People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive d... more People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive domains that interact with mobility. Specifically, freezing of gait is associated with executive dysfunction involving response inhibition, divided attention or switching attention, and visuospatial function. The neural control impairments leading to freezing of gait have recently been attributed to higher-level, executive and attentional cortical processes involved in coordinating posture and gait rather than to lower-level, sensorimotor impairments. To date, rehabilitation for freezing of gait primarily has focused on compensatory mobility training to overcome freezing events, such as sensory cueing and voluntary step planning. Recently, a few interventions have focused on restitutive, rather than compensatory, therapy. Given the documented impairments in executive function specific to patients with PD who freeze and increasing evidence of overlap between cognitive and motor function, incorporating cognitive challenges with mobility training may have important benefits for patients with freezing of gait. Thus, a novel theoretical framework is proposed for exercise interventions that jointly address both the specific cognitive and mobility challenges of people with PD who freeze.
Protective postural responses to external perturbations are hypokinetic in people with Parkinson&... more Protective postural responses to external perturbations are hypokinetic in people with Parkinson's disease (PD), and improving these responses may reduce falls. However, the ability of people with PD to improve postural responses with practice is poorly understood. Our objective was to determine whether people with PD can improve protective postural responses similarly to healthy adults through repeated perturbations, and whether improvements are retained or generalize to untrained perturbations. Twelve healthy adults and 15 people with PD underwent 25 forward and 25 backward translations of the support surface, eliciting backward, and forward protective steps, respectively. We assessed whether: (1) performance improved over one day of practice, (2) changes were retained 24 h later, and (3) improvements generalized to untrained (lateral) postural responses. People with PD and healthy adults improved postural response characteristics, including center of mass displacement after p...
Archives of physical medicine and rehabilitation, Jan 18, 2015
Characterize postural responses to forward and backward external perturbations in people with mul... more Characterize postural responses to forward and backward external perturbations in people with multiple sclerosis (PwMS), and relate performance to commonly-used clinical outcomes. Cross-sectional study. Postural responses were tested during large "stepping" and smaller "feet-in-place" perturbations in forward and backward directions. University research laboratory PARTICIPANTS: 54 PwMS and 21 age-matched controls INTERVENTION: Not applicable MAIN OUTCOME MEASURES: Center of mass displacement, step latency RESULTS: PwMS exhibited larger center of mass displacement and step latency than control participants in response to "stepping" perturbations (p=0.003 and p=0.028, respectively). Stepping deficits were more pronounced during backward stepping and were significantly correlated to increased severity on clinical measures (European Database for Multiple Sclerosis Disability Score and Timed 25-Foot Walk). Compensatory stepping is impaired in PwMS, and corre...
Journal of neurology, neurosurgery, and psychiatry, Jan 15, 2014
Freezing of gait in people with Parkinson's disease (PD) is likely related to attentional con... more Freezing of gait in people with Parkinson's disease (PD) is likely related to attentional control (ie, ability to divide and switch attention). However, the neural pathophysiology of altered attentional control in individuals with PD who freeze is unknown. Structural connectivity of the pedunculopontine nucleus has been related to freezing and may play a role in altered attentional control; however, this relationship has not been investigated. We measured whether dual-task interference, defined as the reduction in gait performance during dual-task walking, is more pronounced in individuals with PD who freeze, and whether dual-task interference is associated with structural connectivity and/or executive function in this population. We measured stride length in 13 people with PD with and 12 without freezing of gait during normal and dual-task walking. We also assessed asymmetry of pedunculopontine nucleus structural connectivity via diffusion tensor imaging and performance on cogn...
Motor imagery during functional magnetic resonance imaging is commonly used to understand the neu... more Motor imagery during functional magnetic resonance imaging is commonly used to understand the neural underpinnings of complex movements. This approach has recently been applied to individuals with Parkinson disease (PD) to better understand how brain function may relate to movement dysfunction. However, the ability of individuals with PD to imagine movements when "Off" dopamine replacement medication is poorly understood. Therefore, the primary purpose of the current study is to test the ability of people with PD to imagine movements while "On" and "Off" anti-Parkinson medication. Vividness of imagery was assessed in 28 individuals with mild to moderate PD (Hoehn and Yahr stages 1-3) via the Kinesthetic Visual Imagery Questionnaire (KVIQ-20) both "On" and "Off" anti-Parkinson medication. Vividness of imagery of 32 age-matched older adults was also assessed. No differences in vividness of imagery were observed between "Off" ...
