The remarkable increase in human life expectancy over the past century has been achieved at the e... more The remarkable increase in human life expectancy over the past century has been achieved at the expense of the risk of age-related impairment and disease. Neurodegeneration, be it part of normal aging or due to neurodegenerative disorders, is characterized by loss of specific neuronal populations, leading to increasing clinical impairment. The individual course may be described as balance between aging-or disease-related pathology and intrinsic mechanisms of adaptation. There is plenty of evidence that the human brain is provided with exhaustible resources to maintain function in the face of adverse conditions. While a reserve concept has mainly been coined in cognitive neuroscience, emerging evidence suggests similar mechanisms to underlie individual differences of adaptive capacity within the motor system. In this narrative review, we summarize what has been proposed to date about a motor reserve (mR) framework. We present current evidence from research in aging subjects and people with neurological conditions, followed by a description of what is known about potential neuronal substrates of mR so far. As there is no gold standard of mR quantification, we outline current approaches which describe various indicators of mR. We conclude by sketching out potential future directions of research. Expediting our understanding of differences in individual motor resilience towards aging and disease will eventually contribute to new, individually tailored therapeutic strategies. Provided early diagnosis, enhancing the individual mR may be suited to postpone disease onset by years and may be an efficacious contribution towards healthy aging, with an increased quality of life for the elderly.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by demye... more Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by demyelination and neurodegeneration, leading to focal lesions in both the white and the grey matter [1]. The underlying causes and mechanisms behind this chronic disease remain opaque. People with MS (PwMS) are faced with a wide range of symptoms, including disturbances of gait, coordination and vision, as well as pain, fatigue, depression and tremor [2]. Initially, the majority of PwMS present with a relapsing-remitting disease course, but
Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning usi... more Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning using transcranial direct current stimulation (tDCS). An important point of discussion regarding this modulation is the optimal timing of tDCS, as this parameter could significantly influence the outcome. Hence, this study aimed to investigate the effects of the timing of cerebellar anodal tDCS (ca-tDCS) on motor learning using a sequential finger-tapping task (FTT). Methods: One hundred and twenty two healthy young, right-handed subjects (96 females) were randomized into four groups (During sham , Before, During real , After). They performed 2 days of FTT with their non-dominant hand on a custom keyboard. The task consisted of 40 s of typing followed by 20 s rest. Each participant received ca-tDCS (2 mA, sponge electrodes of 25 cm 2 , 20 min) at the appropriate timing and performed 20 trials on the first day (T1, 20 min). On the following day, only 10 trials of FTT were performed without tDCS (T2, 10 min). Motor skill performance and retention were assessed. Results: All participants showed a time-dependent increase in learning. Motor performance was not different between groups at the end of T1 (p = 0.59). ca-tDCS did not facilitate the retention of the motor skill in the FTT at T2 (p = 0.27). Thus, our findings indicate an absence of the effect of ca-tDCS on motor performance or retention of the FTT independently from the timing of stimulation. Conclusion: The present results suggest that the outcome of ca-tDCS is highly dependent on the task and stimulation parameters. Future studies need to establish a clear basis for the successful and reproducible clinical application of ca-tDCS.
Mental rotation (mR) bases on imagination of actual movements. It remains unclear whether there i... more Mental rotation (mR) bases on imagination of actual movements. It remains unclear whether there is a specific pattern of mR impairment in focal dystonia. We aimed to investigate mR in patients with cervical dystonia (CD) and blepharospasm (BS) and to assess potential confounders. 23 CD patients and 23 healthy controls (HC) as well as 21 BS and 19 hemifacial spasm (HS) patients were matched for sex, age, and education level. Handedness, finger dexterity, general reaction time, and cognitive status were assessed. Disease severity was evaluated by clinical scales. During mR, photographs of body parts (head, hand, or foot) and a non-corporal object (car) were displayed at different angles rotated within their plane. Subjects were asked to judge laterality of the presented image by keystroke. Both speed and correctness were evaluated. Compared to HC, CD and HS patients performed worse in mR of hands, whereas BS group showed comparable performance. There was a significant association of prolonged mR reaction time (RT) with reduced MoCA scores and with increased RT in an unspecific reaction speed task. After exclusion of cognitively impaired patients, increased RT in the mR of hands was confined to CD group, but not HS. While the question of whether specific patterns of mR impairment reliably define a dystonic endophenotype remains elusive, our findings point to mR as a useful tool, when used carefully with control measures and tasks, which may be capable of identifying specific deficits that distinguish between subtypes of dystonia. Abbreviations ANOVA Analyses of variances BS Blepharospasm CD Cervical dystonia HC Healthy controls HS Hemifacial spasm MoCA Montreal Cognitive Assessment mR Mental rotation ORRT Online Reaction Time Test RT Reaction time(s) SD Standard deviation sec. Seconds TWSTRS Toronto Western Spasmodic Torticollis Rating Scale WC Writer's cramp 9HPT 9-Hole-Peg-Test Dystonia is a hyperkinetic movement disorder syndrome which is still considered a rare disease 1. The key feature of dystonia is involuntary muscle contraction causing abnormal and partly bizarre postures of different body parts. According to body distribution, focal, segmental, multifocal, and generalized forms of dystonia have been defined 2. Non-motor symptoms like depression, pain and sleep disorders are quite common and, in addition to the motor symptoms, may severely affect patients' quality of life 3. Despite being first described by Oppenheim as early as 1911, over a hundred years ago, the pathophysiology of dystonia remains poorly understood. Three potential pathophysiological mechanisms are frequently discussed
