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The term sensation luminance is proposed when light measures are made which depend on individual observer's spectral sensitivity. The unit of measure for sensation luminance is ives/m2. When sensation luminance is used to calculate retinal illuminance the term sensation trolands is proposed.
The aim of this study was to investigate the topographical distribution of chemosensory event-related potentials in relation to stimulation with nicotine. The recognition thresholds of 3 different sensations elicited by nicotine (odor, burning, stinging) were determined. Subsequently, 3 concentrations of nicotine were applied which were just above mean threshold for each of the 3 sensations. Subjects rated the intensity of odor, burning, and stinging. Additionally, they tracked the time course of these sensations. Odor and stinging appeared immediately after stimulus onset. Burning started after several seconds. Intensity ratings of burning and stinging increased with rising stimulus concentrations, whereas the odorous sensation was strongest at medium concentrations. After low and medium stimuli largest mean amplitudes were parietally obtained, whereas following stimulation with the highest concentration, amplitudes peaked at Cz.
The effect of a conditioning bradykinin application on histamine induced excitation of cutaneous nociceptors and on histamine induced sensations of volunteers was studied. Using an in vitro skin nerve preparation, unmyelinated polymodal nociceptor units of rats (n = 11) were tested by bathing their receptive fields from the corium side with 10(-5) M solutions of bradykinin and histamine. Following bradykinin superfusion the histamine induced discharges were enhanced, and previously unresponsive units were excited by histamine. Corresponding psychophysical experiments were carried out in 13 healthy volunteers. Histamine iontophoresis (30 mC) induced predominantly itching sensations after an intracutaneous control injection of physiological saline. However, following bradykinin injections (100 microliters of a 10(-7) M solution) histamine induced little itch but rather a burning sensation lasting 1-2 min. Itching remained suppressed even after the burning sensations had subsided. These data support a hypothesis according to which itching is mediated by a sub-population of polymodal nociceptor units, and pain is induced whenever a larger nociceptor population is recruited. In the CNS itch processing is either occluded (masked) by pain processing, or suppressed by inhibitory processes.
The effect of stimulus duration and frequency on subjective sensations evoked by electrical tooth stimulation was studied in 12 subjects. The sensory responses were classified using 5 equi-sensation categories (perception threshold, prepain, pain threshold, moderate pain, intense pain). Both continuously increasing and randomised stimuli were applied. A comparison was made with the activation thresholds of intradental A- and C-fibres in the cat. The mean threshold of intradental A-fibres was lower than the perception threshold at all pulse durations. Perception threshold decreased with increasing stimulus frequency. Current intensities which evoked prepain at a stimulus frequency of 1 Hz were rated as pain at 20 Hz. At supraliminal pain levels the effects of summation were more marked. High-frequency stimulation produced intense pain sensations at intensities well below the activation thresholds of pulpal C-fibres in the cat. We conclude that both perception and pain thresholds and supraliminal pain are modified by temporal summation, and that activation of different pulpal fibre populations is not responsible for production of prepain and pain sensations.
Afferent impulse frequency, one of the determinants of subjective magnitude of sensation, varies with the rate of rise of stimulus intensity: the faster the increase in stimulus energy, the higher the frequency of firing for a given amount of energy. This predicts that the steeper the stimulus ramp the lower will be the threshold for perception. While such inverse relation holds for myelinated fibre mediated cold sensation and mechanical pressure sensation, the opposite has been reported for unmyelinated fibre mediated heat pain and cold pain sensations. These paradoxical results intuitively suggest possible reaction time artefact. Indeed, a fixed time interval that includes conduction of the impulses to the brain, central processing and efferent conduction, intervenes between sufficient peripheral stimulus and the voluntary signal in reaction to subjective experience. As stimulus temperature continues to rise along this time, an artefactually high threshold reading results: the steeper the temperature rise, the larger will be the artefact, particularly for submodalities with longer reaction time. The present study compared heat pain threshold, obtained through a method that involves reaction time participation, with heat pain thresholds obtained bypassing reaction time. It was found in 16 volunteers that: (a) Heat pain thresholds decreased as the rate of temperature rise increased when reaction time was not a factor (P less than 0.001). (b) Heat pain thresholds determined through the method involving reaction time participation were significantly higher than those obtained bypassing reaction time (P less than 0.01). Such difference increased with increasing rates of temperature rise. (c) Peripheral conduction velocity calculated from average reaction time was found to be approximately 0.6 m/sec.(ABSTRACT TRUNCATED AT 250 WORDS)
Cold stimuli of varying intensities were randomly applied to upper middle incisors of 12 healthy young subjects for a mean duration of 2 min by individually adapted thermodes the temperatures of which ranged from +30 degrees C to -30 degrees C. The subjects were asked to rate the magnitude of their pain sensations during application of the stimuli by means of a linear potentiometer according to a category scale. After each stimulus, they were asked to describe the quality of their pain sensations. Cold stimulation of the teeth evoked pain sensations were reproducible that in subsequent trials and could be graded according to stimulation intensity. Below certain individually different threshold thermode temperatures the onset of a stimulus was followed, after a short latency (1.6 +/- 1 sec), by a sharp and shooting pain sensation which immediately decreased after reaching its maximum value while the stimulus was still present. The mean maxima of the pain intensities were correlated to the thermode temperature. In general, this first pain component was followed by a second one (latency: 29.9 +/- 6.3 sec) with a lower threshold temperature, less of an increase in rate and lower magnitude. This was described as a dull, burning pain which was difficult to localize. The human pain ratings are compared to recordings of intradental nerve fibres in the cat and, under the assumption that the response behaviour of human pulpal nerve fibres is comparable to that of the cat, we hypothesize that the first pain component is evoked by intradental A delta fibres exhibiting their typical phasic response behaviour and firing during the initial steep temperature decrease. After some seconds, intradental temperature reached values sufficient to evoke C-fibre activity associated with the second pain component.
