Acoplamento visuomotor no controle postural de pessoas com doença de Parkinson

Abstract

Parkinson's disease (PD) causes difficulties in movement control due to changes in motor and sensory systems, and it has been suggested that people with PD show overreliance on vision to control their movements. The aim of this thesis was to investigate the influence of visual information on the postural control performance and on the visuomotor coupling of people with PD compared to those without PD. Therefore, three studies were carried out, with participants standing upright inside a moving room and asked to look at a target on the front wall, during trials of 60 s. In the first study, 14 people with idiopathic PD (69.6 ± 8.8 years, Hoehn & Yahr: 1 to 3) and 14 people with no neurological impairment (control group, 68.6 ± 3.0 years) participated. Each participant performed 10 trials: in the first trial, the room remained motionless and in the others the room was moved in the anteroposterior direction at frequencies of 0.1, 0.17 and 0.5 Hz (three trials at each frequency). A motion analysis system (Optotrak Certus) recorded the movement of the room and the participants’ sway. Postural performance was examined using mean sway amplitude (MSA) and the relationship between visual information and body sway was examined using coherence, gain, phase, position and velocity variability. The people with PD showed larger body sway magnitude than the controls in the conditions when the room remained motionless or was oscillated. Correspondent body sway of people with PD was induced by visual manipulation at all frequencies of the visual stimulus, but their body sway was less coherent compared to the control group. However, no difference was observed in the structure of the visuomotor coupling. In the second study, 21 people with idiopathic PD (62.1 ± 7.2 years, Hoehn & Yahr: 1 and 2) and 21 people in the control group (62.3 ± 7.1 years) participated. Each participant performed 10 trials: in the first trial, the room remained motionless and in the others the room was moved in the anteroposterior direction, in 3 blocks of 3 trials, with different conditions of complexity and predictability of the visual stimulus. In the first block, the room was moved with frequency of 0.2 Hz ("periodic simple" condition); in the second block, the room was moved with combined periodic frequencies of 0.1, 0.3 and 0.5 Hz ("periodic complex" condition); in the third block, the room was moved with combined non-periodic frequencies of 0.1, 0.3 and 0.5 Hz ("non-periodic complex" condition). With no visual manipulation, there was no group difference in MSA. With visual manipulation, the group with PD presented greater sway magnitude only in the non-periodic complex condition. Regarding the relationship between visual information and body sway, people with PD lagged behind the moving room, with larger phase values, compared to their peers, but only in the periodic simple condition. No group difference was found in the remained measurements. In the third study, participants were the same from study 2. Each participant performed 3 blocks of 3 trials, with the room moving at a frequency of 0.2 Hz: in the first block, no information about the room’s movement was given; in the second block, participants were informed about the room’s movement and were asked to resist (do not sway with the room). People with PD presented higher MSA than the control group. In the other measurements, there was no group difference, except in the velocity variability in the condition without information, in which the group with PD presented higher values. In the condition of resisting the visual stimulus, the groups presented lower MSA and lower gain than in the condition with no information. Taken together results from all three studies, it can suggested that people with PD, although presenting a decline in the postural control performance and a delay in the processing of predictable visual information, show no alteration in the visuomotor coupling, regardless of the complexity and predictability of the visual stimulus or the fact that the control was automatic or there was intentional involvement. Therefore, it is concluded that the mechanisms of the central nervous system responsible for the use of visual information for the postural control of people in the early stages of PD are preserved.