We developed a questionnaire to assess motor imagery (MI) of gait and administered it to 33 contr... more We developed a questionnaire to assess motor imagery (MI) of gait and administered it to 33 controls and 28 individuals with PD. Our goals were: 1) compare gait MI in individuals with and without PD, 2) determine whether walking performance relates to gait MI and 3) compare gait MI in individuals with PD with and without freezing of gait. Gait MI was not different between PD and controls. There was no correlation between walking performance and gait MI, and no difference in gait MI between freezers and nonfreezers. The gait imagery questionnaire may be useful for imaging studies involving imagined gait.
Motor imagery during functional magnetic resonance imaging (fMRI) allows assessment of brain acti... more Motor imagery during functional magnetic resonance imaging (fMRI) allows assessment of brain activity during tasks, like walking, that cannot be completed in an MRI scanner. We used gait imagery to assess the neural pathophysiology of locomotion in Parkinson disease (PD). Brain activity was measured in five locomotor regions (supplementary motor area (SMA), globus pallidus (GP), putamen, mesencephalic locomotor region, cerebellar locomotor region) during simple (forward) and complex (backward, turning) gait imagery. Brain activity was correlated to overground walking velocity. Across tasks, PD exhibited reduced activity in the globus pallidus compared to controls. People with PD, but not controls, exhibited more activity in the SMA during imagined turning compared to forward or backward walking. In PD, walking speed was correlated to brain activity in several regions. Altered SMA activity in PD during imagined turning may represent compensatory neural adaptations during complex gait. The lowered activity and positive correlation to locomotor function in GP suggests reduced activity in this region may relate to locomotor dysfunction. This study elucidates changes in neural activity during gait in PD, underscoring the importance of testing simple and complex tasks. Results support a positive relationship between activity in locomotor regions and walking ability.
People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive d... more People with Parkinson disease (PD) who show freezing of gait also have dysfunction in cognitive domains that interact with mobility. Specifically, freezing of gait is associated with executive dysfunction involving response inhibition, divided attention or switching attention, and visuospatial function. The neural control impairments leading to freezing of gait have recently been attributed to higher-level, executive and attentional cortical processes involved in coordinating posture and gait rather than to lower-level, sensorimotor impairments. To date, rehabilitation for freezing of gait primarily has focused on compensatory mobility training to overcome freezing events, such as sensory cueing and voluntary step planning. Recently, a few interventions have focused on restitutive, rather than compensatory, therapy. Given the documented impairments in executive function specific to patients with PD who freeze and increasing evidence of overlap between cognitive and motor function, incorporating cognitive challenges with mobility training may have important benefits for patients with freezing of gait. Thus, a novel theoretical framework is proposed for exercise interventions that jointly address both the specific cognitive and mobility challenges of people with PD who freeze.
Protective postural responses to external perturbations are hypokinetic in people with Parkinson&... more Protective postural responses to external perturbations are hypokinetic in people with Parkinson's disease (PD), and improving these responses may reduce falls. However, the ability of people with PD to improve postural responses with practice is poorly understood. Our objective was to determine whether people with PD can improve protective postural responses similarly to healthy adults through repeated perturbations, and whether improvements are retained or generalize to untrained perturbations. Twelve healthy adults and 15 people with PD underwent 25 forward and 25 backward translations of the support surface, eliciting backward, and forward protective steps, respectively. We assessed whether: (1) performance improved over one day of practice, (2) changes were retained 24 h later, and (3) improvements generalized to untrained (lateral) postural responses. People with PD and healthy adults improved postural response characteristics, including center of mass displacement after p...
