Effect of local and general fatiguing exercises on disturbed and static postural control.

This study compared the effect of local and general fatiguing exercise on disturbed and static postural control performances. Surface electromyography and center of pressure signals were respectively recorded during self-initiated perturbation test and static postural stability test from 7 young male subjects. Local fatiguing exercise was performed using intermittent isometric knee extensions at the level of 40% of maximal voluntary torques. General fatiguing exercise was implemented with rowing ergometer at a speed of 200 ± 5 m/min. Results of disturbed postural tests showed no significant change of anticipatory postural adjustment (APAs) organizations in individual muscles following both fatiguing exercises, but observed larger APAs coactivations in trunk and dorsal muscle pairs following local than general fatiguing exercise, and larger compensatory postural adjustments (CPAs) coactivation in dorsal muscle pair after both fatiguing exercises. In addition, the results of static postural tests indicated efficient static postural stability accompanying the down-weighting of visual input and the up-weighting of vestibular/somatosensory component following both fatiguing exercises. These findings evidenced a general compensation in the central nervous system in response to the neuromuscular deficiencies induced by local fatiguing exercise and put forward the function of sensory recalibration in maintaining postural stability under fatigue conditions.

"Look, Your Muscles Are Firing!": A Qualitative Study of Clinician Perspectives on the Use of Surface Electromyography in Neurorehabilitation.

OBJECTIVE: To examine the perceived value, benefits, drawbacks, and ideas for technology development and implementation of surface electromyography recordings in neurologic rehabilitation practice from clinical stakeholder perspectives. DESIGN: A qualitative, phenomenological study was conducted. In-depth, semistructured interviews and focus groups were completed. Sessions included questions about clinician perspectives and demonstrations of surface electromyography systems to garner perceptions of specific system features. SETTING: The study was conducted at hospital systems in a large metropolitan area. PARTICIPANTS: Adult and pediatric physical therapists, occupational therapists, and physiatrists from inpatient, outpatient, and research settings (N=22) took part in the study. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Interviews and focus groups were audio-recorded, transcribed verbatim, then coded for analysis into themes. RESULTS: Four major themes emerged: (1) low-tech clinical practice and future directions for rehabilitation; (2) barriers to surface electromyography uptake and potential solutions; (3) benefits of surface electromyography for targeted populations; and (4) essential features of surface electromyography systems. CONCLUSIONS: Surface electromyography systems were not routinely utilized for assessment or intervention following neurologic injury. Despite recognition of potential clinical benefits of surface electromyography use, clinicians identified limited time and resources as key barriers to implementation. Perspectives on design and surface electromyography system features indicated the need for streamlined, intuitive, and clinically effective applications. Further research is needed to determine feasibility and clinical relevance of surface electromyography in rehabilitation intervention.

Test-retest reliability of short-interval intracortical inhibition and intracortical facilitation in patients with schizophrenia.

Impaired short-interval intracortical inhibition (SICI) elicited by paired-pulse TMS (ppTMS) has emerged as one of the most consistent TMS findings in patients with schizophrenia. Reduction of SICI has been reproducibly found, suggesting that SICI may be a new biomarker indexing the inhibitory dysfunction in schizophrenia. This study evaluated whether SICI has the test-retest reliability suitable for clinical trial and research applications. SICIs, intracortical facilitation (ICF), and other ppTMS effects were obtained using inter-stimulus intervals (ISIs) from 1 to 500 ms, on 2 occasions about 3-4 weeks apart in patients with schizophrenia and healthy individuals. Acceptable test-retest reliabilities were found for SICI (at 1 and 3 ms ISIs) in both patients and controls (all intraclass correlation coefficients r > 0.6). However, test-retest reliability in longer ISIs and in ICF were modest or poor. To our knowledge, this is the first study demonstrated the acceptable reliability of SICI measure in patients with schizophrenia. The data support SICI as a reliable biomarker for schizophrenia.

Effects of mental workload on physiological and subjective responses during traffic density monitoring: A field study.