Changes in sensory irritation were measured during repeated topical exposures to capsaicin over 2 days. The perceived intensities of itching and pungent sensations, predominantly burning and stinging/pricking, were assessed every 60 sec during 5 applications of capsaicin at inter-stimulus intervals (ISI) of 90 min (Exp. 1) or 15 min (Exp. 2) and in follow-up tests 24 h later. Psychophysical measurements were obtained with a hand-held dynamometer in conjunction with the method of magnitude production. When the ISI was 90 min, itching and pungency were both significantly reduced (i.e., desensitization occurred) by the fifth exposure; however, the reduction occurred more rapidly and dramatically for itching. After 24 h, desensitization remained significant only for itching. When the ISI was 15 min, the sensations on day 1 first intensified in a manner consistent with sensitization, then declined in a manner consistent with desensitization; compared to pungency, itch exhibited less sensitization and more desensitization. On day 2, overall intensity was less for both categories of sensation, primarily because of a reduction in sensitization. Marked individual differences were observed in the overall sensitivity to capsaicin, the time course of sensation, the susceptibility to capsaicin-induced itch, and the rate and duration of sensitization and desensitization. The results are discussed in terms of current hypotheses about the sensory mechanisms that underlie chemically induced itch and the use of capsaicin as a topical analgesic and antipruritic.
OBJECTIVE: There were two objectives in this research. First, to develop and evaluate the criterion validity of a questionnaire measure of sensation seeking in children, by examining how scores on this instrument relate to various indices of physical risk taking in children 7-12 years of age. Second, to develop both a parent-report and child-report version of the instrument. METHODS: Drawing on the literature, items tapping five potential aspects of sensation seeking were developed, with parents and children responding to comparable items. For each of these five subscales, internal reliability estimates were computed separately for the parent-report and child-report versions. To establish criterion validity, subscale scores were related to three indices of children's risk taking commonly used in research: actual risk taking, intentions-to-risk take, self-reports about risk taking on a standardized questionnaire. RESULTS: On both the child-report and parent-report versions, the same three of the five subscales yielded acceptable internal reliability scores and significantly related to the various indices of risk taking. CONCLUSIONS: This new measure adequately assesses aspects of sensation seeking relevant to children's risk taking. Because individuals high in sensation seeking engage in greater risk taking and are at increased risk of injury, this instrument may prove particularly useful to aid in identifying those children most likely to engage in injury-risk behaviors so that targeted interventions can be applied to this group.
The tendency for occasional risk-taking was compared with the tendency for frequent risk-taking within a population of 201 young people. Positive affectivity, negative affectivity, sensation seeking, and risk-taking were measured for the domains of substance use, behavior on the road, sexual relations, and deviant behavior. The tendencies for occasional versus frequent risk-taking generalize across three of the four domains. Multivariate analysis show that demographics variables and personality traits do not predict the tendency for occasional risk-taking as well as they predict the tendency for frequent risk-taking. Furthermore, sensation seeking is the only trait linked to the tendency for occasional risk-taking in the domains of substance use and deviant behavior. The tendency for frequent risk-taking, notably in the domain of substance use, is predicted by age, sensation seeking, and negative affectivity. The other three domains are only predicted by sensation seeking. The results support the idea that the tendency for occasional risk-taking is distinct from the tendency for frequent risk-taking and that the two tendencies are not controlled by the same determinisms.
The personality traits of impulsivity and sensation seeking have been proposed as important features of early-onset alcoholism. Early-onset (EOA, n=62) and late-onset (LOA, n=68 ) alcoholic inpatients were compared as to the severity of their substance use and related problems, and self-report scales measuring impulsivity (Barratt Impulsiveness Scale, version 11), sensation seeking (Sensation Seeking Scale), and aggressiveness (Buss Durkee Hostility Inventory). The symptom severity of the EOAs' alcohol-use disorder and related problems was higher than that of the LOAs. Furthermore, the EOAs had higher levels of impulsivity, sensation seeking, and aggression relative to the LOAs. The differences in impulsivity remained after an analysis controlling for the effect of aggressiveness. Finally, cigarette smoking was positively correlated with impulsiveness across alcoholic subgroups. Active screening for impulsive traits in treatment-seeking alcohol-abusing populations is recommended to improve treatment planning and prevent early drop-out.