Archives of physical medicine and rehabilitation, Jan 18, 2015
Characterize postural responses to forward and backward external perturbations in people with mul... more Characterize postural responses to forward and backward external perturbations in people with multiple sclerosis (PwMS), and relate performance to commonly-used clinical outcomes. Cross-sectional study. Postural responses were tested during large "stepping" and smaller "feet-in-place" perturbations in forward and backward directions. University research laboratory PARTICIPANTS: 54 PwMS and 21 age-matched controls INTERVENTION: Not applicable MAIN OUTCOME MEASURES: Center of mass displacement, step latency RESULTS: PwMS exhibited larger center of mass displacement and step latency than control participants in response to "stepping" perturbations (p=0.003 and p=0.028, respectively). Stepping deficits were more pronounced during backward stepping and were significantly correlated to increased severity on clinical measures (European Database for Multiple Sclerosis Disability Score and Timed 25-Foot Walk). Compensatory stepping is impaired in PwMS, and corre...
Journal of neurology, neurosurgery, and psychiatry, Jan 15, 2014
Freezing of gait in people with Parkinson's disease (PD) is likely related to attentional con... more Freezing of gait in people with Parkinson's disease (PD) is likely related to attentional control (ie, ability to divide and switch attention). However, the neural pathophysiology of altered attentional control in individuals with PD who freeze is unknown. Structural connectivity of the pedunculopontine nucleus has been related to freezing and may play a role in altered attentional control; however, this relationship has not been investigated. We measured whether dual-task interference, defined as the reduction in gait performance during dual-task walking, is more pronounced in individuals with PD who freeze, and whether dual-task interference is associated with structural connectivity and/or executive function in this population. We measured stride length in 13 people with PD with and 12 without freezing of gait during normal and dual-task walking. We also assessed asymmetry of pedunculopontine nucleus structural connectivity via diffusion tensor imaging and performance on cogn...
Motor imagery during functional magnetic resonance imaging is commonly used to understand the neu... more Motor imagery during functional magnetic resonance imaging is commonly used to understand the neural underpinnings of complex movements. This approach has recently been applied to individuals with Parkinson disease (PD) to better understand how brain function may relate to movement dysfunction. However, the ability of individuals with PD to imagine movements when "Off" dopamine replacement medication is poorly understood. Therefore, the primary purpose of the current study is to test the ability of people with PD to imagine movements while "On" and "Off" anti-Parkinson medication. Vividness of imagery was assessed in 28 individuals with mild to moderate PD (Hoehn and Yahr stages 1-3) via the Kinesthetic Visual Imagery Questionnaire (KVIQ-20) both "On" and "Off" anti-Parkinson medication. Vividness of imagery of 32 age-matched older adults was also assessed. No differences in vividness of imagery were observed between "Off" ...
We developed a questionnaire to assess motor imagery (MI) of gait and administered it to 33 contr... more We developed a questionnaire to assess motor imagery (MI) of gait and administered it to 33 controls and 28 individuals with PD. Our goals were: 1) compare gait MI in individuals with and without PD, 2) determine whether walking performance relates to gait MI and 3) compare gait MI in individuals with PD with and without freezing of gait. Gait MI was not different between PD and controls. There was no correlation between walking performance and gait MI, and no difference in gait MI between freezers and nonfreezers. The gait imagery questionnaire may be useful for imaging studies involving imagined gait.
Motor imagery during functional magnetic resonance imaging (fMRI) allows assessment of brain acti... more Motor imagery during functional magnetic resonance imaging (fMRI) allows assessment of brain activity during tasks, like walking, that cannot be completed in an MRI scanner. We used gait imagery to assess the neural pathophysiology of locomotion in Parkinson disease (PD). Brain activity was measured in five locomotor regions (supplementary motor area (SMA), globus pallidus (GP), putamen, mesencephalic locomotor region, cerebellar locomotor region) during simple (forward) and complex (backward, turning) gait imagery. Brain activity was correlated to overground walking velocity. Across tasks, PD exhibited reduced activity in the globus pallidus compared to controls. People with PD, but not controls, exhibited more activity in the SMA during imagined turning compared to forward or backward walking. In PD, walking speed was correlated to brain activity in several regions. Altered SMA activity in PD during imagined turning may represent compensatory neural adaptations during complex gait. The lowered activity and positive correlation to locomotor function in GP suggests reduced activity in this region may relate to locomotor dysfunction. This study elucidates changes in neural activity during gait in PD, underscoring the importance of testing simple and complex tasks. Results support a positive relationship between activity in locomotor regions and walking ability.
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