Zoekopdracht:
faculteit: "FMG" en publicatiejaar: "1997"
Auteurs  P.C.M. Molenaar, K.M. Newell, S.M. Slobounov, E.S. Slobounova  Titel  Stochastic processes in postural centerofpressure profiles 
Tijdschrift  Experimental Brain Research 
Jaargang  113 
Jaar  1997 
Pagina's  158164 
ISSN  00144819 
Faculteit  Faculteit der Maatschappij en Gedragswetenschappen 
Instituut/afd.  FMG: Psychology Research Institute 
Trefwoorden  Posture; Center of pressure; Stochastic processes; Development 
Samenvatting  The stochastic processes of postural centerofpressure profiles were examined in 3 and 5yearold children, young adult students (mean 20 years), and an elderly age group (mean 67 years). Subjects stood still in an upright bipedal stance on a force platform under vision and nonvision conditions. The time evolutionary properties of the centerofpressure dynamic were examined using basic stochastic process models. The amount of motion of the center of pressure decreased with increments of age from 3 to 5 years to young adult but increased again in the elderly age group. The availability of vision decreased the amount of motion of the center of pressure in all groups except the 3yearold group, where there was less motion of the center of pressure with no vision. The stochastic properties of the centerofpressure dynamic were assessed using both a two process, randomwalk model of Collins and De Luca and an OrnsteinUhlenbeck model that is linear and has displacement governed only by a single stiffness term in the random walk. The twoprocess open and closedloop model accounted for about 96% and the OrnsteinUhlenbeck model 92% of the variance of the diffusion term. Diffusion parameters in both models showed that the data were correlated and that they varied with age in a fashion consistent with developmental accounts of the changing regulation of the degrees of freedom in action. The findings suggest that it is premature to consider the trajectory of the centerofpressure as a twoprocess, open and closedloop randomwalk model given that: (a) the linear OrnsteinUhlenbeck dynamic equation with only two parameters accommodates almost as much of the variance of the random walk; and (b) the linkage of a discontinuity in the diffusion process with the transition of open to closedloop processes is poorly founded. It appears that the nature of the stochastic properties of the random walk of the centerofpressure trajectory in quiet, upright standing remains to be elucidated. 
Soort document  Artikel 
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