Comparison of three cognitive strategies in altering pain behaviors on a cold pressor task

The efficacy of three cognitive strategies for coping with pain was examined in a cold-water pressor task in a sample of college students. Subjects were pretested and then randomly assigned to one of three treatment conditions (Paradoxical Intention, Rational Self-statement, or Self-observation) or to an expectancy control group. Following training in the respective cognitive strategies, all groups were given a posttest in the cold-water pressor to determine the effectiveness of the treatment. Pain thresholds, tolerances, and discomfort ratings were recorded for subjects in each condition. No differences were found between the Paradoxical Intention or Rational Self-statement groups and the Expectancy Control on any of the pain measures. The Self-observation treatment condition, however, had significantly higher pain tolerance scores than the Expectancy Control group. The findings were attributed to the subjects' dissociating the sensory aspects of the pain experience from the anxiety when focusing upon the coldness and wetness of the cold water.     

Brain stimulation and conscious experience

Libet discovered that a substantial duration (> 0.5-1.0 s) of direct electrical stimulation of the surface of the somatosensory cortex at threshold currents is required before human subjects can report that a conscious somatosensory experience had occurred. Using a reaction time method we confirm that a similarly long stimulation duration at threshold currents is required for activation of elementary visual experiences (phosphenes) in human subjects following stimulation of the surface of the striate cortex. However, the reaction times for the subject to respond to the cessation of the visual experience after the end of electrical stimulation could be as brief as 225-242 ms. We also carried out extensive studies in cats under a variety of anesthetic conditions using the same electrodes and parameters of stimulation employed in the human studies to study the patterns of neuronal activity beneath the stimulating surface electrode. Whereas sufficiently strong currents can activate neurons within milliseconds, stimulating currents close to threshold activate sustained neural activity only after at least 350-500 ms. When currents are close to threshold, some neurons are inhibited for several hundreds of millisecond before the balance between inhibition and excitation shifts towards excitation. These results suggest that the prolonged latencies, i.e., latencies beyond 200-250 ms, for the emergence of conscious experience following direct cortical stimulation result from a delay in the sustained activation of underlying cortical neurons at threshold currents rather than being due to any unusually long duration in central processing time. Intracellular records from cortical neurological cells during repetitive electrical stimulation of the surface of the feline striate cortex demonstrate that such stimulation induces a profound depolarizing shift in membrane potential that may persist after each stimulus train. Such a depolarization is evidence that extracellular K+ concentrations have increased during electrical stimulation. Such an increase in extracellular K+ progressively increases cortical excitability until the threshold for sustained activation of cortical neurons is reached and then exceeded. Consequently, the long latency for threshold activation of cortical neurons depends upon a dynamically increasing cortical facilatory process that begins hundreds of milliseconds before there is sustained activation of such neurons. In some cases, this facilatory process must overcome an initial stimulus-induced inhibition before neuronal firing commences.     

TEMPORAL INTEGRATION OF PERCEPTUAL RESPONSE TO SUPRALIMINAL ELECTRICAL STIMULATION

E kman , G., F röberg , J. & F rankenhaeuser , M. Temporal integration of perceptual response to supraliminal electrical stimulation. Scand. J. Psychol ., 1968, 9, 83–88.—The effect of duration of electrical stimulation on perceived unpleasantness was investigated in 10 subjects. Duration of stimulation ranged from 0.05 to 3.00 sec. Three levels of intensity were investigated representing 2, 3, and 4 times the individual sensation threshold. For all stimulus intensities perceived unpleasantness was a simple logarithmic function of stimulus duration over the whole temporal range. This relation describes the trend of both the group data and the data from most individual subjects. The results support previous findings over a narrower temporal range and agree with results recently obtained in several additional sense modalities.     