Background: Aging increases individual susceptibility to falls and injuries, suggesting poorer ad... more Background: Aging increases individual susceptibility to falls and injuries, suggesting poorer adaptation of balance responses to perturbation during locomotion, which can be measured with the locomotor adaptation task (LAT). However, it is unclear how aging and lifestyle factors affect these responses during walking. Hence, the present study investigates the relationship between balance and lifestyle factors during the LAT in healthy individuals across the adult lifespan using a correlational design. Methods: Thirty participants aged 20–78 years performed an LAT on a split-belt treadmill (SBT). We evaluated the magnitude and rate of adaptation and deadaptation during the LAT. Participants reported their lifelong physical and cognitive activity. Results: Age positively correlated with gait-line length asymmetry at the late post-adaptation phase (p = 0.007). These age-related effects were mediated by recent physical activity levels (p = 0.040). Conclusion: Our results confirm that lo...
Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning usi... more Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning using transcranial direct current stimulation (tDCS). An important point of discussion regarding this modulation is the optimal timing of tDCS, as this parameter could significantly influence the outcome. Hence, this study aimed to investigate the effects of the timing of cerebellar anodal tDCS (ca-tDCS) on motor learning using a sequential finger-tapping task (FTT). Methods: One hundred and twenty two healthy young, right-handed subjects (96 females) were randomized into four groups (Duringsham, Before, Duringreal, After). They performed 2 days of FTT with their non-dominant hand on a custom keyboard. The task consisted of 40 s of typing followed by 20 s rest. Each participant received ca-tDCS (2 mA, sponge electrodes of 25 cm2, 20 min) at the appropriate timing and performed 20 trials on the first day (T1, 20 min). On the following day, only 10 trials of FTT were performed without tDCS (T...
The remarkable increase in human life expectancy over the past century has been achieved at the e... more The remarkable increase in human life expectancy over the past century has been achieved at the expense of the risk of age-related impairment and disease. Neurodegeneration, be it part of normal aging or due to neurodegenerative disorders, is characterized by loss of specific neuronal populations, leading to increasing clinical impairment. The individual course may be described as balance between aging-or disease-related pathology and intrinsic mechanisms of adaptation. There is plenty of evidence that the human brain is provided with exhaustible resources to maintain function in the face of adverse conditions. While a reserve concept has mainly been coined in cognitive neuroscience, emerging evidence suggests similar mechanisms to underlie individual differences of adaptive capacity within the motor system. In this narrative review, we summarize what has been proposed to date about a motor reserve (mR) framework. We present current evidence from research in aging subjects and people with neurological conditions, followed by a description of what is known about potential neuronal substrates of mR so far. As there is no gold standard of mR quantification, we outline current approaches which describe various indicators of mR. We conclude by sketching out potential future directions of research. Expediting our understanding of differences in individual motor resilience towards aging and disease will eventually contribute to new, individually tailored therapeutic strategies. Provided early diagnosis, enhancing the individual mR may be suited to postpone disease onset by years and may be an efficacious contribution towards healthy aging, with an increased quality of life for the elderly.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by demye... more Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by demyelination and neurodegeneration, leading to focal lesions in both the white and the grey matter [1]. The underlying causes and mechanisms behind this chronic disease remain opaque. People with MS (PwMS) are faced with a wide range of symptoms, including disturbances of gait, coordination and vision, as well as pain, fatigue, depression and tremor [2]. Initially, the majority of PwMS present with a relapsing-remitting disease course, but
Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning usi... more Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning using transcranial direct current stimulation (tDCS). An important point of discussion regarding this modulation is the optimal timing of tDCS, as this parameter could significantly influence the outcome. Hence, this study aimed to investigate the effects of the timing of cerebellar anodal tDCS (ca-tDCS) on motor learning using a sequential finger-tapping task (FTT). Methods: One hundred and twenty two healthy young, right-handed subjects (96 females) were randomized into four groups (During sham , Before, During real , After). They performed 2 days of FTT with their non-dominant hand on a custom keyboard. The task consisted of 40 s of typing followed by 20 s rest. Each participant received ca-tDCS (2 mA, sponge electrodes of 25 cm 2 , 20 min) at the appropriate timing and performed 20 trials on the first day (T1, 20 min). On the following day, only 10 trials of FTT were performed without tDCS (T2, 10 min). Motor skill performance and retention were assessed. Results: All participants showed a time-dependent increase in learning. Motor performance was not different between groups at the end of T1 (p = 0.59). ca-tDCS did not facilitate the retention of the motor skill in the FTT at T2 (p = 0.27). Thus, our findings indicate an absence of the effect of ca-tDCS on motor performance or retention of the FTT independently from the timing of stimulation. Conclusion: The present results suggest that the outcome of ca-tDCS is highly dependent on the task and stimulation parameters. Future studies need to establish a clear basis for the successful and reproducible clinical application of ca-tDCS.