This study evaluated operators' mental workload while monitoring traffic density in a city traffic control center. To determine the mental workload, physiological signals (ECG, EMG) were recorded and the NASA-Task Load Index (TLX) was administered for 16 operators. The results showed that the operators experienced a larger mental workload during high traffic density than during low traffic density. The traffic control center stressors caused changes in heart rate variability features and EMG amplitude, although the average workload score was significantly higher in HTD conditions than in LTD conditions. The findings indicated that increasing traffic congestion had a significant effect on HR, RMSSD, SDNN, LF/HF ratio, and EMG amplitude. The results suggested that when operators' workload increases, their mental fatigue and stress level increase and their mental health deteriorate. Therefore, it maybe necessary to implement an ergonomic program to manage mental health. Furthermore, by evaluating mental workload, the traffic control center director can organize the center's traffic congestion operators to sustain the appropriate mental workload and improve traffic control management.

Somatosensory pain is not reliably modulated by weak acoustic stimuli.

BACKGROUND: Pain induced by electrical stimuli has been found in previous research to be reduced by brief, weak electrical pulses, termed prepulses, presented 40 to 60ms prior to the painful electrical stimulus. METHODS: The present experiment investigated the generality of this effect by presenting weak acoustic stimuli simultaneously with, or 80 or 1000ms prior to, painful electric shocks. In the second half of the experimental session, each participant (N=119) was told that the acoustic stimuli would either increase or decrease the pain induced by the electric shock, to investigate automatic and controlled cognitive processes in the modulation of pain. RESULTS: Acoustic stimuli presented simultaneously with painful stimulation increased pain slightly (4mm on a 100mm scale). Acoustic stimuli presented 80 and 1000ms prior to painful stimuli had no effect on pain. Information that acoustic stimuli would increase pain did so in females, but only when the acoustic stimulus was presented 80ms prior to the painful stimulus. CONCLUSIONS: The effect of the acoustic stimuli and of information was weak. Failure to replicate previous findings of decreased pain by weak prepulses was most likely due to the sensory modality of the prepulse stimuli. It is recommended that further studies of pain modulation by brief stimulation use electrical and not acoustic prepulse stimuli.

Spinal Reflexes During Postural Control Under Psychological Pressure.

This study investigated the effect of psychological pressure on spinal reflex excitability. Thirteen participants performed a balancing task by standing on a balance disk with one foot. After six practice trials, they performed one nonpressure and one pressure trial involving a performance-contingent cash reward or punishment. Stress responses were successfully induced; state anxiety, mental effort, and heart rates all increased under pressure. Soleus Hoffmann reflex amplitude in the pressure trial was significantly smaller than in the nonpressure trial. This modification of spinal reflexes may be caused by presynaptic inhibition under the control of higher central nerve excitation under pressure. This change did not prevent 12 of the 13 participants from successfully completing the postural control task under pressure. These results suggest that Hoffmann reflex inhibition would contribute to optimal postural control under stressful situations.

Embodied simulation as part of affective evaluation processes: task dependence of valence concordant EMG activity.

Drawing on recent findings, this study examines whether valence concordant electromyography (EMG) responses can be explained as an unconditional effect of mere stimulus processing or as somatosensory simulation driven by task-dependent processing strategies. While facial EMG over the Corrugator supercilii and the Zygomaticus major was measured, each participant performed two tasks with pictures of album covers. One task was an affective evaluation task and the other was to attribute the album covers to one of five decades. The Embodied Emotion Account predicts that valence concordant EMG is more likely to occur if the task necessitates a somatosensory simulation of the evaluative meaning of stimuli. Results support this prediction with regard to Corrugator supercilii in that valence concordant EMG activity was only present in the affective evaluation task but not in the non-evaluative task. Results for the Zygomaticus major were ambiguous. Our findings are in line with the view that EMG activity is an embodied part of the evaluation process and not a mere physical outcome.

Altering electromyography studies: importance of the electromyographer's perception of patient pain.