A novel radiant heat test for assessing pain threshold in human subjects: Measurement stability

New methodologies to assess analgesic response in humans are needed to better integrate preclinical and clinical data. In the present study we examined the test-retest stability of an innovative radiant heat methodology compared with an electrical stimulation methodology. For the radiant heat task, a modified rodent tail flick apparatus was used. The latency for finger withdrawal was recorded. For the electrical stimulation tasks, subjects placed two fingers on two electrodes from which they received a brief series of increasingly intense electrical stimulations. Maximum stimulus intensity (in milliamps) delivered was recorded. On each of 4 test days, the subjects received five test trials with a 10-min interval between trials. All the subjects were tested twice on each apparatus in a counterbalanced design. Finger withdrawal latencies for the radiant heat task did not differ significantly across test trials or test days. Finger withdrawal scores for electrical stimulation increased significantly across test trials as well as test days. These data show that the radiant heat method generates consistent latencies across trials and days, whereas shock produces trends over time. The radiant heat task, which is convenient to operate and inexpensive to build, appears promising as a reliable test of pain threshold in humans.     

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.     

不同年龄妇科患者痛阈测试及其临床意义

采用双盲、前瞻性研究,选择90例妇科择期全麻下子宫肌瘤剔除或子宫全切手术患者,ASA分级Ⅰ或Ⅱ级,按年龄分两组,中青年组（A组）50例,年龄25岁～50岁,老年组（B组）40例,年龄60岁-80岁,术前使用电刺激测定并记录患者的痛阈和耐痛阈,观察不同年龄妇科患者痛阈和耐痛阈以及两者之间相关性。结果显示A组与B组痛阈分别为（1．86±0．51）mA和（1．89±0．66）mA差异无统计学意义;A组比B组耐痛阈低分别为（6．16±2．53）mA和（8．40士3．21）mA,差异有统计学意史;A组痛阈与耐痛阈之间有相关性（Spearman相关系数为-0．42,P〈0．05）;B组痛阈与耐痛阈之间无相关性。因此,老年患者耐痛阈升高,中青年患者术前痛阈和耐痛闽均可预测术后疼痛,老年患者术前痛阈不能预测术后疼痛。     

A brainstem “mini-discharge” syndrome (anesthesia dolorosa)

Chronic pain consisting of anesthesia dolorosa secondary to bilateral interruption of the trigeminal nerves is presented as a brain stem reticular denervation syndrome. Electrothalamograms revealed fast frequency discharges in the mesothalamic prerubral and centermedian reticular formation. Mesothalamic electrical stimulation attenuated the discharges. Pain and other symptoms presumably of brainstem origin also were attenuated or abolished by therapeutic electrical stimulation twice daily. It is postulated that brain stem-represented behavioral generators are implicated by the reticular discharges in order to produce the complex symptomatology. Consequently the symptom complex is collectively identified as a brainstem “mini-discharge” syndrome. A theoretical discussion is presented to defend the thesis that reticular denervation-induced low threshold discharge system accounts for the episodic states of pain, dyskinesia, mood, and memory disturbances.     

Pain expectation,negative affect,and angry aggression

An experiment was conducted to determine if the relatively strong negative affect generated by anticipation of pain from exposure to aversive stimulation would give rise to an instigation to aggression and accompanying feelings of annoyance-irritation-anger. The 45 undergraduate women in the study were required to immerse their nondominant hand in water as they administered reward and punishment to a fellow student, supposedly as an evaluation of that person's solutions to assigned problems. In two-thirds of the cases the water temperature was unpleasantly cold, while it was much more tolerable in temperature for the remaining subjects. Half of the participants in the cold water condition and all of those in the more tolerable water temperature group has been led to expect the possibility of pain as they kept their hand in the water, whereas the remaining women (exposed to the cold water) had been alerted only to the physical sensations they would have. In accord with the findings obtained in an earlier experiment by Leventhal, Brown, Sacham, and Enquist (1979), the subjects in the cold water group expecting that they might feel pain reported experiencing the greatest discomfort. Further, consistent with Berkowitz's analysis of anger and angry aggression, these participants also reported the strongest feelings of annoyance-irritation-anger and were most punitive to the available target even though they could not attribute their discomfort to this person.     

