Background/Aims: Alzheimer's disease (AD) patients have an impaired ability to quickly re-weight ... more Background/Aims: Alzheimer's disease (AD) patients have an impaired ability to quickly re-weight central sensory dependence in response to unexpected body perturbations. Herein, we aim to study provoked compensatory postural adjustments (CPAs) in a conflicting sensory paradigm with unpredictable visual displacements using virtual reality goggles. Methods: We used kinematic time-frequency analyses of two frequency bands: a low-frequency band (LB; 0.3–1.5 Hz; mechanical strategy) and a high-frequency band (HB; 1.5–3.5 Hz; cogni-tive strategy). We enrolled 19 healthy subjects (controls) and 21 AD patients, divided according to their previous history of falls. Results: The AD faller group presented higher-power LB CPAs, reflecting their worse inherent postural stability. The AD patients had a time lag in their HB CPA reaction. Conclusion: The slower reaction by CPA in AD may be a reflection of different cognitive resources including body schema self-perception, visual motion, depth perception , or a different state of fear and/or anxiety.
Background: Postural stability requires the integration of multisensory input information and tra... more Background: Postural stability requires the integration of multisensory input information and translation into appropriate motor responses. Surprisingly, few previous studies have addressed the role of auditory input on postural stability in healthy subjects, and none has investigated this in Alzheimer’s disease (AD). Objective: To assess the influence of the visual and auditory systems on postural stability in patients with AD and healthy subjects. Methods: Twenty-four patients with AD and healthy age-matched subjects were examined by kinematic postural analysis (inertia measurement units placed at the center of mass of the body) under four different conditions: stance with eyes open and eyes closed, with and without suppression of background noise (using ear defenders). The effects of visual and auditory influences were analyzed independently and in conjunction. Results: In both groups, visual suppression had a negative impact on postural stability, while suppression of background noise, non-specifically and without spatial cues, significantly benefited postural stability. We also observed that in both groups, the positive effect of background noise suppression was insufficient to compensate for the negative effect of visual suppression, to which the patients were significantly more vulnerable. Conclusions: Audition, albeit less significant than vision, also plays a role in the multi-sensorial dynamic control of postural stability by the central nervous system. In everyday life, audition is likely to be a relevant factor in postural stability. This is especially relevant in AD in which, even when the peripheral sensory system is intact, the central processing is impaired and sensory dependence is re-weighted.
Postural control is a complex dynamic mechanism, which integrates information from visual, vestib... more Postural control is a complex dynamic mechanism, which integrates information from visual, vestibular and somatosensory systems. Idiopathic Parkinson’s disease (IPD) patients are unable to produce appro- priate reflexive responses to changing environmental conditions. Still, it is controversial what is due to voluntary or involuntary postural control, even less what is the effect of levodopa. We aimed to evalu- ate compensatory postural adjustments (CPA), with kinematic and time-frequency analyzes, and further understand the role of dopaminergic medication on these processes. 19 healthy subjects (Controls) and 15 idiopathic Parkinson’s disease (IPD) patients in the OFF and ON medication states, wearing IMUs, were submitted to a virtual reality scenario with visual downward displacements on a staircase. We also hypothesized if CPA would involve mechanisms occurring in distinct time scales. We subsequently ana- lyzed postural adjustments on two frequency bands: low components between 0.3 and 1.5 Hz (LB), and high components between 1.5 and 3.5 Hz (HB). Vertical acceleration demonstrated a greater power for discriminating IPD patients from healthy subjects. Visual perturbation significantly increased the power of the HB in all groups, being particularly more evident in the OFF state. Levodopa significantly increased their basal power taking place on the LB. However, controls and IPD patients in the ON state revealed a similar trend of the control mechanism. Results indicate an improvement in muscular stiffness provided by levodopa. They also suggest the role of different compensatory postural adjustment patterns, with LB being related to inertial properties of the oscillating mass and HB representing reactions to the ongoing visual input-changing scenario.
Background/Aims: Alzheimer's disease (AD) patients have an impaired ability to quickly re-weight ... more Background/Aims: Alzheimer's disease (AD) patients have an impaired ability to quickly re-weight central sensory dependence in response to unexpected body perturbations. Herein, we aim to study provoked compensatory postural adjustments (CPAs) in a conflicting sensory paradigm with unpredictable visual displacements using virtual reality goggles. Methods: We used kinematic time-frequency analyses of two frequency bands: a low-frequency band (LB; 0.3–1.5 Hz; mechanical strategy) and a high-frequency band (HB; 1.5–3.5 Hz; cogni-tive strategy). We enrolled 19 healthy subjects (controls) and 21 AD patients, divided according to their previous history of falls. Results: The AD faller group presented higher-power LB CPAs, reflecting their worse inherent postural stability. The AD patients had a time lag in their HB CPA reaction. Conclusion: The slower reaction by CPA in AD may be a reflection of different cognitive resources including body schema self-perception, visual motion, depth perception , or a different state of fear and/or anxiety.
