Detection of passive movement in lower limb joints is impaired in individuals with Parkinson's disease.

OBJECTIVE: Sensory information is crucial when performing daily activities, and Parkinson's disease may diminish sensitivity to sensory cues. This study aimed to examine the detection threshold of passive motion of knee and ankle joints in individuals with Parkinson's disease. METHODS: Eighteen individuals in the early stages of idiopathic Parkinson's disease (age: 62.7 ±â€¯7.3 years) and 18 healthy matched controls (age: 62.5 ±â€¯7.1 years) first performed a simple reaction time test. Participants were asked to perform ten trials, during which they had to watch a square on a screen and press a button as quickly as possible when the square lit up. Thereafter, the participants were tested for their detection threshold of passive motion of their lower limb joints. Participants were seated in a specially designed chair and their knee or ankle joint was passively moved at a velocity of 0.5º/s. Participants kept their eyes closed and were instructed to press a button as quickly as possible when any joint motion was detected. RESULTS: Individuals with Parkinson's disease needed more time to perform the reaction time test than did the control participants. Individuals with Parkinson's disease also needed larger angular displacement, even when reaction time was used as a covariate measure, to detect any passive motion, in both knee (0.70ºâ€¯±â€¯0.20º) and ankle (1.03ºâ€¯±â€¯0.23º) joints than did the control participants [(0.57ºâ€¯±â€¯0.20º) and (0.84ºâ€¯±â€¯0.27º), respectively]. CONCLUSION: Impaired joint proprioception can be observed in the early stages of Parkinson's disease, which may compromise the use of proprioception cues from lower limbs.

Parkinson's disease delays predictable visual cue processing without affecting complex and unpredictable visual cue processing in postural control.

This study examined the influence of visual information of different complexities and predictability on the body sway of individuals with Parkinson's disease (PD) during upright stance. Twenty-one individuals at initial stages of PD (62.1 ± 7.2 years), under dopaminergic medication, and 21 controls (62.3 ± 7.1 years) stood inside a moving room, performing 10 trials of 60 s. In the first trial, the room remained motionless. Then, the room oscillated in an anterior-posterior direction. There were three blocks of three trials. In the first block, the room oscillated at 0.2 Hz (periodic simple condition); in the second block, periodic frequencies of 0.1, 0.3, and 0.5 Hz were combined (periodic complex condition); in the third block, non-periodic frequencies of 0.1, 0.3, and 0.5 Hz were combined (non-periodic complex condition). Participants were not informed about the room movement. The displacement of the room and trunk were registered using an OPTOTRAK system. Postural sway was examined using mean sway amplitude, and the relationship between visual information and body sway used coherence, gain, and phase. There was no group difference when the room remained motionless. Upon visual manipulation, the PD group displayed larger sway magnitude in the non-periodic complex condition. Individuals with PD also lagged behind the moving room (lower phase values) compared to controls, only in the periodic simple condition. In the remaining measures, there was no group difference. These results suggest that individuals with PD use complex and unpredictable visual information, similar to controls, during upright stance. However, PD might affect the predictable visual cues processing.

Attentional artifacts in sensorimotor coupling in the postural control of young adults.

Although postural control requires the integration of different sensory cues, little is known about the role of attentional artifacts on the individual's ability to properly respond to postural challenges. This study investigated the effects of concomitant tasks (cognitive and postural) on the relationship between visual information and body sway. Thirty healthy adults were asked to stand still inside of a moving room on normal and reduced bases of support. Initially, the participants were not aware of any visual manipulation and were asked to perform tasks that required concomitant attentional demands. Then, all participants were informed about the visual manipulation and were requested to resist it. The results showed that information about visual manipulation changed the coupling between visual information and body sway, but only in a less demanding task, and that it was affected by the concomitant task. The coupling between visual information and body sway for postural control does not demand attention on a regular basis, but any change in this relationship demands attention and occurs in less demanding postural tasks.