Relationship between self-reported intensity of headache and magnitude of surface EMG

The study was designed to examine the relationship between self-reported intensity of headache and surface EMG. 98 patients, diagnosed by their neurologists with "muscle-contraction headaches" (tension-type headaches) were referred to evaluate their suitability for biofeedback therapy. At the time of examination, they were asked to rate their average headache intensity on a 10-point scale. Surface EMG data were collected to assess actual muscle contraction. Analysis indicated that among patients diagnosed with muscle contraction headache, there is a positive significant correlation between self-reported intensity of headache and actual muscle-contraction. The current data lend support to the hypothesis that the tension in the headaches currently described as "tension-type" may in fact refer to actual muscular tension or contraction.     

Perception and recall of aversive material as a function of personality type

Relationships between personality dimensions of extraversion (E), neuroticism (N), psychoticism (P) and barrier (B) and patterns of psychophysiological responding during exposure to and subsequent recall of aversive and non-aversive material were investigated. Sixteen male volunteers were asked to recall the critical features of 10 film segments containing either neutral or aversive material. Heart rate (HR), skin conductance (SC) and electromyographic (EMG) responses were recorded throughout the session. Analysis showed that during exposure to aversive material, high BE Ss recorded high levels of autonomic responding and low levels of muscle tension, while during recall, they showed reduced autonomic activity and significantly higher levels of muscle tension. Low BE Ss showed significantly higher levels of muscle tension during film presentation and significantly lower levels during recall, with little change in autonomic reactivity between treatments. Recall data indicate that high BE Ss had significantly better recall under all conditions. N and P differences were unrelated to patterns of psychophysiological responding or efficiency of recall.     

Effects of time uncertainty and instructed muscle tension on fractionated reaction time

Abstract: An experiment was conducted to examine the effects of time uncertainty and instructed muscle tension on the reaction time of elbow flexion. Twenty-two right-handed subjects were asked to respond to an audio stimulus by flexing their right elbow under four conditions (2 time uncertainty × 2 instructed muscle tension). Electromyograms (EMGs) were recorded from the biceps and triceps on the subject's right side. Reaction time was divided into premotor time and motor time, based on the difference between the EMG and elbow flexion response. Analysis of reaction time showed that the effects of time uncertainty and instructed muscle tension were additive. Time uncertainty affected premotor time only, and instructed muscle tension affected motor time only. These results are discussed in terms of the assumption that premotor time is a reflection of the central nervous system and motor time is a reflection to the peripheral muscle system.     

Autonomic and skeletal muscle responses to nonelectrical cutaneous stimulation

Cutaneous stimulation has had a long history as a method of pain control. While there is general agreement that modern techniques such as electrical stimulation and massage often provide relief from acute pain and may in some cases significantly affect chronic pain, the mechanism by which these techniques affect pain remains unclear. Significant attention has been focused on the effects of stimulation on the autonomic nervous system (ANS) along with the increasing evidence of important ANS modulation of nociceptive activity throughout the pain pathway. However, inconsistent results on the presence and direction of ANS changes from cutaneous stimulation characterize the recent literature. The present study investigated a nonelectrical cutaneous stimulation device, the Dermapoints Massageroller, as well as an active placebo massage. The results indicate that the Dermapoints Massageroller has both general effects associated with simple skin stimulation (such as increased skin temperature), as well as specific effects from increased stimulation by the toothed design of the roller. These specific effects include decreased muscle tension (at least for some muscle sites) and increased sympathetic activation. The results are consistent with a model of activation of Pacinian receptors as a possible mechanism for the antinociceptive properties of cutaneous stimulation.     

The role of muscle tension in “repression”

Using an active partial avoidance conditioning paradigm, muscle tension was conditioned to a verbal conditional stimulus (CS), and recall of words semantically unrelated and related to the CS was tested under conditions of three levels of induced muscle tension with 20 subjects (Ss). Results showed the expected decrease in latency of response with moderate tension for all stimuli during the pretreatment period and for the unrelated words during the posttreatment period and a significant increase in latency of response for the related words during the posttreatment period. It is suggested that if the level of muscle tension associated with the conditional response (CR) is induced in Ss, then recall of CS-related material will be inhibited or “repressed.”     