Mental rotation (mR) bases on imagination of actual movements. It remains unclear whether there i... more Mental rotation (mR) bases on imagination of actual movements. It remains unclear whether there is a specific pattern of mR impairment in focal dystonia. We aimed to investigate mR in patients with cervical dystonia (CD) and blepharospasm (BS) and to assess potential confounders. 23 CD patients and 23 healthy controls (HC) as well as 21 BS and 19 hemifacial spasm (HS) patients were matched for sex, age, and education level. Handedness, finger dexterity, general reaction time, and cognitive status were assessed. Disease severity was evaluated by clinical scales. During mR, photographs of body parts (head, hand, or foot) and a non-corporal object (car) were displayed at different angles rotated within their plane. Subjects were asked to judge laterality of the presented image by keystroke. Both speed and correctness were evaluated. Compared to HC, CD and HS patients performed worse in mR of hands, whereas BS group showed comparable performance. There was a significant association of prolonged mR reaction time (RT) with reduced MoCA scores and with increased RT in an unspecific reaction speed task. After exclusion of cognitively impaired patients, increased RT in the mR of hands was confined to CD group, but not HS. While the question of whether specific patterns of mR impairment reliably define a dystonic endophenotype remains elusive, our findings point to mR as a useful tool, when used carefully with control measures and tasks, which may be capable of identifying specific deficits that distinguish between subtypes of dystonia. Abbreviations ANOVA Analyses of variances BS Blepharospasm CD Cervical dystonia HC Healthy controls HS Hemifacial spasm MoCA Montreal Cognitive Assessment mR Mental rotation ORRT Online Reaction Time Test RT Reaction time(s) SD Standard deviation sec. Seconds TWSTRS Toronto Western Spasmodic Torticollis Rating Scale WC Writer's cramp 9HPT 9-Hole-Peg-Test Dystonia is a hyperkinetic movement disorder syndrome which is still considered a rare disease 1. The key feature of dystonia is involuntary muscle contraction causing abnormal and partly bizarre postures of different body parts. According to body distribution, focal, segmental, multifocal, and generalized forms of dystonia have been defined 2. Non-motor symptoms like depression, pain and sleep disorders are quite common and, in addition to the motor symptoms, may severely affect patients' quality of life 3. Despite being first described by Oppenheim as early as 1911, over a hundred years ago, the pathophysiology of dystonia remains poorly understood. Three potential pathophysiological mechanisms are frequently discussed
Background: Aging increases individual susceptibility to falls and injuries, suggesting poorer ad... more Background: Aging increases individual susceptibility to falls and injuries, suggesting poorer adaptation of balance responses to perturbation during locomotion, which can be measured with the locomotor adaptation task (LAT). However, it is unclear how aging and lifestyle factors affect these responses during walking. Hence, the present study investigates the relationship between balance and lifestyle factors during the LAT in healthy individuals across the adult lifespan using a correlational design. Methods: Thirty participants aged 20–78 years performed an LAT on a split-belt treadmill (SBT). We evaluated the magnitude and rate of adaptation and deadaptation during the LAT. Participants reported their lifelong physical and cognitive activity. Results: Age positively correlated with gait-line length asymmetry at the late post-adaptation phase (p = 0.007). These age-related effects were mediated by recent physical activity levels (p = 0.040). Conclusion: Our results confirm that lo...
Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning usi... more Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning using transcranial direct current stimulation (tDCS). An important point of discussion regarding this modulation is the optimal timing of tDCS, as this parameter could significantly influence the outcome. Hence, this study aimed to investigate the effects of the timing of cerebellar anodal tDCS (ca-tDCS) on motor learning using a sequential finger-tapping task (FTT). Methods: One hundred and twenty two healthy young, right-handed subjects (96 females) were randomized into four groups (Duringsham, Before, Duringreal, After). They performed 2 days of FTT with their non-dominant hand on a custom keyboard. The task consisted of 40 s of typing followed by 20 s rest. Each participant received ca-tDCS (2 mA, sponge electrodes of 25 cm2, 20 min) at the appropriate timing and performed 20 trials on the first day (T1, 20 min). On the following day, only 10 trials of FTT were performed without tDCS (T...
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