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Reduced short term adaptation to robot generated dynamic environment in children affected by Cerebral Palsy.

Masia L, Frascarelli F, Morasso P, Di Rosa G, Petrarca M, Castelli E, Cappa P - J Neuroeng Rehabil (2011)

Bottom Line: During the FA phase the movements of the CP subjects were more curved, displaying greater and variable directional error; over the course of the CF phase both groups showed a decreasing trend in the lateral error and an after-effect at the beginning of the wash-out, but the CP group had a non significant adaptation rate and a lower learning index, suggesting that CP subjects have reduced ability to learn to compensate external force.Moreover, a directional analysis of trajectories confirms that the control group is able to better predict the force field by tuning the kinematic features of the movements along different directions in order to account for the inertial anisotropy of arm.This lack of information could be related to the congenital nature of the brain damage and may contribute to a better delineation of therapeutic intervention.

View Article: PubMed Central - HTML - PubMed

Affiliation: Robotics Brain and Cognitive Sciences Dept,, Italian Institute of Technology, Genoa, Italy. lorenzo.masia@iit.it

ABSTRACT

Background: It is known that healthy adults can quickly adapt to a novel dynamic environment, generated by a robotic manipulandum as a structured disturbing force field. We suggest that it may be of clinical interest to evaluate to which extent this kind of motor learning capability is impaired in children affected by cerebal palsy.

Methods: We adapted the protocol already used with adults, which employs a velocity dependant viscous field, and compared the performance of a group of subjects affected by Cerebral Palsy (CP group, 7 subjects) with a Control group of unimpaired age-matched children. The protocol included a familiarization phase (FA), during which no force was applied, a force field adaptation phase (CF), and a wash-out phase (WO) in which the field was removed. During the CF phase the field was shut down in a number of randomly selected "catch" trials, which were used in order to evaluate the "learning index" for each single subject and the two groups. Lateral deviation, speed and acceleration peaks and average speed were evaluated for each trajectory; a directional analysis was performed in order to inspect the role of the limb's inertial anisotropy in the different experimental phases.

Results: During the FA phase the movements of the CP subjects were more curved, displaying greater and variable directional error; over the course of the CF phase both groups showed a decreasing trend in the lateral error and an after-effect at the beginning of the wash-out, but the CP group had a non significant adaptation rate and a lower learning index, suggesting that CP subjects have reduced ability to learn to compensate external force. Moreover, a directional analysis of trajectories confirms that the control group is able to better predict the force field by tuning the kinematic features of the movements along different directions in order to account for the inertial anisotropy of arm.

Conclusions: Spatial abnormalities in children affected by cerebral palsy may be related not only to disturbance in motor control signals generating weakness and spasticity, but also to an inefficient control strategy which is not based on a robust knowledge of the dynamical features of their upper limb. This lack of information could be related to the congenital nature of the brain damage and may contribute to a better delineation of therapeutic intervention.

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Learning index for CP and Control groups for 5 different target sets (TS). Each learning index value is computed as the average of eight catch trials, taking into account the corresponding directions, when the force field is active in the CF phase. Solid lines indicate mean value and dashed lines indicate standard error.
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Figure 5: Learning index for CP and Control groups for 5 different target sets (TS). Each learning index value is computed as the average of eight catch trials, taking into account the corresponding directions, when the force field is active in the CF phase. Solid lines indicate mean value and dashed lines indicate standard error.

Mentions: Moreover, a strong indication of the reduced short-term adaptation of the CPs is clearly shown by the learning index (LI) depicted in figure 5. The LI corrects for possible difference in performance due to differences in the action of the force field; if adaptation occurs, during force field the lateral deviation decreases while its value increases for the trajectories performed during catch trials due to the higher compensatory action by the CNS. Figure 5 shows that in the control group LI grows monotonically, in the initial learning, and this behavior is followed by an exponential trend, as expected for a short term adaptation experiment. In contrast, in the CP group LI is characterized by a lower increasing trend, with an early saturation, which implies a reduced learning capability.