Background: Postural stability requires the integration of multisensory input information and tra... more Background: Postural stability requires the integration of multisensory input information and translation into appropriate motor responses. Surprisingly, few previous studies have addressed the role of auditory input on postural stability in healthy subjects, and none has investigated this in Alzheimer’s disease (AD). Objective: To assess the influence of the visual and auditory systems on postural stability in patients with AD and healthy subjects. Methods: Twenty-four patients with AD and healthy age-matched subjects were examined by kinematic postural analysis (inertia measurement units placed at the center of mass of the body) under four different conditions: stance with eyes open and eyes closed, with and without suppression of background noise (using ear defenders). The effects of visual and auditory influences were analyzed independently and in conjunction. Results: In both groups, visual suppression had a negative impact on postural stability, while suppression of background noise, non-specifically and without spatial cues, significantly benefited postural stability. We also observed that in both groups, the positive effect of background noise suppression was insufficient to compensate for the negative effect of visual suppression, to which the patients were significantly more vulnerable. Conclusions: Audition, albeit less significant than vision, also plays a role in the multi-sensorial dynamic control of postural stability by the central nervous system. In everyday life, audition is likely to be a relevant factor in postural stability. This is especially relevant in AD in which, even when the peripheral sensory system is intact, the central processing is impaired and sensory dependence is re-weighted.
Postural control is a complex dynamic mechanism, which integrates information from visual, vestib... more Postural control is a complex dynamic mechanism, which integrates information from visual, vestibular and somatosensory systems. Idiopathic Parkinson’s disease (IPD) patients are unable to produce appro- priate reflexive responses to changing environmental conditions. Still, it is controversial what is due to voluntary or involuntary postural control, even less what is the effect of levodopa. We aimed to evalu- ate compensatory postural adjustments (CPA), with kinematic and time-frequency analyzes, and further understand the role of dopaminergic medication on these processes. 19 healthy subjects (Controls) and 15 idiopathic Parkinson’s disease (IPD) patients in the OFF and ON medication states, wearing IMUs, were submitted to a virtual reality scenario with visual downward displacements on a staircase. We also hypothesized if CPA would involve mechanisms occurring in distinct time scales. We subsequently ana- lyzed postural adjustments on two frequency bands: low components between 0.3 and 1.5 Hz (LB), and high components between 1.5 and 3.5 Hz (HB). Vertical acceleration demonstrated a greater power for discriminating IPD patients from healthy subjects. Visual perturbation significantly increased the power of the HB in all groups, being particularly more evident in the OFF state. Levodopa significantly increased their basal power taking place on the LB. However, controls and IPD patients in the ON state revealed a similar trend of the control mechanism. Results indicate an improvement in muscular stiffness provided by levodopa. They also suggest the role of different compensatory postural adjustment patterns, with LB being related to inertial properties of the oscillating mass and HB representing reactions to the ongoing visual input-changing scenario.
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Papers by Darya Yelshyna
Objective: To assess the influence of the visual and auditory systems on postural stability in patients with AD and healthy subjects.
Methods: Twenty-four patients with AD and healthy age-matched subjects were examined by kinematic postural analysis (inertia measurement units placed at the center of mass of the body) under four different conditions: stance with eyes open and eyes closed, with and without suppression of background noise (using ear defenders). The effects of visual and auditory influences were analyzed independently and in conjunction.
Results: In both groups, visual suppression had a negative impact on postural stability, while suppression of background noise, non-specifically and without spatial cues, significantly benefited postural stability. We also observed that in both groups, the positive effect of background noise suppression was insufficient to compensate for the negative effect of visual suppression, to which the patients were significantly more vulnerable.
Conclusions: Audition, albeit less significant than vision, also plays a role in the multi-sensorial dynamic control of postural stability by the central nervous system. In everyday life, audition is likely to be a relevant factor in postural stability. This is especially relevant in AD in which, even when the peripheral sensory system is intact, the central processing is impaired and sensory dependence is re-weighted.
Objective: To assess the influence of the visual and auditory systems on postural stability in patients with AD and healthy subjects.
Methods: Twenty-four patients with AD and healthy age-matched subjects were examined by kinematic postural analysis (inertia measurement units placed at the center of mass of the body) under four different conditions: stance with eyes open and eyes closed, with and without suppression of background noise (using ear defenders). The effects of visual and auditory influences were analyzed independently and in conjunction.
Results: In both groups, visual suppression had a negative impact on postural stability, while suppression of background noise, non-specifically and without spatial cues, significantly benefited postural stability. We also observed that in both groups, the positive effect of background noise suppression was insufficient to compensate for the negative effect of visual suppression, to which the patients were significantly more vulnerable.
Conclusions: Audition, albeit less significant than vision, also plays a role in the multi-sensorial dynamic control of postural stability by the central nervous system. In everyday life, audition is likely to be a relevant factor in postural stability. This is especially relevant in AD in which, even when the peripheral sensory system is intact, the central processing is impaired and sensory dependence is re-weighted.