Biomedical subjects

Maurizio Schmid

Publications and source records attributed to Maurizio Schmid.

5 recordsLinked to original sources

PubMed2006

Cognitive load affects postural control in children.

Inferring relations between cognitive processes and postural control is a relatively topical challenge in developmental neurology. This study investigated the effect of a concurrent cognitive task on postural control in a sample of 50 nine-year-old children. Each subject completed two balance trials of 60 s, one with a concurrent cognitive task (cognitive load) and another with no cognitive load. The concurrent cognitive task consisted of mentally counting backwards in steps of 2. Twelve posturographic parameters (PPs) were extracted from the centre of pressure (CoP) trajectory obtained through a load cell force plate. Analysis of variance revealed significant differences in the majority of the extracted PPs. CoP was found to travel faster, farther, and with substantially different features demonstrating an overall broadening of the spectrum in the frequency domain. Nonlinear stability factors revealed significant differences when exposed to a concurrent cognitive task, showing an increase of instability in the intervention rate of the postural control system. By grouping children through selected items from Teachers Ratings and PANESS assessment, specific significant differences were also found both in time and frequency domain PPs, thus confirming the hypothesis of an interaction between cognitive processes (and their development), and postural control.

Attention↗

PubMed2006

Difference in sensorimotor adaptation to horizontal and vertical mirror distortions during ballistic arm movements.

When learning a novel motor task, the sensorimotor system must develop new strategies to efficiently control the limb(s) involved, and this adaptation appears to be developed through the construction of a behavioral map known as an 'internal model'. A common method to uncover the mechanisms of adaptation and reorganization processes is to expose the system to new environmental conditions, typically by introducing visual or mechanical distortions. The present study investigated the adaptation mechanisms of the human sensorimotor system to horizontal and vertical mirror distortions (HMD and VMD) during the execution of fast goal-directed arm movements. Mirror distortions (MDs) were created by means of virtual visual feedback on a computer screen while the movement was executed on a graphics tablet. Twenty healthy adult participants were recruited and assigned to one of two groups of 10 people each. Tests were divided in two subsequent blocks of five trials. The first block consisted of trials with no mirror distortion (NMD), while the second block was recorded when exposing one group to HMD and the other to VMD. Both MDs resulted in kinematic changes: during the tests with the MDs the participants did not reach the performance level found at the NMD test. Motor performance during HMD appeared to be globally better than during VMD and the adaptation process to VMD appeared to be slower than to HMD, but data interpretation was hampered by large within-participant and between-participant variability. In-depth analyses of the data revealed that most of the motor performance information was contained in the direction of movement. The data supported the idea that the internal model for HMD was already partially built.

Adult↗

PubMed2005

A markerless sub-pixel motion estimation technique to reconstruct kinematics and estimate the centre of mass in posturography.

A novel method to evaluate postural sway is presented: balance strategies are identified by applying a markerless image processing algorithm to video sequences obtained from commercially available systems. The motion estimation technique for the analysis of video sequences is a coarse to fine procedure based on the block matching algorithm (BMA). The method makes it possible to estimate the movement of selected elements on the scene with a sub-pixel precision. It has been done by applying a bicubic spline interpolation to the coarse results obtained by the BMA. Results achieved through the analysis of synthetic video tests make it possible to determine the accuracy of the proposed sub-pixel algorithm. Figures show how the proposed method can be confidently applied to evaluate postural sway. The proposed method has been applied to videos recorded during orthostatic posture trials in different conditions, and to combined tests where signals from a balance plate have been acquired simultaneously to the video sequence. The results show the usefulness of the proposed approach in order to evaluate balance strategies in posturography.

Algorithms↗

PubMed2005

The development of postural strategies in children: a factorial design study.

BACKGROUND: The present study investigates balance control mechanisms, their variations with the absence of visual input, and their development in children from 7 to 11 years old, in order to provide insights on the development of balance control in the pediatric population. METHODS: Posturographic data were recorded during 60 s trials administered on a sample population of 148 primary school children while stepping and then quietly standing on a force plate in two different vision conditions: eyes closed and eyes open. The extraction of posturographic parameters on the quiet standing phase of the experiment was preceded by the implementation of an algorithm to identify the settling time after stepping on the force plate. The effect of different conditions on posturographic parameters was tested with a two-way ANOVA (Age x Vision), and the corresponding eyes-closed/eyes-open (Romberg) Ratios underwent a one-way ANOVA. RESULTS: Several posturographic measures were found to be sensitive to testing condition (eyes closed vs. eyes open) and some of them to age and anthropometric parameters. The latter relationship did not explain all the data variability with age. An evident modification of postural strategy was observed between 7 and 11 years old children. CONCLUSION: Simple measures extracted from posturographic signals resulted sensitive to vision and age: data acquired from force plate made it possible to confirm the hypothesis of the development of postural strategies in children as a more mature selection and re-weighting of proprioceptive inputs to postural control in absence of visual input.

Journal Article↗

PubMed2004

Respiration and postural sway: detection of phase synchronizations and interactions.

The aim of the central nervous system in upright stance is to control an intrinsically unstable plant. Internal disturbances, such as haemodynamics and respiration, constitute an endogenous threat to equilibrium. The way CNS reacts to those perturbations was studied in this work, through the analysis of summary scores taken from posturographic and pneumographic data. Signals were recorded simultaneously during trials administered on a sample population of healthy young adults, while sitting and standing and at paced and spontaneous uncontrolled breathing. The extraction of posturographic and pneumographic parameters was accompanied by the utilization of techniques for the detection of phase synchronization in bivariate data, and the extraction of an interaction index, the mutual information MI. The effects of the biomechanical condition and respiratory amplitude on MI and summary measures were tested with a two-way ANOVA. Summary scores clearly depend on posture condition. Synchronization between breath and postural sway is always present, depends on both biomechanical condition and respiratory threat, and cannot be reduced to a simple linear relation.

Adult↗