Ranganathan R.,Rehabilitation Institute of Chicago
Journal of neurophysiology | Year: 2012
There has been extensive debate as to whether muscle synergies in motor tasks reflect underlying neural organization or simply correlations in muscle activity that are imposed by the task. One possible means of distinguishing these two alternatives is through the analysis of variability in the electromyogram (EMG). Here, we simulated EMG in eight lower-limb muscles and introduced hypothetical neural coupling between specific muscle groups. Neural coupling was simulated by introducing correlations in the neural activation commands to different muscles (positive, negative, or zero coupling). When the entire EMG signal was used for analysis, the extracted synergies reflected only simultaneous muscle activity, regardless of the neural coupling between the muscles. On the other hand, examining the variability in the EMG after subtracting the ensemble average was successful in identifying the simulated neural coupling. The extracted synergies from these two methods were also different when we analyzed data from participants during treadmill walking. The results emphasize the importance of examining EMG variability to understand the neural basis of muscle synergies.
Cammarata M.L.,Rehabilitation Institute of Chicago
Arthritis care & research | Year: 2012
It has been proposed that proprioceptive impairments observed in knee osteoarthritis (OA) may be associated with disease-related changes in joint mechanics. The aim of this study was to quantify joint proprioception and stiffness in the frontal plane of the knee in persons with and without knee OA and to report the associations between these 2 metrics. Participants were 13 patients with knee OA and 14 healthy age-matched subjects. Proprioceptive acuity was assessed in varus and valgus using the threshold to detection of passive movement (TDPM) test. Passive joint stiffness was estimated as the slope of the normalized torque-angle relationship at 0° joint rotation (neutral) and several rotations in varus and valgus. Analyses of variance were performed to determine the effect of OA and sex on each metric. Linear regression was used to assess the correlation between the TDPM and joint stiffness. The TDPM was significantly higher (P < 0.05) in the OA group compared to the control group for both varus and valgus, but significant sex differences were observed. Passive joint stiffness was significantly reduced (P < 0.05) in OA participants compared to the control group in neutral and valgus, but not varus, and significantly reduced in women compared to men. A weak negative correlation was observed between the TDPM and stiffness estimates, suggesting that poorer proprioception was associated with less joint stiffness. While both joint stiffness and proprioception were reduced in the OA population, they were only weakly correlated. This suggests that other neurophysiologic factors play a larger role in the proprioceptive deficits in knee OA. Copyright © 2012 by the American College of Rheumatology.
Harden R.N.,Rehabilitation Institute of Chicago
Postgraduate medicine | Year: 2013
This article aims to help primary care physicians negotiate gaps in current guidelines for postherpetic neuralgia (PHN). The objectives of this article are to: 1) briefly review the available guidelines and identify their strengths and weaknesses; 2) review the gaps in the guidelines; 3) review new data that were not included in the most recent guidelines; 4) provide expert opinion on how the new data and current guidelines can be used to make treatment decisions; and 5) review several important dimensions of care (eg, tolerability, dosing) and provide guidance. In general, all guidelines recognize the α2δ ligands, tricyclic antidepressants (TCAs), opioids, and tramadol as efficacious systemic options, with topical lidocaine serving as an efficacious nonsystemic approach for localized PHN treatment. The first-line treatment options typically recommended in the guidelines are α2δ ligands and TCAs, while opioids and tramadol are often recommended as second- or third-line options. Since the latest guidelines were published, newer agents (eg, topical capsaicin [8%] patch and gastroretentive gabapentin) have met the standard as first-line therapy with the publication of ≥ 1 randomized controlled trial. However, gabapentin enacarbil has not met this standard due to a lack of a published randomized controlled trial in PHN.
Zhou P.,Rehabilitation Institute of Chicago
Journal of neuroengineering and rehabilitation | Year: 2012
High-density surface electromyography (HD-SEMG) has recently emerged as a potentially useful tool in the evaluation of amyotrophic lateral sclerosis (ALS). This study addresses a practical constraint that arises when applying HD-SEMG for supporting the diagnosis of ALS; specifically, how long the surface EMG should be recorded before one can be confident that fasciculation potentials (FPs) are absent in a muscle being tested. HD-SEMG recordings of 29 muscles from 11 ALS patients were analyzed. We used the distribution of intervals between FPs, and estimated the observation duration needed to record from one to five FPs with a probability approaching unity. Such an approach was previously tested by Mills with a concentric needle electrode. We found that the duration of recording was up to 70 s in order to record a single FP with a probability approaching unity. Increasing recording time to 2 minutes, the probability of recording five FPs approached approximately 0.95. HD-SEMG appears to be a suitable method for capturing FPs comparable to intramuscular needle EMG.
Dvorkin A.Y.,Rehabilitation Institute of Chicago
Journal of neuroengineering and rehabilitation | Year: 2013
Although common during the early stages of recovery from severe traumatic brain injury (TBI), attention deficits have been scarcely investigated. Encouraging evidence suggests beneficial effects of attention training in more chronic and higher functioning patients. Interactive technology may provide new opportunities for rehabilitation in inpatients who are earlier in their recovery. We designed a "virtually minimal" approach using robot-rendered haptics in a virtual environment to train severely injured inpatients in the early stages of recovery to sustain attention to a visuo-motor task. 21 inpatients with severe TBI completed repetitive reaching toward targets that were both seen and felt. Patients were tested over two consecutive days, experiencing 3 conditions (no haptic feedback, a break-through force, and haptic nudge) in 12 successive, 4-minute blocks. The interactive visuo-haptic environments were well-tolerated and engaging. Patients typically remained attentive to the task. However, patients exhibited attention loss both before (prolonged initiation) and during (pauses during motion) a movement. Compared to no haptic feedback, patients benefited from haptic nudge cues but not break-through forces. As training progressed, patients increased the number of targets acquired and spontaneously improved from one day to the next. Interactive visuo-haptic environments could be beneficial for attention training for severe TBI patients in the early stages of recovery and warrants further and more prolonged clinical testing.