Characterization of age-related modifications of upper limb motor control strategies in a new dynamic environment

Benedetta Cesqui, Giovanna Macrì, Paolo Dario, Silvestro Micera

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Background. In the past, several research groups have shown that when a velocity dependent force field is applied during upper limb movements subjects are able to deal with this external perturbation after some training. This adaptation is achieved by creating a new internal model which is included in the normal unperturbed motor commands to achieve good performance. The efficiency of this motor control mechanism can be compromised by pathological disorders or by muscular-skeletal modifications such as the ones due to the natural aging process. In this respect, the present study aimed at identifying the age-related modifications of upper limb motor control strategies during adaptation and de-adaptation processes in velocity dependent force fields. Methods. Eight young and eight elderly healthy subjects were included in the experiment. Subjects were instructed to perform pointing movements in the horizontal plane both in a null field and in a velocity dependent force field. The evolution of smoothness and hand path were used to characterize the performance of the subjects. Furthermore, the ability of modulating the interactive torque has been used as a paradigm to explain the observed discoordinated patterns during the adaptation process. Results. The evolution of the kinematics during the experiments highlights important behavioural differences between the two groups during the adaptation and de-adaptation processes. In young subjects the improvement of movement smoothness was in accordance with the expected learning trend related to the consolidation of the internal model. On the contrary, elders did not show a coherent learning process. The kinetic analysis pointed out the presence of different strategies for the compensation of the external perturbation: older people required an increased involvement of the shoulder with a different modulation of joint torque components during the evolution of the experiments. Conclusion. The results obtained with the present study seem to confirm the presence of different adaptation mechanisms in young and senior subjects. The strategy adopted by young subjects was to first minimize hand path errors with a secondary process that is consistent with the optimization of the effort. Elderly subjects instead, seemed to shift the importance of the two processes involved in the control loop slowing the mechanism optimizing kinematic performance and enabling more the dynamic adaptation mechanism.

Original languageEnglish
Article number31
JournalJournal of NeuroEngineering and Rehabilitation
Volume5
DOIs
Publication statusPublished - 2008

Fingerprint

Torque
Biomechanical Phenomena
Upper Extremity
Hand
Learning
Aptitude
Healthy Volunteers
Joints
Efficiency
Research

ASJC Scopus subject areas

  • Rehabilitation
  • Health Informatics

Cite this

Characterization of age-related modifications of upper limb motor control strategies in a new dynamic environment. / Cesqui, Benedetta; Macrì, Giovanna; Dario, Paolo; Micera, Silvestro.

In: Journal of NeuroEngineering and Rehabilitation, Vol. 5, 31, 2008.

Research output: Contribution to journalArticle

@article{f26475bdc77f47e3bb7e49cc7453aef2,
title = "Characterization of age-related modifications of upper limb motor control strategies in a new dynamic environment",
abstract = "Background. In the past, several research groups have shown that when a velocity dependent force field is applied during upper limb movements subjects are able to deal with this external perturbation after some training. This adaptation is achieved by creating a new internal model which is included in the normal unperturbed motor commands to achieve good performance. The efficiency of this motor control mechanism can be compromised by pathological disorders or by muscular-skeletal modifications such as the ones due to the natural aging process. In this respect, the present study aimed at identifying the age-related modifications of upper limb motor control strategies during adaptation and de-adaptation processes in velocity dependent force fields. Methods. Eight young and eight elderly healthy subjects were included in the experiment. Subjects were instructed to perform pointing movements in the horizontal plane both in a null field and in a velocity dependent force field. The evolution of smoothness and hand path were used to characterize the performance of the subjects. Furthermore, the ability of modulating the interactive torque has been used as a paradigm to explain the observed discoordinated patterns during the adaptation process. Results. The evolution of the kinematics during the experiments highlights important behavioural differences between the two groups during the adaptation and de-adaptation processes. In young subjects the improvement of movement smoothness was in accordance with the expected learning trend related to the consolidation of the internal model. On the contrary, elders did not show a coherent learning process. The kinetic analysis pointed out the presence of different strategies for the compensation of the external perturbation: older people required an increased involvement of the shoulder with a different modulation of joint torque components during the evolution of the experiments. Conclusion. The results obtained with the present study seem to confirm the presence of different adaptation mechanisms in young and senior subjects. The strategy adopted by young subjects was to first minimize hand path errors with a secondary process that is consistent with the optimization of the effort. Elderly subjects instead, seemed to shift the importance of the two processes involved in the control loop slowing the mechanism optimizing kinematic performance and enabling more the dynamic adaptation mechanism.",
author = "Benedetta Cesqui and Giovanna Macr{\`i} and Paolo Dario and Silvestro Micera",
year = "2008",
doi = "10.1186/1743-0003-5-31",
language = "English",
volume = "5",
journal = "Journal of NeuroEngineering and Rehabilitation",
issn = "1743-0003",
publisher = "BioMed Central",

