The reliability of an extrapolated measure of an aversive threshold of pain from radiant stimulation

The relationship between the logarithm of pain threshold latency (sec) and the logarithm of the stimulus intensity (mcal/cm²/sec) has been shown to be linear, and the extrapolated x-intercept value of the linear equation could be a useful measure in pain research. In order to assess the reliability of the x-intercept, pain latency thresholds, were obtained from 23 Ss by utilizing the D’Amour-Smith modification of the dolorimetric technique and by testing under a variety of conditions at each of four stimulus intensities. The empirically determined log t (sec) values were shown to be slightly, but significantly, higher when stimulation was applied to either the dominant limb or to the legs rather than to the nondominant limb or to the arms. The computed slope and x-intercept values did not differ between limbs or between dominant and nondominant sides. None of the three measures changed significantly between the two sessions. The x-intercept value was interpreted as an index of a threshold of aversion and its meaning and applicability were discussed.     

Rhesus monkey (Macaca mulatta) cool sensitivity measured by a signal detection method

Two rhesus monkeys were trained to detect cool stimuli (decrements in skin temperature from the adapted temperature) presented to the palm of the left hand after the skin had been preadapted to a 33°C temperature. The procedure was analogous to the signal detection “yes-no” method used with human observers. Receiver operating characteristic curves were generated by varying the a priori probability of stimulus oecurrence. The proportion of hits and of false alarms increased with increases in the a priori probability of stimulation. The points of isosensitivity of both subjects for cool intensities of 0.3°C, but not at greater intensities, yielded straight lines with slopes of approximately one when plotted on normal-normal coordinates. The values of the d’_s detectability index decreased from 3.52 to 0.75 for one subject and from 2.81 1to 1.28 for the other as the stimulus intensity was decreased from 0.8° to 0.15° cooling from the adapting temperature. Cool thresholds for each subject of 0.19° and 0.12°C were computed from classical psychometric functions when threshold was defined as 50% hits at a 50% probability of stimulus occurrence. These thresholds are comparable to published reports of the cool threshold for the rhesus.     

Human responses to various conditions of water temperature

Skin-surface temperatures on thehuman hand were obtained immediately following six exposure times ranging from 5 to 60 sec. for water temperatures varying in 5° increments from 10° to 40°C. The surface of the skin was found to respond rapidly and regularly to both the temperature and time of exposure. In a second study 30 Ss exposed a hand for 5 or 30 sec. to water temperatures ranging from 10° to 45°C. and made ratings on scales of pain and comfort as well as attaching a verbal label (cold, cool, tepid, etc.) to each experience. The experience of cold became more intense over these time intervals while the experience of warmth became less, and with the threshold constant taken into account the sensations of pain and discomfort were found to follow a psychophysical power law. The usefulness of these sorts of data for interpreting the effects of noxious stimuli in basic learning studies is discussed.     

Psychophysical features of the transition from pure heat perception to heat pain perception

The psychophysical features of the transition from the pure heat to the heat pain range were studied in 25 healthy subjects (mean age 28.8 years). Thirty short heat stimuli from ?1.6° C to + 1.6° C relative to the pain threshold were applied to the thenar of the left hand with an apparatus containing a Peltier thermode (nine different temperatures at 0.4°C intervals). The subjects rated the sensation intensity on a visual analogue scale. The resulting stimulus/sensation intensity relations could be explained equally well (same goodness of fit) by a model with a power function (PF) and by a model with two linear regression lines (TLR), one for stimulus intensities below and one for those above the pain threshold and intersecting at the pain threshold. The slopes of the TLR model were significantly larger above the pain threshold than below it. The PF model produced exponents between 1.8 and 1.9. We conclude that to describe the transition area, it is sufficient to use simple linear models for both the pure heat and the heat pain ranges.     