Emotional responding following experimental manipulation of facial electromyographic activity

Increases in zygomatic electromyographic (EMG) responding have been reported during the imagination of positive affective scenes, and increases in corrugator EMG have been reported during negative affective scenes. Thirty female subjects were instructed to imagine three positive affective scenes and three negative affective scenes. During the initial imagination of each scene, the subject was told simply to imagine the situation. The subject then imagined the situation again and was instructed to enhance the muscle tension in one of two muscle groups (the zygomatic muscles for positive scenes and the corrugator muscle for negative scenes). The subject then imagined the scence a third time and was instructed to suppress the muscle tension in the same muscle group. The order of administration of enhancement and suppression trials was randomized for each scene. Subjects were given several trials to practice controlling both zygomatic and corrugator EMG. Feedback was available during the practice trials and during the enhancement and suppression trials of the experiment. Continuous monitoring of both zygomatic and corrugator EMG during the study indicated that subjects were successful in altering muscle tension in accord with the experimental instructions, and videotapes of subjects' faces indicated no overt changes in facial responding during imagination of the scenes. Subjects' ratings of emotional responding during each scene indicated that subjects experienced less enjoyment and more distress during positive affective trials in which they suppressed zygomatic EMG activity. The results are discussed in terms of the facial feedback hypothesis.     

Muscle tension in human operant heart rate conditioning

The physiological mechanism involved in human operant heart rate conditioning is not known. If skeletal muscle tension is a mediator, it should be possible to generate significant heart rate increases by inconspicuous voluntary muscle tension. Eleven subjects were instructed to generate inconspicuous muscle tension for 90-second periods. No gross muscle movements were observed, but average heart rate during the trials was over 13 beats-per-minute greater than pre-trial base lines. Respiratory pattern changes and surface electromyogram changes did not reliably correlate with heart rate increases. Inconspicuous muscle tension could be a mediator in human operant heart rate conditioning, and cannot be ruled out by absence of change in respiratory pattern or electromyogram.     

The role of physiological attention-focusing in the relaxation treatment of sleep disturbance,general tension,and specific stress reaction

Three experiments comparing the effects of muscle tension-release relaxation with vs without physiological attention-focusing and no-treatment on (a) sleep disturbance, (b) general tension, and (c) a variety of time estimation, heart rate perception, and stress reaction measures, are reported. The two relaxation conditions produced equivalent reductions in latency to sleep onset reports, suggesting the importance of tension-release in the relaxation treatment of sleep disturbance. Relaxation without physiological attention-focusing was unexpectedly superior to the other relaxation condition in reducing reported daily tension, supporting Denny's (1976) hypothesis that pervasive anxiety may be a function of anxiety conditioned to relaxation-produced cues. Sleep disturbed subjects over-estimated elapsed time, and relaxation training improved accuracy of time estimation. Several additional differences between sleep and tension subjects and among the three treatment conditions on physiological activity during stress are reported and discussed.     

Phase-dependent compensatory responses to perturbation applied during walking in humans

The interaction between the peripheral and the central regulation of locomotion was studied by examining the dependency of the response to unexpected perturbation on the phase of the step cycle. The changes in the latency and magnitude of various muscle responses to electrical stimulation of the toe and applied unexpectedly at different phases of the locomotor cycle in humans are described. The results show that response to perturbation is gated and modulated in both ipsi- and contralateral limb muscles. These muscle responses, when present, were always excitatory in nature. They were not correlated with the normal locomotor activity, thus suggesting a more complex organization of the response. Except for one muscle in the contralateral limb, the latency of the other muscle responses did not vary across the step cycle. in response to the perturbation, the appropriate phase of the step cycle was shortened. The results from this study suggest that the perturbation applied elicits a phase-independent, normal ipsilateral flexor response in the tibialis anterior muscle, while the gating and modulation of other ipsi- and contralateral muscles provide appropriate phase-dependent adaptive response to maintain postural stability and continue with the ongoing task of locomotion.     

Shoulder Muscle Activity Dampens Arm Swing Motion When Altering Upper Limb Mass Characteristics During Locomotion

Weighting the arms during locomotion results in decreased swing motion and increased shoulder muscle activity. To determine the functional relevance of this activity, participants walked on a treadmill with the arms unweighted, or weighted unilaterally or bilaterally. Similar to past work, the weighted arms decreased in swing amplitude and increased their shoulder muscle activity. A close examination of shoulder muscle activities in specific regions of the arm swing cycle suggested these muscles primarily acted eccentrically for all weighting conditions. These findings suggest that the increased shoulder muscle activities when weighting the arms act to dampen the arms when the inertial characteristics of the arms are altered, as opposed to assisting in driving swing of the heavier arms.     