}

TY - JOUR

T1 - Characterization of age-related modifications of upper limb motor control strategies in a new dynamic environment

AU - Cesqui, Benedetta

AU - Macrì, Giovanna

AU - Dario, Paolo

AU - Micera, Silvestro

PY - 2008

Y1 - 2008

N2 - Background. In the past, several research groups have shown that when a velocity dependent force field is applied during upper limb movements subjects are able to deal with this external perturbation after some training. This adaptation is achieved by creating a new internal model which is included in the normal unperturbed motor commands to achieve good performance. The efficiency of this motor control mechanism can be compromised by pathological disorders or by muscular-skeletal modifications such as the ones due to the natural aging process. In this respect, the present study aimed at identifying the age-related modifications of upper limb motor control strategies during adaptation and de-adaptation processes in velocity dependent force fields. Methods. Eight young and eight elderly healthy subjects were included in the experiment. Subjects were instructed to perform pointing movements in the horizontal plane both in a null field and in a velocity dependent force field. The evolution of smoothness and hand path were used to characterize the performance of the subjects. Furthermore, the ability of modulating the interactive torque has been used as a paradigm to explain the observed discoordinated patterns during the adaptation process. Results. The evolution of the kinematics during the experiments highlights important behavioural differences between the two groups during the adaptation and de-adaptation processes. In young subjects the improvement of movement smoothness was in accordance with the expected learning trend related to the consolidation of the internal model. On the contrary, elders did not show a coherent learning process. The kinetic analysis pointed out the presence of different strategies for the compensation of the external perturbation: older people required an increased involvement of the shoulder with a different modulation of joint torque components during the evolution of the experiments. Conclusion. The results obtained with the present study seem to confirm the presence of different adaptation mechanisms in young and senior subjects. The strategy adopted by young subjects was to first minimize hand path errors with a secondary process that is consistent with the optimization of the effort. Elderly subjects instead, seemed to shift the importance of the two processes involved in the control loop slowing the mechanism optimizing kinematic performance and enabling more the dynamic adaptation mechanism.

AB - Background. In the past, several research groups have shown that when a velocity dependent force field is applied during upper limb movements subjects are able to deal with this external perturbation after some training. This adaptation is achieved by creating a new internal model which is included in the normal unperturbed motor commands to achieve good performance. The efficiency of this motor control mechanism can be compromised by pathological disorders or by muscular-skeletal modifications such as the ones due to the natural aging process. In this respect, the present study aimed at identifying the age-related modifications of upper limb motor control strategies during adaptation and de-adaptation processes in velocity dependent force fields. Methods. Eight young and eight elderly healthy subjects were included in the experiment. Subjects were instructed to perform pointing movements in the horizontal plane both in a null field and in a velocity dependent force field. The evolution of smoothness and hand path were used to characterize the performance of the subjects. Furthermore, the ability of modulating the interactive torque has been used as a paradigm to explain the observed discoordinated patterns during the adaptation process. Results. The evolution of the kinematics during the experiments highlights important behavioural differences between the two groups during the adaptation and de-adaptation processes. In young subjects the improvement of movement smoothness was in accordance with the expected learning trend related to the consolidation of the internal model. On the contrary, elders did not show a coherent learning process. The kinetic analysis pointed out the presence of different strategies for the compensation of the external perturbation: older people required an increased involvement of the shoulder with a different modulation of joint torque components during the evolution of the experiments. Conclusion. The results obtained with the present study seem to confirm the presence of different adaptation mechanisms in young and senior subjects. The strategy adopted by young subjects was to first minimize hand path errors with a secondary process that is consistent with the optimization of the effort. Elderly subjects instead, seemed to shift the importance of the two processes involved in the control loop slowing the mechanism optimizing kinematic performance and enabling more the dynamic adaptation mechanism.

UR - http://www.scopus.com/inward/record.url?scp=57249105453&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=57249105453&partnerID=8YFLogxK

U2 - 10.1186/1743-0003-5-31

DO - 10.1186/1743-0003-5-31

M3 - Article

C2 - 19019228

AN - SCOPUS:57249105453

VL - 5

JO - Journal of NeuroEngineering and Rehabilitation

JF - Journal of NeuroEngineering and Rehabilitation

SN - 1743-0003

M1 - 31

ER -