Developmental changes in infants' sensitivity to octave-band noises

Localization responses to octave-band noises with center frequencies at 200, 400, 1000, 2000, 4000, and 10,000 Hz were obtained from infants 6, 12, and 18 months of age. During an experimental trial, an octave-band noise was presented on one of two speakers located 45° to each side of the infant. A head turn to the noise (correct response) was rewarded by activating an animated toy on top of the speaker. The intensity of the noise was varied over trials (method of constant stimuli) to determine thresholds at each center frequency. Thresholds for the lower frequencies were approximately 5–8 db higher in the 6-month-old infants compared to the older infants. However, there were no consistent differences among groups at the higher frequencies. Infant thresholds were found to be 20–30 db higher than adult thresholds at the lower frequencies. At the higher frequencies thresholds for infants were approaching those of adults.     

The effect of situation-evoked anxiety and gender on pain report using the cold pressor test

The aims of the present study were to investigate the influence of anxiety on pain perception and to test whether gender differences in pain perception are anxiety dependent. Sixty male and female university students exposed to situation-evoked anxiety or a control procedure were measured for their pain threshold, tolerance, and perceived intensity during a cold pressor test. Both subjective and autonomic responses indicated that anxiety was successfully induced in participants exposed to the anxiety condition. Increased situational anxiety had no significant effect on pain threshold or pain tolerance. Significant increases in pain intensity were found for the anxiety group. Levels of anxiety, however, did not correlate with this increased intensity, raising doubt as to the role of anxiety in producing this effect. No gender differences were found for pain tolerance or pain intensity. Gender differences were found for pain threshold in the anxiety group with, contrary to past findings, females showing significantly higher pain thresholds than males. The results are discussed in the light of related studies.     

Increment detection thresholds during binocular rivalry suppression

In two experiments, two-choice forced-choice duration thresholds for increment test flashes were estimated during phases of rivalry suppression and nonsuppression and for a nonrivalry monocular control condition. In both experiments thresholds of both eyes of each S were measured and, to maximize correct detections, feedback was given after every trial and Ss were relieved of the task of continually reporting changes in rivalry phases. Results of both experiments support the conclusion that suppression constitutes an elevation in threshold, on the order of .5 log units relative to thresholds found during nonsuppression and monocular conditions. These data, in concert with others, reinforce the general conclusion that rivalry suppression is an inhibitory state that nonselectively attenuates all classes of inputs falling within the spatial boundaries of the suppressed target.     

Directional sensitivity to a tactile point stimulus moving across the fingerpad

The ability of subjects to discriminate between directions of a point contact moving across the fingerpad was examined. Subjects were required to report, using an adaptive two-interval, two-alternative forced-choice procedure, whether in two sequential stimuli the direction of motion changed in a clockwise or counterclockwise direction. The overall mean orientation-change threshold across eight stimulus orientations was approximately 14°, with the lowest threshold for the point motion toward the wrist. This observed lower threshold in the distal-to-proximal direction is thought to be due to stretching of the skin at the tip of the fingernail, to which one may be particularly sensitive. For all orientations, thresholds were generally more uniform and higher than those reported on vibrotactile linear contactor arrays for horizontal and vertical orientations.     

The discrimination of heading from optic flow is not retinally invariant

Three experiments were conducted to determine whether the discrimination of heading from optic flow is retinally invariant and to determine the importance of acuity in accounting for heading eccentricity effects. In the first experiment, observers were presented with radial flow fields simulating forward translation through a three-dimensional volume of dots. The flow fields subtended 10° of visual angle and were presented at 0°, 10°, 20°, and 40° of retinal eccentricity. The observers were asked to indicate whether the simulated movement was to the right or the left of a target that appeared at the end of the display sequence. Eye movements were monitored with an electrooculogram apparatus. In a second experiment, static acuity thresholds were derived for each of the observers at the same retinal eccentricities. There was a significant increase in heading detection thresholds with retinal eccentricity (from 0.92° at 0° retinal eccentricity to 3.47° at 40°). An analysis of covariance indicated that the variation in sensitivity to radial flow, as a function of retinal eccentricity, is independent of acuity. Similar results were obtained when the Vernier acuity of observers was measured. These results suggest that the discrimination of heading from radial flow is not retinally invariant.     

