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Commentary: An evaluation of mechanisms underlying the influence of step cues on gait in Parkinson’s disease
Journal of Clinical Neuroscience 18 (2011) 803
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Commentary
Commentary: An evaluation of mechanisms underlying the influence of step cues on gait in Parkinson’s disease q Simon J.G. Lewis ⇑ Parkinson’s Disease Research Clinic, Brain & Mind Research Institute, Level 4, Building F, 94 Mallett Street, Camperdown, New South Wales 2050, Australia
a r t i c l e
i n f o
Article history: Received 7 August 2010 Accepted 20 December 2010
Keywords: Cueing Freezing Gait Parkinson’s disease Proprioceptive processing
a b s t r a c t As patients lose their physical independence, disturbances in gait are a leading cause for institutional care in Parkinson’s disease (PD). For many years, clinicians have acknowledged the role that external visual cues often have on improving gait in PD. In this issue of the Journal of Clinical Neuroscience, C.A. Lebold and Q.J. Almeida present data that dissects out the roles of focused attention and proprioceptive processing in the amelioration of gait deficits. Their findings suggest that focused visual attention on the lower limbs in PD may be compensating for a deficit in proprioceptive processing. This study highlights the potential therapeutic benefits of strategies that could tap into this mechanism. Ó 2011 Elsevier Ltd. All rights reserved.
1. Commentary Parkinson’s disease (PD) affects 1% to 2% of the population aged over 60 years of age and results in significant health and socioeconomic burdens. Despite major treatment advances and a greater understanding of the condition since James Parkinson’s original description in 1817, PD is still associated with high rates of institutional care. Much of this loss in independence relates to the progressive deterioration of gait seen in the advanced stages. For many years, clinicians have acknowledged the role that external visual cues often have on improving gait in PD. It has been postulated that the striatal dopamine depletion occurring in PD impairs ‘‘internal drivers’’ that regulate the automaticity of gait, leading patients to become more reliant on ‘‘external drivers’’ operating at a cortical level. Thus cueing through various sensory stimuli, such as lines on the ground, might act to focus attention and allow the more planned execution of movement. Over half of patients in the advanced stages of PD can suffer paroxysmal freezing episodes where there is a complete disruption of gait. Interestingly, previous work has demonstrated that forced reductions in stride length among these patients can trigger freezing episodes.1 Thus it is of great clinical relevance to understand the factors that can improve step length in PD and their underlying neural correlates. In this issue of the Journal of Clinical Neuroscience, C.A. Lebold and Q.J. Almeida2 present data that dissects out the roles of focused attention and proprioceptive processing in the amelioration of gait q Disclosure of Funding: Rolf Edgar Lake Scholarship, Michael J. Fox Foundation, NHMRC. ⇑ Tel.: +61 2 9351 0702; fax: +61 2 9351 0855. E-mail address: [email protected]
0967-5868/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2010.12.006
deficits. The appreciation of movement when an individual is moving through the external environment is known as optic flow, with initial processing occurring at the retina before cortical integration. Thus, the improvements in step length observed in patients using lines on the floor to assist gait may tap into enhancing optic flow. However, in this study the investigators reported similar improvements in step length when patients were presented with parallel lines on the floor acting as visual cues, as well as in a condition of ‘‘reverse optic flow’’ where a laser device projected a line that constantly moved away from patients as they walked forwards. Furthermore, step length was not improved when the ‘‘reverse optic flow’’ condition was performed in the dark, where patients could not see their legs or the external environment while trying to utilise the visual cue. These findings suggest that visual cueing to enhance more conscious, goal directed behaviour that bypasses impaired basal ganglia function may not be sufficient to explain improvements in step length. Indeed, the results presented suggest that visual cueing may focus attention toward the lower limbs, acting to compensate for a deficit in proprioceptive processing. This study highlights the potential therapeutic benefits of strategies that could tap into this mechanism.
References 1. Chee R, Murphy A, Danoudis M, et al. Gait freezing in Parkinson’s disease and the stride length sequence effect interaction. Brain 2009;132:2151–60. 2. Lebold CA, Almeida QJ. An evaluation of mechanisms underlying the influence of step cues on gait in parkinson’s disease. J Clin Neurosci 2011;18:798–802.