Threshold tracking for assessment of long-term adaptation and sensitization in pain perception

To assess temporal variations in the perception of "phasic" heat pain stimuli a psychophysical tracking procedure was developed that enables repeated assessment of the pain threshold at short intervals. This "double-tracking" procedure produces two tracking curves simultaneously, one that approaches the pain threshold gradually from above, the other from below. The threshold for phasic heat pain was measured in 80 tracking trials with stimuli at temperatures near the pain threshold. Concurrently, the threshold for "tonic" heat pain was determined after every 20 tracking trials with a stimulus adjustment procedure. Eleven healthy subjects (age: 26.4 yr. +/- 6.0) participated in 2 sessions each. Phasic stimulation near the pain threshold did not produce any trends in either of the two threshold measures. Hence there was no long-term adaptation or sensitization. However, there were random variations (random walks) in the tracking curves, which we interpret as resulting from a stochastic relationship between stimulus and sensation. In agreement with other reports, discrimination seemed to be better at painful than at nonpainful temperatures.     

Underpredicted pain disrupts more than correctly predicted pain, but does not hurt more

One of the explanations for the negative effects of underpredicted aversive experiences is that they have more impact than correctly predicted aversive experiences. In a laboratory experiment 40 normal female subjects executed an auditory discrimination task. Subjects were randomly assigned to a correct information condition and an underprediction information condition. After ten trials (baseline) subjects were informed that they would receive some painful (correct prediction) or non-painful tingling (underprediction) stimuli during the discrimination task. Starting just before five of the following 20 discrimination trials, 2 s of painful electrical stimulation was given. Subjects rated sensations and painfulness of the electrical stimulation, subjective anxiety, and degree of distraction from the task, after each pain stimulus. Reaction times of the discrimination task and heart rate were measured. Underprediction information resulted in lower pain ratings, but stronger heart rate responses and higher disruption on the discrimination task, compared to correct information. This suggests that while underpredictions of pain do not hurt more, disruption on primary tasks and physiological impact are higher. Underpredicted pain has more impact than correctly predicted pain, not because it hurts more, but because it conveys inherent danger information.     

Biomechanical analyses of prolonged handwriting in subjects with and without perceived discomfort

Since wrist-joint position affects finger muscle length and grip strength, we studied its biomechanical relevance in prolonged handwriting. We recruited participants from young adults, aged 18–24, and separated them into control (n = 22) and in-pain (n = 18) groups, based whether or not they experience pain while handwriting. The participants then performed a writing task for 30 min on a computerized system which measured their wrist-joint angle and documented their handwriting kinematics. The in-pain group perceived more soreness and had a less-extended wrist joint, longer on-paper time, and slower stroke velocity compared to control group. There was no significant difference in handwriting speed and quality between the two groups. The wrist extension angle significantly correlated with perceived soreness. Ergonomic and biomechanical analyses provide important information about the handwriting process. Knowledge of pen tip movement kinematics and wrist-joint position can help occupational therapists plan treatment for individuals with handwriting induced pain.     

The influence of preferred coping style and cognitive strategy on laboratory-induced pain.

OBJECTIVE: To evaluate the effects of matching an individual's coping style (low, mixed, or high monitoring) to an appropriate cognitive strategy (distraction or sensation monitoring) to improve pain management. DESIGN: This study used a split-plot factorial design in a laboratory setting. MAIN OUTCOME MEASURES: Main outcomes were pain threshold, pain tolerance, pain intensity, pain affect, and anxiety. RESULTS: The results of the 2 x 3 x 3 (Experimental Condition x Coping Style x Trial) analysis of variance (ANOVA) interaction were significant for pain threshold scores, F(4, 178) = 2.95, p < .01. Low monitors in the matched distraction trial had higher pain threshold scores than during baseline, t(15) = -2.68, p = .017, and the mismatched sensation monitoring trial, t(15) = 2.80, p = .014. High monitors' pain threshold scores were higher than baseline only during the matched sensation monitoring trial, t(27) = -2.75, p = .010. The results of the 2 x 3 x 3 ANOVA interaction were not significant for pain tolerance scores; however, when the mixed monitors were excluded, the 3-way interaction was significant, F(2, 124) = 3.48, p < .05. The results were nonsignificant for pain intensity, pain affect, and anxiety. CONCLUSION: Results demonstrate that matching coping style to the appropriate cognitive strategy is important for improving pain threshold and pain tolerance; however, matching did not reduce pain intensity, pain affect, or anxiety. Future studies should explore the explanation for differential responses of high and low monitors and should test these hypotheses in a clinical setting.     