Comparison of detection threshold values determined using glass sniff bottles and plastic squeeze bottles

Olfactory threshold measures are influenced by such factors as odorant species, diluent type, psychophysical paradigm, and stimulus-presentation procedure. In this study, we compared phenyl ethyl alcohol odor-detection thresholds obtained using 120-ml glass sniff bottles to those obtained using 120-ml plastic squeeze bottles. Although these presentation media are commonly employed in published studies, there has never been a formal comparison of values obtained using them. 10 male and 10 female subjects were tested on two threshold test sessions, one for each type of bottle. Order of sessions was systematically counterbalanced and completed on the same day for a given subject, with a minimum of 30 min. elapsing between sessions. A seven-reversal, single-staircase threshold procedure was employed. Although the threshold values were similar for the two procedures, slightly lower thresholds were obtained using the glass sniff bottles [respective M (SEM) log vol/vol values = -6.61 (.20) and -6.13 (.24)]. These data suggest that, while threshold values using these two presentation procedures can be roughly compared across studies, accurate comparisons may require a slight mathematical adjustment.     

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.     

Gustatory,salivary, and oral thermal responses to solutions of sodium chloride at four temperatures

Using eight highly trained Ss, sensitivity to near threshold levels of NaCl was significantly greater at solution temperatures of 22° and 37°C than at 0° or 55°C. Perceived intensity increased linearly with concentration (0.04%–0.64% NaCl) at all four solution temperatures, with the two lower considered slightly more intense than the two higher temperatures. Biomodal distributions were obtained for hedonic judgments at all temperatures, with three Ss showing greater liking and five Ss showing greater disliking of increasing concentrations. Parotid salivary flow was inversely related to the taste sensitivity, i.e., significantly lower flow rates were obtained for the intermediate than for the hot or cold solutions, independent of salt content. When solution temperature was O°C, the minimum temperature of the oral cavity was 9°–20°C; when solution temperature was 55°C, the maximum temperature of the oral cavity was46°–49°C.     

Is the Effect of Behavioral Synchrony on Cooperative Behavior Mediated by Pain Threshold?

Synchronized behavior results in a variety of prosocial behaviors. Research has also implicated that interpersonal synchrony affects pain thresholds, inferred as indicative of endorphin levels. The current study was designed to see if these pain threshold effects mediated the effect of synchrony on interpersonal cooperation. Twenty six individuals were randomly assigned to complete a 30 minute run on a treadmill in either a synchronized or nonsynchronized condition. Pain threshold was measured both before and after exercise as an indicator of endorphin activity. A postrun social investment game measured interpersonal cooperation. Analyses showed that there was a significant direct relationship between condition and cooperation but that this effect was not mediated by pain threshold.     

Extent-of-motion thresholds under subject-relative and object-relative conditions

The experiment was designed to discover the threshold extent of motion at medium speeds amounting to 41, 82, and 164 min./sec., and to compare the perception of motion arising from subject-relative displacement with the perception of motion arising from object-relative displacement. Extent thresholds were found while velocity was kept constant. Different groups of ten Ss were used for each displacement velocity, and for each S the extent threshold was twice obtained by the method of constant stimuli, once under subjectrelative and once under object-relative displacement conditions. Sensitivity to brief displacements of a continuously visible target was high; average thresholds ranged from 1.0 to 4.4 min. under the various conditions employed. The thresholds were higher for subject-relative conditions and the slower displacement velocities and lower for objectrelative conditions and faster displacements.     

Extent-of-motion thresholds under subject-relative and object-relative conditions

The experiment was designed to discover the threshold extent of motion at medium speeds amounting to 41, 82, and 164 min./sec., and to compare the perception of motion arising from subject-relative displacement with the perception of motion arising from object-relative displacement. Extent thresholds were found while velocity was kept constant. Different groups of ten Ss were used for each displacement velocity, and for each S the extent threshold was twice obtained by the method of constant stimuli, once under subjectrelative and once under object-relative displacement conditions. Sensitivity to brief displacements of a continuously visible target was high; average thresholds ranged from 1.0 to 4.4 min. under the various conditions employed. The thresholds were higher for subject-relative conditions and the slower displacement velocities and lower for objectrelative conditions and faster displacements.     