Reduced short term adaptation to robot generated dynamic environment in children affected by Cerebral Palsy.

Masia L, Frascarelli F, Morasso P, Di Rosa G, Petrarca M, Castelli E, Cappa P - J Neuroeng Rehabil (2011)

Learning index for CP and Control groups for 5 different target sets (TS). Each learning index value is computed as the average of eight catch trials, taking into account the corresponding directions, when the force field is active in the CF phase. Solid lines indicate mean value and dashed lines indicate standard error.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117777&req=5

Figure 5: Learning index for CP and Control groups for 5 different target sets (TS). Each learning index value is computed as the average of eight catch trials, taking into account the corresponding directions, when the force field is active in the CF phase. Solid lines indicate mean value and dashed lines indicate standard error.
Mentions: Moreover, a strong indication of the reduced short-term adaptation of the CPs is clearly shown by the learning index (LI) depicted in figure 5. The LI corrects for possible difference in performance due to differences in the action of the force field; if adaptation occurs, during force field the lateral deviation decreases while its value increases for the trajectories performed during catch trials due to the higher compensatory action by the CNS. Figure 5 shows that in the control group LI grows monotonically, in the initial learning, and this behavior is followed by an exponential trend, as expected for a short term adaptation experiment. In contrast, in the CP group LI is characterized by a lower increasing trend, with an early saturation, which implies a reduced learning capability.

Bottom Line: During the FA phase the movements of the CP subjects were more curved, displaying greater and variable directional error; over the course of the CF phase both groups showed a decreasing trend in the lateral error and an after-effect at the beginning of the wash-out, but the CP group had a non significant adaptation rate and a lower learning index, suggesting that CP subjects have reduced ability to learn to compensate external force.Moreover, a directional analysis of trajectories confirms that the control group is able to better predict the force field by tuning the kinematic features of the movements along different directions in order to account for the inertial anisotropy of arm.This lack of information could be related to the congenital nature of the brain damage and may contribute to a better delineation of therapeutic intervention.

View Article: PubMed Central - HTML - PubMed

Affiliation: Robotics Brain and Cognitive Sciences Dept,, Italian Institute of Technology, Genoa, Italy. lorenzo.masia@iit.it

ABSTRACT

Background: It is known that healthy adults can quickly adapt to a novel dynamic environment, generated by a robotic manipulandum as a structured disturbing force field. We suggest that it may be of clinical interest to evaluate to which extent this kind of motor learning capability is impaired in children affected by cerebal palsy.

Methods: We adapted the protocol already used with adults, which employs a velocity dependant viscous field, and compared the performance of a group of subjects affected by Cerebral Palsy (CP group, 7 subjects) with a Control group of unimpaired age-matched children. The protocol included a familiarization phase (FA), during which no force was applied, a force field adaptation phase (CF), and a wash-out phase (WO) in which the field was removed. During the CF phase the field was shut down in a number of randomly selected "catch" trials, which were used in order to evaluate the "learning index" for each single subject and the two groups. Lateral deviation, speed and acceleration peaks and average speed were evaluated for each trajectory; a directional analysis was performed in order to inspect the role of the limb's inertial anisotropy in the different experimental phases.

Results: During the FA phase the movements of the CP subjects were more curved, displaying greater and variable directional error; over the course of the CF phase both groups showed a decreasing trend in the lateral error and an after-effect at the beginning of the wash-out, but the CP group had a non significant adaptation rate and a lower learning index, suggesting that CP subjects have reduced ability to learn to compensate external force. Moreover, a directional analysis of trajectories confirms that the control group is able to better predict the force field by tuning the kinematic features of the movements along different directions in order to account for the inertial anisotropy of arm.

Conclusions: Spatial abnormalities in children affected by cerebral palsy may be related not only to disturbance in motor control signals generating weakness and spasticity, but also to an inefficient control strategy which is not based on a robust knowledge of the dynamical features of their upper limb. This lack of information could be related to the congenital nature of the brain damage and may contribute to a better delineation of therapeutic intervention.

Show MeSH
Related in: MedlinePlus