Mesothalamic discharge in a chronic pain,allergy and fluid retention syndrome (case report)

A 32-year-old woman was bedridden for a year because of chronic pain and headaches. She had insomnia, depression, suicidal thoughts and a severe chemical allergy. She had been on steroid therapy for two years and became Cushingoid with striae in the arm pits, groins and abdomen. However, she had no hypertension, nor the buffalo fat and hirsutism. She was very edematous, with a weight gain from 112 to 180 lbs. The fluid retention did not conform to the syndrome of inappropriate antidiuretic hormone. Studies revealed abnormal scalp EEG discharges and high-voltage seizure discharges in the posterior thalamus. Electrothalamic stimulation suppressed the thalamic discharges and relieved the patient’s pelvic pain and headaches. After one month of several thalamic stimulations per day, she was able to get out of bed and ambulate. In addition, the patient no longer was edematous and was tolerating perfumes and floor detergents. Steroids were progressively reduced without complications of withdrawal. She went from a completely steroid dependent state to independent during the first 1-1/2 yrs of thalamic stimulation. With continued thalamic stimulation she has done well for 8-1/2 yrs, weighs 112 lbs, keeps house and drives a car. It’s speculated the illness is a chronic pain multiple system syndrome predominantly due to mesothalamic discharges and body infirmities. The mesothalamic discharge implicated neural networks, which represent biologic systems, i.e. pain, sleep, fluid retention, etc. Therapeutic stimulation attenuates the discharges and the neural networks return to their normal set points of homeostasis.     

Does humor facilitate coping with physical discomfort?

The mediation of superior coping with physical discomfort after humorous stimulation was explored through respondents' exposure to materials varying markedly in their capacity to evoke amusement and joviality. Both male and female respondents were exposed to (a) stand-up comedy, (b) situation comedy, (c) serious drama, (d) instructional material, or (e) tragedy. Discomfort threshold for cuff pressure at the upper arm was ascertained prior to and following exposure. Cognitive and affective responses to the materials were recorded after the postexposure threshold measurement. Compared against exposure to instructional material in the control condition, and compared against pre-exposure threshold measures, exposure to either type of comedy and, unexpectedly, to tragedy significantly elevated the threshold for physical discomfort in both male and female respondents. Serious drama had no such effect. Taken together, the exposure effects on the discomfort threshold could not be attributed to amusement reactions. Nor could they be considered mediated by responses of positive hedonic quality during and after exposure. There was some indication, however, that the capacity of stimuli to evoke humorous reactions (material being deemed funny) and the absorption potential of stimuli (material being deemed captivating) were positively involved in the mediation of postexposure tolerance of physical discomfort.The authors would like to thank Charles Aust, Rahul Biswas, Ted Jones, and John Owens for their assistance in the data collection and in the planning of this investigation.     

Brain stimulation and conscious experience: electrical stimulation of the cortical surface at a threshold current evokes sustained neuronal activity only after a prolonged latency

Libet demonstrated that a substantial duration (>0.5-1.0 s) of direct electrical stimulation of the surface of a sensory cortex at a threshold or liminal current is required before a subject can experience a percept. Libet and his co-workers originally proposed that the result could be due either to spatial and temporal facilitation of the underlying neurons or additionally to a prolonged central processing time. However, over the next four decades, Libet chose to attribute the prolonged latency for evoking conscious experience to a prolonged central processing time. In my view, Libet has not provided any convincing evidence, either on the basis of his own past work or in his critique of my paper, for his hypothesis of a central processing time exceeding 0.5s before conscious experience emerges following direct electrical threshold stimulation of the cortical surface. I stand by my original results and conclusion that such prolonged latencies are largely the consequence of a dynamically increasing cortical facilitatory process that begins hundreds of milliseconds before there is a sustained neuronal activation. In some cases, the facilitatory process must overcome an initial stimulus-induced inhibition before neuronal firing commences.     