Pain thresholds,pain-induced frontal alpha activity and pain-related evoked potentials are associated with antisocial behavior and aggressiveness in athletes

ObjectivesDeficiencies in perceptual and cognitive functions have been linked with antisocial and aggressive behavior. To test whether these putative relationships generalize to sport – a context where such behavior is common – we determined the extent to which pain thresholds and cortical activity in response to painful electrical stimulation were associated with antisocial and aggressive behavior in sport; we also examined their link to moral disengagement.DesignA cross-sectional design was used.MethodNinety-four participants completed questionnaires, had their pain threshold determined, and then had their central and frontal pain-related cortical activity recorded while they were electrically stimulated at supra-threshold intensity.ResultsSubjective pain thresholds were positively related while pain induced frontal alpha power was negatively related to antisocial behavior and aggressiveness. Central pain evoked potential amplitudes were negatively related to aggressiveness and moral disengagement.ConclusionsSensitivity to and cortical processing of noxious stimuli were reduced in individuals who more frequently behave antisocially and aggressively when playing sport and who are more likely to use psychosocial maneuvers to justify their harmful behavior. Our findings reveal that pain-related deficits are a feature of individuals who engage in more frequent antisocial and aggressive behavior in the context of sport.     

Movement detection thresholds and stimulus duration

Movement detection thresholds were measured for varying exposures of a moving spot. A tradeoff was found in which an increase in duration (T) was offset by a decrease in the velocity required for detection (V). In the range of durations studied (about 50–700 msec), V × T was constant. The V × T constancy was interpreted in terms of the direct detection of movement as motion, and a comparison was made with Bloch’s law.     

Frequency selectivity using tonal-temporal masking: Diotic vs. dichotic masking

A combined forward-backward masking procedure was used to investigate the threshold of a 30-msec, 500-Hz signal as a function of masker frequency. The signal thresholds were obtained in two signal conditions, diotic (So) and dichotic (S_π), and for two different temporal separations of the maskers. The maskers were 500 msec in duration and were presented at 75 dB SPL. The function relating masked signal threshold to masker frequency was used to describe frequency selectivity in the four conditions. There were no differences in frequency selectivity measured between the diotic and dichotic signal conditions and only a small difference measured between the two intermasker interval conditions. The S_π conditions yielded lower thresholds than did the So conditions. The change in intermasker interval from 10 to 50 msec lowered the threshold maximally 18 dB for the So condition and 13 dB for the S_π condition. The results indicate that in this tonal temporal masking procedure there are no differences between the diotic and dichotic critical bands.     

Comparison of sensitivity of psychophysical and electrophysiological measures of scotopic thresholds in the vicinity of the blind spot

A section of the blind spot was mapped by obtaining detection and averaged EEG threshold measurements using three stimulus light intensities. It was found that averaged EEG and detection measures of the blind spot were equally sensitive when the two highest stimulus intensities were used, although more observations of the stimulus were required with averaged EEG. Detection thresholds were superior to averaged EEG measures with the dimmest stimulus.

     

Shock-induced hyperalgesia: IV. Generality

Brief-moderate shock (3, 0.75 s, 1.0 mA) has opposite effects on different measures of pain, inducing antinociception on the tail-flick test while lowering vocalization thresholds to shock and heat (hyperalgesia) and enhancing fear conditioned by a gridshock unconditioned stimulus (US). This study examined the generality of shock-induced hyperalgesia under a range of conditions and explored parallels to sensitized startle. Reduced vocalization thresholds to shock and antinociception emerged at a similar shock intensity. Severe shocks (3, 25 s, 1.0 mA or 3, 2 s, 3.0 mA) lowered vocalization threshold to shock but increased vocalization and motor thresholds to heat and undermined fear conditioned by a gridshock or a startling tone US. All shock schedules facilitated startle, but only brief-moderate shock inflated fear conditioning. The findings suggest that brief-moderate shock enhances the affective impact of aversive stimuli, whereas severe shocks attenuate pain.