded could be classified as either related to the APA or related to the movement. These results support the idea of distributed, and perhaps independent, systems for the execution of the APA and of the prime movement. There was also postural activity in the supporting limb during the movement. Analysis of this activity, which is also anticipatory in nature, suggests that it was tightly linked to the movement. We suggest that this postural response is signaled as part of the command for movement. Some muscles, particularly the extensors of the reaching limb, received convergent input from the command signals for the APA and for the movement.