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Commentary
Commentary: An evaluation of mechanisms underlying the influence of step cues on gait in Parkinson’s disease q Simon J.G. Lewis ⇑ Parkinson’s Disease Research Clinic, Brain & Mind Research Institute, Level 4, Building F, 94 Mallett Street, Camperdown, New South Wales 2050, Australia
a r t i c l e
i n f o
Article history: Received 7 August 2010 Accepted 20 December 2010
Keywords: Cueing Freezing Gait Parkinson’s disease Proprioceptive processing
a b s t r a c t As patients lose their physical independence, disturbances in gait are a leading cause for institutional care in Parkinson’s disease (PD). For many years, clinicians have acknowledged the role that external visual cues often have on improving gait in PD. In this issue of the Journal of Clinical Neuroscience, C.A. Lebold and Q.J. Almeida present data that dissects out the roles of focused attention and proprioceptive processing in the amelioration of gait deficits. Their findings suggest that focused visual attention on the lower limbs in PD may be compensating for a deficit in proprioceptive processing. This study highlights the potential therapeutic benefits of strategies that could tap into this mechanism. Ó 2011 Elsevier Ltd. All rights reserved.
1. Commentary Parkinson’s disease (PD) affects 1% to 2% of the population aged over 60 years of age and results in significant health and socioeconomic burdens. Despite major treatment advances and a greater understanding of the condition since James Parkinson’s original description in 1817, PD is still associated with high rates of institutional care. Much of this loss in independence relates to the progressive deterioration of gait seen in the advanced stages. For many years, clinicians have acknowledged the role that external visual cues often have on improving gait in PD. It has been postulated that the striatal dopamine depletion occurring in PD impairs ‘‘internal drivers’’ that regulate the automaticity of gait, leading patients to become more reliant on ‘‘external drivers’’ operating at a cortical level. Thus cueing through various sensory stimuli, such as lines on the ground, might act to focus attention and allow the more planned execution of movement. Over half of patients in the advanced stages of PD can suffer paroxysmal freezing episodes where there is a complete disruption of gait. Interestingly, previous work has demonstrated that forced reductions in stride length among these patients can trigger freezing episodes.1 Thus it is of great clinical relevance to understand the factors that can improve step length in PD and their underlying neural correlates. In this issue of the Journal of Clinical Neuroscience, C.A. Lebold and Q.J. Almeida2 present data that dissects out the roles of focused attention and proprioceptive processing in the amelioration of gait q Disclosure of Funding: Rolf Edgar Lake Scholarship, Michael J. Fox Foundation, NHMRC. ⇑ Tel.: +61 2 9351 0702; fax: +61 2 9351 0855. E-mail address: [email protected]
0967-5868/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2010.12.006
deficits. The appreciation of movement when an individual is moving through the external environment is known as optic flow, with initial processing occurring at the retina before cortical integration. Thus, the improvements in step length observed in patients using lines on the floor to assist gait may tap into enhancing optic flow. However, in this study the investigators reported similar improvements in step length when patients were presented with parallel lines on the floor acting as visual cues, as well as in a condition of ‘‘reverse optic flow’’ where a laser device projected a line that constantly moved away from patients as they walked forwards. Furthermore, step length was not improved when the ‘‘reverse optic flow’’ condition was performed in the dark, where patients could not see their legs or the external environment while trying to utilise the visual cue. These findings suggest that visual cueing to enhance more conscious, goal directed behaviour that bypasses impaired basal ganglia function may not be sufficient to explain improvements in step length. Indeed, the results presented suggest that visual cueing may focus attention toward the lower limbs, acting to compensate for a deficit in proprioceptive processing. This study highlights the potential therapeutic benefits of strategies that could tap into this mechanism.
References 1. Chee R, Murphy A, Danoudis M, et al. Gait freezing in Parkinson’s disease and the stride length sequence effect interaction. Brain 2009;132:2151–60. 2. Lebold CA, Almeida QJ. An evaluation of mechanisms underlying the influence of step cues on gait in parkinson’s disease. J Clin Neurosci 2011;18:798–802.