OBJECTIVE: To determine the relation between the patient's actual pain, the electromyographer's perception of patient pain, and whether an electromyogram (EMG) is altered. DESIGN: Patients undergoing electromyography reported expected pain and procedure-related overall pain on a 100-mm visual analog scale (VAS). Blinded electromyographers estimated patient pain levels and indicated if they altered the study in any way because of this perception. Multivariable logistic regression was used to determine predictors of altering the EMG. Paired t tests were used to compare overall pain with expected pain and electromyographer perception of pain. SETTING: Tertiary referral center. PARTICIPANTS: Referred sample of adult subjects (N=304). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patient pain, electromyographer perception of patient pain, and whether an EMG was altered because of the electromyographer's perception of patient pain. RESULTS: Mean VAS scores ± SD were 48±25mm for patient-expected pain (P<.001), 42±24mm for electromyographer perception of pain (P<.0001), and 36±25mm for actual overall pain. Electromyographers altered their study 31.7% of the time because of concerns about pain. For every 13-mm increase on the VAS (a prespecified clinically meaningful difference), the electromyographer perception of pain increased the odds of altering a study 2.36 times (95% confidence interval [CI], 1.71-3.26), whereas patient overall pain did not have a significant effect (odds ratio=1.12; 95% CI, .86-1.47). CONCLUSIONS: Patients expect EMGs to be more painful than they are. Electromyographers overestimate patient pain and are more likely to alter their studies when they believe patients are experiencing more pain, independently of whether patients actually have more pain. Improving the communication between electromyographers and patients may prevent unnecessary alterations.

Increases in cAMP, MAPK activity, and CREB phosphorylation during REM sleep: implications for REM sleep and memory consolidation.

The cyclic adenosine monophosphate (cAMP), mitogen-activated protein kinase (MAPK), and cAMP response element-binding protein (CREB) transcriptional pathway is required for consolidation of hippocampus-dependent memory. In mice, this pathway undergoes a circadian oscillation required for memory persistence that reaches a peak during the daytime. Because mice exhibit polyphasic sleep patterns during the day, this suggested the interesting possibility that cAMP, MAPK activity, and CREB phosphorylation may be elevated during sleep. Here, we report that cAMP, phospho-p44/42 MAPK, and phospho-CREB are higher in rapid eye movement (REM) sleep compared with awake mice but are not elevated in non-REM sleep. This peak of activity during REM sleep does not occur in mice lacking calmodulin-stimulated adenylyl cyclases, a mouse strain that learns but cannot consolidate hippocampus-dependent memory. We conclude that a preferential increase in cAMP, MAPK activity, and CREB phosphorylation during REM sleep may contribute to hippocampus-dependent memory consolidation.

Effects of deception for intensity on surface electromyogram (SEMG) activity and blood lactate concentration during intermittent cycling followed by exhaustive cycling.

The purpose of the present study was to determine the effects of deception for exercise intensity on surface electromyogram (SEMG) activity and blood lactate concentration during intermittent cycling exercise (ICE) tests. Sixteen healthy male were randomly assigned to two groups who completed two ICE [three 4-min cycling at 80% peak power output (PPO) with 3-min passive recovery periods followed by exhaustive cycling] tests (ICE-1 and ICE-2). The experimental group (ICED) was deceived of the actual cycling intensity, while the control group (ICEC) was informed of the actual protocol in ICE-2. In ICE-1, both groups were informed of the actual protocol. In ICE-2, root mean square (RMS) calculated from SEMG during submaximal cycling was significantly higher in the ICEC than in the ICED and blood lactate concentration ([La-]) was significantly higher in the ICEC than in the ICED. In particular, the difference in RMS between the groups was also observed during the first 4-min cycling, in which there was no difference in [La-] between the groups. These results suggest that the CNS modulates skeletal muscle recruitment due to the prior deception for exercise intensity.

Abnormal sensorimotor plasticity in CADASIL correlates with neuropsychological impairment.

OBJECTIVE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a small vessel disease of the brain caused by mutations in the NOTCH3 gene. CADASIL progresses, in some cases, to subcortical dementia with a particular cognitive impairment. Different diseases in the dementia spectrum share a central cholinergic and sensorimotor plasticity alteration. We aimed to study different intracortical circuits and sensorimotor plasticity in CADASIL patients using transcranial magnetic stimulation protocols, and to determine whether these characteristics correlated with the results of clinical neuropsychological evaluation. METHODS: Ten CADASIL patients and 10 healthy subjects were included in the study. All subjects underwent a transcranial magnetic stimulation study examining different intracortical circuits. Sensorimotor plasticity was also assessed using a paired associative stimulation and extensive neuropsychological tests. RESULTS: CADASIL patients showed a lack of intracortical facilitation, short latency afferent inhibition and sensorimotor plasticity when compared with control subjects. CADASIL patients also showed an altered neuropsychological profile. Correlation between sensorimotor plasticity and neuropsychological alterations was observed in CADASIL patients. CONCLUSIONS: These results suggest that acetylcholine and glutamate could be involved in the dementia process in CADASIL and that abnormal sensorimotor plasticity correlates with the neuropsychological profile in CADASIL patients.