Pre-Motor and Motor Reaction Time Differences Associated with Stretching of the Hamstring Muscles

Pre-motor and motor RT scores were obtained from 24 male Ss using a knee flexion task. It was predicted that an increased arousal state due to proprioceptive feedback from stretched hamstring muscles would shorten pre-motor RT while motor RT would shorten because of changes in muscle tension development due to changes in the series elastic and/or contractile components of the muscle tissue. A finger RT task was also included in order to determine whether other factors not related to changes in the stretch of the hamstring muscles were operative. Motor RT decreased with increased muscle stretch and constituted 46% of leg RT. Pre-motor RT as well as finger RT increased rather than decreased with increased muscle stretch. No relationship was found between pre-motor and motor RT indicating that lags in CNS processing are independent of lags associated with the rate of muscular tension development.     

Interaction of afferent and efferent signals underlying joint position sense: empirical and theoretical approaches

A model of joint position sense is considered based on the concept that central motor commands are adequately expressed in terms of shifts of the so-called invariant length-tension characteristics for agonist and antagonist muscles. The main points of this concept are discussed to clarify them and to prevent misunderstanding. The basic idea of the model is that the efferent copy of the central motor commands plays the role of a reference frame for evaluation of afferent proprioceptive discharges. An experiment with reproduction of constrained movements was performed in order to investigate the influence of voluntary flexor or extensor muscle tension on position sense in the elbow joint. The results demonstrate adequate perception of joint position on the background of voluntary muscle tension and thus are quite consistent with the model. The role of afferent and efferent signals in position sense is discussed with special reference to views expressed recently by different authors. The interrelation between position sense and sense of effort is considered, based on a concept of senso-motor space.     

Interaction of Afferent and Efferent Signals Underlying Joint Position Sense

A model of joint position sense is considered based on the concept that central motor commands are adequately expressed in terms of shifts of the so-called invariant length-tension characteristics for agonist and antagonist muscles. The main points of this concept are discussed to clarify them and to prevent misunderstanding. The basic idea of the model is that the efferent copy of the central motor commands plays the role of a reference frame for evaluation of afferent proprioceptive discharges. An experiment with reproduction of constrained movements was performed in order to investigate the influence of voluntary flexor or extensor muscle tension on position sense in the elbow joint. The results demonstrate adequate perception of joint position on the background of voluntary muscle tension and thus are quite consistent with the model. The role of afferent and efferent signals in position sense is discussed with special reference to views expressed recently by different authors. The interrelation between position sense and sense of effort is considered, based on a concept of senso-motor space.     

Phase-Dependent Compensatory Responses to Perturbation Applied During Walking in Humans

The interaction between the peripheral and the central regulation of locomotion was studied by examining the dependency of the response to unexpected perturbation on the phase of the step cycle. The changes in the latency and magnitude of various muscle responses to electrical stimulation of the toe applied unexpectedly at different phases of the locomotor cycle in humans are described. The results show that response to perturbation is gated and modulated in both ipsi-and contralateral limb muscles. These muscle responses, when present, were always excitatory in nature. They were not correlated with the normal locomotor activity, thus suggesting a more complex organization of the response. Except for one muscle in the contralateral limb, the latency of the other muscle responses did not vary across the step cycle. In response to the perturbation, the appropriate phase of the step cycle was shortened. The results from this study suggest that the perturbation applied elicits a phase-independent, normal ipsilateral flexor response in the tibialis anterior muscle, while the gating and modulation of other ipsi-and contralateral muscles provide appropriate phase-dependent adaptive response to maintain postural stability and continue with the ongoing task of locomotion.     

Physiologic and self-report comparisons between tension headache sufferers and nonheadache controls

Tension headache sufferers and nonheadache controls were compared with respect to (1) frontal EMG during both baseline and presentation of an imagined stressor, (2) trait anxiety, (3) locus of control expectancies for health related behaviors, and (4) exposure to stressful life events. Tension headache sufferers displayed higher resting muscle tension levels than did nonheadache controls. However, both groups responded similarly to the imagined stress stimulus and displayed significant muscle tension elevations of similar magnitude. While tension headache sufferers reported higher levels of trait anxiety, no differences were found between the two groups for locus of control expectancies and exposure to stressful life events. The diagnostic and treatment implications of these findings are discussed.     

