Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Stroke is a leading cause of disability, and the number of stroke survivors continues to rise. Traditional neurorehabilitation strategies aimed at restoring function to weakened limbs provide only modest benefit. New brain stimulation techniques designed to augment traditional neurorehabilitation hold promise for reducing the burden of stroke-related disability. ⋯ Improved outcomes may be obtained with activity-dependent stimulation, in which brain stimulation is contingent on neural or muscular activity during normal behavior. We review the evidence for improved motor function in stroke patients treated with rTMS, tDCS, and ECS and discuss the mediating physiological mechanisms. We compare these techniques to activity-dependent stimulation, discuss the advantages of this newer strategy for stroke rehabilitation, and suggest future applications for activity-dependent brain stimulation.
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People often fail to detect changes between successively presented tactile patterns, a phenomenon known as tactile change blindness. In this study, we investigated whether changes introduced to tactile patterns are detected better when a participant's attention is focused on the location where the change occurs. Across two experiments, participants (N = 55) were instructed to detect changes between two consecutively presented tactile patterns. ⋯ We found that changes at the attended location were detected more accurately than changes at bodily locations that were unattended. This finding demonstrates that attention can effectively modulate tactile change detection. We discuss the value of this experimental paradigm for investigating excessive attentional focus or hypervigilance to particular regions of the body in various clinical populations.
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Randomized Controlled Trial
Magnified visual feedback exacerbates positional variability in older adults due to altered modulation of the primary agonist muscle.
The purpose of this study was to determine whether magnified visual feedback during position-holding contractions exacerbates the age-associated differences in motor output variability due to changes in the neural activation of the agonist muscle in the upper and lower limb. Twelve young (18-35 years) and ten older adults (65-85 years) were instructed to accurately match a target position at 5° of index finger abduction and ankle dorsiflexion while lifting 10 % of their 1 repetition maximum (1RM) load. Position was maintained at three different visual angles (0.1°, 1°, and 4°) that varied across trials. ⋯ As expected, and independent of limb, older adults exhibited significantly greater positional variability compared with young adults that was exacerbated with magnification of visual feedback (1° and 4°). This increase in variability at the highest magnification of visual feedback was predicted by a decrease in power from 12 to 30 Hz of the agonist EMG signal. These findings demonstrate that motor control in older adults is impaired by magnified visual feedback during positional tasks.
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Comparative Study
Differential working memory correlates for implicit sequence performance in young and older adults.
Our recent work has revealed that visuospatial working memory (VSWM) relates to the rate of explicit motor sequence learning (Bo and Seidler in J Neurophysiol 101:3116-3125, 2009) and implicit sequence performance (Bo et al. in Exp Brain Res 214:73-81, 2011a) in young adults (YA). Although aging has a detrimental impact on many cognitive functions, including working memory, older adults (OA) still rely on their declining working memory resources in an effort to optimize explicit motor sequence learning. Here, we evaluated whether age-related differences in VSWM and/or verbal working memory (VWM) performance relates to implicit performance change in the serial reaction time (SRT) sequence task in OA. ⋯ In YA, the rate of SRT performance change (exponential fit to the performance curve) was significantly correlated with both VSWM and VWM, while in contrast, OA's performance was only correlated with VWM, and not VSWM. These results demonstrate differential reliance on VSWM and VWM for SRT performance between YA and OA. OA may utilize VWM to maintain optimized performance of second-order conditional sequences.
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Previous event-related potential (ERP) and brain imaging studies have suggested observer responses to others' pain are modulated by various bottom-up and top-down factors, including emotional primes. However, the temporal dynamics underlying the impact of emotional primes on responses to others' pain remains poorly understood. In the present study, we explored effects of negative, neutral, and positive emotional priming stimuli on behavioral and cortical responses to visual depictions of others in pain. ⋯ There were no significant differential P3 amplitudes for painful pictures relative to non-painful pictures were found followed neutral and positive emotional primes. These results suggest that negative emotional primes strengthen observers' attention toward others' pain. These results support the threat value of pain hypothesis.