The meaning in empathy: distinguishing conceptual encoding from facial mimicry, trait empathy, and attention to emotion.

In order to truly empathise with another, we need to recognise and understand how they feel. Perception-action models of empathy predict that attending to another's emotion will spontaneously activate the observer's own conceptual knowledge for the state, but it is unclear how this activation is related to facial mimicry, trait empathy, or attention to emotion more generally. In the current study, participants did spontaneously encode background facial expressions at a conceptual level even though they were irrelevant to the task (the Emostroop effect; Preston & Stansfield, 2008), but this encoding was not associated with mimicry of the faces, trait empathy, the ability to resolve competing semantic representations (Colour-naming Stroop task), or the tendency to be distracted by emotional information more generally (Intrusive Cognitions task). Our results suggest that trait empathy increases attention to emotional information, but conceptual encoding occurs across individuals as a natural consequence of attended perception.

Gender differences in emotional responses: a psychophysiological study.

Gender differences in emotional responses have been investigated in two groups of students, 22 males and 21 females. Participants watched a set of sixty emotional standardized slides divided into pleasant, neutral and unpleasant, while Startle reflex, Evoked Potentials, Heart Rate, facial EMG and Skin Conductance were recorded. Startle reflex amplitude, an index modulated by amygdala and orbitofrontal cortex and sensitive to aversive emotional stimuli, was overall larger in women. In addition, startle emotion modulation was greater in women with respect to men. Slow Evoked Potentials (400-800 ms), a measure representing the cognitive component of the emotional response, revealed gender differences in the left prefrontal site, with women showing greater positivity to unpleasant compared with pleasant slides while men had greater positivity to pleasant vs. neutral slides. Women, compared with men, perceived all slides as less pleasant and reported greater arousal to unpleasant condition. Results are in line with known functional brain differences, at level of limbic and paralimbic structures, between men and women, and point to biologically grounded greater sensitivity and vulnerability of women to adverse/stressful events.

Cognitive reappraisal and acceptance: an experimental comparison of two emotion regulation strategies.

The purpose of the present study was to compare the effect of cognitive reappraisal and acceptance on subjective distress, physiological reactions and behavioral avoidance in relation to aversive emotional states elicited by film-clips. Ninety-four participants were randomized to one of three groups. The Reappraisal group was instructed to think about what they saw in a way that minimized negative emotional reactions, the Acceptance group was told to let their feelings come and go without trying to control or avoid them, while the Watch (control) group was told just to watch the film-clips. Compared to the control condition, both reappraisal and acceptance led to significant reductions of subjective distress, physiological reactions associated with aversive emotions and behavioral avoidance. On the three types of measures there were few significant differences between the Reappraisal and Acceptance groups, but when such differences existed they were to the benefit of the Reappraisal condition. In the reappraisal condition there was however a positive correlation between elicited aversive emotion and avoidance, while no such correlation existed in the acceptance condition. The results are interpreted and discussed in relation to the theories underlying reappraisal and acceptance as well as the conceptual framework for emotion regulation established by Gross (2007).

Paediatric electromyography in the modern world: a personal view.

Paediatric electromyography (EMG) is an invaluable diagnostic test for the investigation of neuromuscular disease, but its use is inconsistent between and within different countries. One perception is that the procedure is painful; however, in comparison with common investigations performed routinely in children, EMG is better tolerated. While some developments, such as those within clinical genetics, would appear to mark its demise, paradoxically the more genetic abnormalities that are discovered in conditions such as hereditary neuropathy, the more precise a delineation of the phenotype is required. EMG has particular strengths in the diagnosis of neuropathies, motor neuronopathy and neuromuscular transmission disorders such as myasthenia. Also, it can supplement the investigation of myopathies. Areas of development include the diagnosis of myasthenia, delineation of bulbar palsy as a cause of dysphagia, more accurate and earlier prediction of prognosis in neonatal brachial palsy and investigation of channelopathies. It is a valuable diagnostic tool in developed countries and those with limited resources.