Synchronized neuronal oscillations and their role in motor processes

Recant data on the relationship of brain rhythms and the simultaneous oscillatory discharge of single units to motor preparation and performance have largely come from monkey and human studies and have failed to converge on a function. However, when these data are viewed in the context of older data from cats and rodents, some consistent patterns begin to emerge. Synchronous oscillatory activity, at any frequency, may be an integrative sensorimotor mechanism for gathering information that can be used to guide subsequent motor actions. There is also considerable evidence that brain rhythms can entrain motor unit activity. It is not clear yet whether the latter influence is a means of organizing muscle phase relationships within motor acts, or is simply a 'test pulse' strategy for checking current muscle conditions. Moreover, although the traditional association of faster brain rhythms with higher levels of arousal remains valid, arousal levels are correlated so tightly with the dynamics of sensorimotor control that it may not be possible to dissociate the two.     

Salience, induced muscle tension, and the ability to ignore irrelevant information

Two experiments are described that examined the effects of salience and induced muscle tension on subjects' ability to ignore irrelevant information in card sorting tasks. The results of the first experiment suggested that even though the responses appropriate to the relevant and irrelevant information were unrelated there was an effect of irrelevant information, but only when it was more salient than the relevant information. Induced muscle tension was found to improve performance based on less salient attributes but to degrade performance based on more salient attributes. The second experiment confirmed this latter finding using a version of the Stroop test. It is tentatively suggested that induced muscle tension may inhibit naming responses.     

Cocaine-induced brainstem seizures and behavior.

A variety of abnormal sensory/motor behaviors associated with electrical discharges recorded from the bilateral brainstem were induced in adult WKY rats by mechanical (electrode implants) and DC electrical current stimulations and by acute and chronic administration of cocaine. The electrode implant implicated one side or the other of the reticular system of the brainstem but subjects were not incapacitated by the stimulations. Cocaine (40 mg/kg) was injected subcutaneously for an acute experiment and subsequent 20 mg/kg doses twice daily for 3 days in a chronic study. Cocaine generated more abnormal behaviors in the brainstem perturbation group, especially the electrically perturbated subjects. The abnormal behaviors were yawning, retrocollis, hyperactivity, hypersensitivity, "beating drum" behavior, squealing, head bobbing, circling, sniffing, abnormal posturing, and facial twitching. Shifts in the power frequency spectra of the discharge patterns were noted between quiet and pacing behavioral states. Hypersensitivity to various auditory, tactile, and visual stimulation was present and shifts in the brainstem ambient power spectral frequency occurred in response to tactile stimulation. These findings suggest that the brainstem generates and propagates pathological discharges that can be elicited by mechanical and DC electrical perturbation. Cocaine was found to activate the discharge system and thus induce abnormal behaviors that are generated at the discharge site and at distant sites to which the discharge propagates. Cognitive functions may also be involved since dopaminergic and serotonergic cellular elements at the brainstem level are also implicated.     

A system for providing tactile EMG biofeedback

This report describes a flexible and inexpensive biofeedback system for providing discrete pulses against the skin surface at a frequency proportional to the level of activity from selected muscle groups. The primary components consist of a voltage controlled pulse generator and a tactile transducer. Other system capabilities include the production of digital information for recording devices and the providing of pulsed auditory EMG biofeedback. The system may be particularly applicable for the experimental reduction of psychological and muscle tension.     

Synergistic influences of sensory and central stimuli on non-voluntary rhythmic arm movements

In recent years, neuromodulation of the cervical spinal circuitry has become an area of interest for investigating rhythmogenesis of the human spinal cord and interaction between cervical and lumbosacral circuitries, given the involvement of rhythmic arm muscle activity in many locomotor tasks. We have previously shown that arm muscle vibrostimulation can elicit non-voluntary upper limb oscillations in unloading body conditions. Here we investigated the excitability of the cervical spinal circuitry by applying different peripheral and central stimuli in healthy humans. The rationale for applying combined stimuli is that the efficiency of only one stimulus is generally limited. We found that low-intensity electrical stimulation of the superficial arm median nerve can evoke rhythmic arm movements. Furthermore, the movements were enhanced by additional peripheral stimuli (e.g., arm muscle vibration, head turns or passive rhythmic leg movements). Finally, low-frequency transcranial magnetic stimulation of the motor cortex significantly facilitated rhythmogenesis. The findings are discussed in the general framework of a brain-spinal interface for developing adaptive central pattern generator-modulating therapies.