Detection by the guinea pig of acoustic stimulation and of electrical stimulation of the brain

A threshold procedure using operant behavioral techniques with positive reinforcement was developed after initial efforts with avoidance behavioral procedures proved unsatisfactory. In the first of three experiments the operant threshold procedure was tested by determining masked auditory thresholds for trains of clicks. In a second experiment, similar techniques were used to measure thresholds for electrical stimulation of the brain. The last experiment, again an auditory problem, involved a determination of the absolute thresholds for trains of short noise bursts as a function of the time between bursts. Middle ear malfunction proved to be a more severe problem than had been anticipated on the basis of reports in the literature. The threshold procedure, however, seems to be adequate for determination of absolute or masked thresholds with auditory or electrical stimuli.     

Is pain-related fear a predictor of somatosensory hypervigilance in chronic low back pain patients?

Pain-related fear has been found to be associated with increased disability and increased pain perception in patients with chronic low back pain. A possible mechanism by which pain-related fear could lead to increased pain perception is heightened attention to somatosensory sensations. In the present study, chronic pain patients reporting either a high or low level of pain related fear and control participants performed an auditory reaction time task, while occasionally non-painful electrical stimuli--accompanied by threatening instructions--were given to the arm or back. In the primary task condition, participants had to perform the auditory task while ignoring the electrical stimuli. Next, the task was presented under dual task conditions in which participants had to respond both to tones as well as to detection of electrical stimuli. It was hypothesized that for the primary task, high fearful patients would show greater disruption of performance on the auditory task than low fearful patients and controls when stimuli were presented to the back. For the dual task, slower reaction times for the auditory task, in combination with faster detection of electrical stimuli was expected. The hypotheses were not confirmed but patients scoring high on pain-related fear did show an overall increase in reaction time for all conditions of the primary task, with or without simultaneous stimulation. Regression analyses demonstrated that high pain-related fear was associated with increased reaction time to tones both in patients and healthy controls, and that within patients pain-related fear was a better predictor of reaction time to tones than present pain intensity. The findings may be interpreted as showing that patients with elevated levels of pain-related fear habitually attend to somatic sensations, giving less priority to other attention-demanding tasks.     

Some variables affecting dentists' assessment of patients' distress

Dental students estimated the pain distress and discomfort of their patients after patients received a Class II restoration (simple filing). Dentist's estimates of patient pain accounted for 36% of the variance in patient self-report responses. Dentist accuracy was significantly lower, however, for estimates of anxiety and distress. Dentist accuracy was unaffected by patient's degree of self-monitoring. There was a tendency for female dentists to demonstrate greater accuracy than male dentists, but this effect was nonsignificant. In addition, dentists' accuracy in assessing overall patient discomfort was significantly lower in that segment of the treatment procedure that was most stressful for the dentists. This article discusses theoretical explanations for this latter effect.     

Factors associated with perceived exertion and estimated time limit at lactate threshold

The purpose was to identify the most predictive parameters for perceived exertion and estimated time limit responses at the velocity corresponding to the lactate concentration threshold. The former scale concerns the subject's current status (how hard he feels the exercise currently is) whereas the latter scale deals with a subjective prediction of how long the current exercise level can be maintained. Multiple regression equations were developed among physiological, psychological, nutritional, and individual parameters (subjects' characteristics and performances) as independent variables, and perceived exertion or estimated time limit as dependent variables. Independent variables were collected before or during an incremental running field test. 94 regional to national level athletes (47 endurance-trained runners, 11 sprinters, and 36 handball players) participated. Multiple stepwise regression showed that Rating of Perceived Exertion and Estimated Time Limit at the lactate threshold were mainly mediated by factors relative to the performance expressed in percentage of the maximal aerobic velocity. Secondary factors which contribute significantly as perceptual predictors were related to various classes of factors except for psychological factors.