The feasibility of hypnotic analgesia in ameliorating pain and anxiety among adults undergoing needle electromyography.

OBJECTIVE: Our hypothesis was that hypnotic analgesia reduces pain and anxiety during electromyography (EMG). DESIGN: We performed a prospective randomized, controlled clinical trial at outpatient electrodiagnostic clinics in teaching hospitals. Just before EMG, 26 subjects were randomized to one of three 20-min audio programs: education about EMG (EDU) (n = 8); hypnotic induction without analgesic suggestion (n = 10); or hypnotic induction with analgesic suggestion (n = 8). The blinded electromyographer provided a posthypnotic suggestion at the start of EMG. After EMG, subjects rated worst and average pain and anxiety using visual analog scales. RESULTS: Mean values for the EDU, hypnotic induction without analgesic suggestion, and hypnotic induction with analgesic suggestion groups were not significantly different (mean +/- SD): worst pain 67 +/- 25, 42 +/- 18, and 49 +/- 30; average pain 35 +/- 26, 27 +/- 14, and 25 +/- 22; and anxiety 44 +/- 41, 42 +/- 23, and 22 +/- 24. When hypnosis groups were merged (n = 18) and compared with the EDU condition (n = 8), average and worst pain and anxiety were less for the hypnosis group than EDU, but this was statistically significant only for worst pain (hypnosis, 46 +/- 24 vs. EDU, 67 +/- 35; P = 0.049) with a 31% average reduction. CONCLUSIONS: A short hypnotic induction seems to reduce worst pain during electromyography.

Infrared reflectance as an alternative to EMG for measuring prepulse inhibition of startle eyeblink.

The "gold standard" measure of the human startle eyeblink response is the ocular electromyogram (EMG). However, EMG measurement is not always feasible, as with special populations or during functional neuroimaging. We evaluated an alternative, nonelectrical, noncontact measure that uses infrared (IR) light reflected from the eye. By simultaneously recording IR and EMG during an acoustic prepulse inhibition of startle paradigm, we were able to directly compare the two measures and evaluate the relative reliability and validity of the IR measure as an index of startle response modulation. Although fewer responses were detected using IR than EMG, both measures were equally sensitive to prepulse modulation of response amplitude, latency, and probability. We conclude that when the goal is simply to assess the effects of a prepulse on the startle response, IR reflectance is an adequate alternative to EMG.

The history of surface electromyography.

The history of muscle pain and dysfunction is viewed through the lens of a four factor theory of histologic (tissue related) issues, psychologic (emotional) issues, sensory motor (movement) issues, and biomechanical (postural) issues. The historical antecedents of surface electromyography are reviewed.

Emotion among women with psychopathy during picture perception.

Emotional reactions in women with psychopathy were examined in a mixed-picture paradigm using psychophysiological measures. Startle probes were presented at 2.0 or 4.5 s following onset of a 6-s picture presentation. At 2.0 s, nonpsychopaths exhibited the typical pattern of eyeblink reflex magnitude: unpleasant > neutral > pleasant. Psychopaths with high general levels of anxiety also exhibited this pattern. Psychopaths with lower anxiety exhibited attenuated reflex magnitudes during unpleasant pictures. Similarly, when focusing on psychopathy components, only individuals expressing high antisocial behavior and high emotional detachment exhibited smaller reflex magnitudes during unpleasant pictures. At 4.5 s, all groups exhibited normal, potentiated reflex magnitudes during unpleasant pictures. Group differences were not observed for other measures.

Synchronizing effect of clock rhythm on the 'when to move' decision in repeated voluntary movements.

In 13 volunteers, surface EEGs from F(z), C(z), C(3), C(4), and P(z) electrodes and EMG from the flexor digitorum communis were recorded during an experimental task in which the performance of wrist flexion was linked with the selection of a clock sound. In the epoch from 4 to 1 s before movement, more than 95% of the records exhibited a small negative shift from the baseline. The position of these shifts on the time axis made it possible to create groups of time trials. The average EEG curves from these groups showed one prominent negative shift from the baseline, which could be related to the position of particular clock sounds. The slope values of these shifts were highest under the F(z) and C(z) electrodes. We suggested that these negative shifts coincided with 'when to move' decisions, which preceded the execution of the movement at varying intervals.