OBJECTIVE: To compare the effect of real and sham acupuncture and a control intervention on thermal sensation and thermal pain thresholds. DESIGN: Single-blind, randomized controlled, repeated-measures trial. SETTING: Laboratory. PARTICIPANTS: Eighteen acupuncture-naive, healthy subjects with no history of upper-limb pathology or acupuncture contraindications. INTERVENTION: Subjects were randomly assigned (blind card allocation) to 1 of 6 possible orders of application of the interventions, which consisted of 25 minutes each of control, real, and sham acupuncture. MAIN OUTCOME MEASURES: Thermal sensation and thermal pain thresholds measured with a thermal sensory analyzer before and after each intervention. RESULTS: There were increases in cold and hot pain and cold sensation thresholds with real acupuncture. The level of increase did not differ significantly from the changes that occurred with sham acupuncture and control interventions. CONCLUSIONS: Although we observed a trend toward a decreased sensitivity to thermal pain and thermal sensation with real acupuncture, this trend did not differ significantly from the changes with control or sham interventions. Therefore, no support was provided for analgesic or placebo effects of acupuncture. The trend, combined with the relatively low power of the inferential tests applied does, however, suggest that further research is merited.
This descriptive correlational study examined the relationships of sexual sensation seeking, self-esteem, and self-efficacy in condom use, stages of change, and alcohol consumption to HIV risk-taking behaviors among college students. A total of 159 students completed an online survey in 2004. Instruments included the Sexual Sensation Seeking Scale, College Alcohol Problems Scale, Condom Use Scale, and Rosenberg Self-Esteem Scale. High sensation seekers had higher self-esteem, more self-efficacy in condom usage, fewer problems associated with alcohol consumption, and belonged to Greek organizations (F [1,158] = 12.54; p < .0005). Women who were high sensation seekers perceived more advantages (F [1, 116] = 1.67; p = .05) than disadvantages (F [1, 116] = 2.01; p = .01) to using condoms. Men consumed significantly more alcohol and had more social problems related to alcohol use than women (F [1, 158] = 5.04; p < .03). Students in Greek organizations had significantly more positive attitudes (X(2) [1] = 4.55; p < .03) and more respect for themselves (X(2) [1] = 11.22; p < .0008) than other students and were more likely to be tested for HIV (X(2) [1] = 3.85; p < .05). Students with low self-esteem consumed more alcohol, had more sexual partners, and had more HIV risk-taking behaviors than other students. Even though students were reported to be efficacious in condom usage, they used them inconsistently with their sexual partners and were in the earlier stages of change. Interventions are needed in the community to help sexually active individuals take responsibility for their sexual health and to increase the awareness of the need to be tested for HIV.
OBJECTIVE: The objective of this study was to obtain data on the incidence and relationship of psychological factors to tattooing and body piercing from a large and representative sample of German citizens (N=2043). METHODOLOGY: Representative data (sample age range=14-93 years) were evaluated with respect to health-related quality of life (SF-36), mental health (General Health Questionnaire), mental disorders (Patient Health Questionnaire), and sensation seeking (Arnett Inventory of Sensation Seeking). RESULTS: The prevalence of tattooing and that of body piercing in the general German population are 8.5% and 6.5%, respectively. Individuals aged between 14 and 24 years display the highest rate of body piercings or tattoos (females, 41%; males, 27%). Within the group of individuals aged between 14 and 44 years, unemployment and nonaffiliation to a church are positively correlated, tattooing is significantly correlated with the perception of reduced mental health, and both tattooing and body piercing are correlated with significantly increased sensation-seeking behavior. CONCLUSIONS: Next to being motivated by fashion and the urge to fit in with one's peers, the major reasons for body modification practices in the German population appear to be negatively perceived conditions of life, reduced social integration, and increased sensation-seeking behavior.
Recent studies demonstrated tactile illusions in healthy subjects by manipulating visual and tactile information. For example, a rubber hand, lying on a table in front of the subject and not connected with the body, can be felt by the subject as belonging to his or her own body by a simple visuotactile manipulation. Aim of the present study was to create an illusion in which the subject feels touch on a body site which is different from the actual touch, hence showing a referral of touch similar to those reported in phantom limb patients. Since it is known from animal studies that tactile illusions can alter early sensory processing, we were interested in the role of the primary somatosensory cortex (SI) during this kind of illusion. Thus, we manipulated the visual and tactile information in eight healthy subjects. The participants were stimulated on their fifth digit (D5) while watching a video, which showed a life-sized hand where the first digit (D1) was stimulated, hence inducing a conflict in feeling and seeing. The visual and tactile stimulation was in-phase in one condition and out-of-phase in a control condition. The video was presented in the peripersonal space of the subject at the distance where the real hand would be expected. Subjects reported a referred sensation of feeling the stimulation on D1 instead of D5 when the stimulation was in-phase with the video. Neuromagnetic source imaging of the topography of the functional organization of SI related to tactile stimulation of D1 and D5 showed that the source extent of the cortical representation of D5 increased during the illusion. The results suggest that a simple manipulation of visual and tactile information can induce referred sensations in healthy subjects in a very fast manner. Since the amount of the referred sensation was significantly correlated with the modulation in SI, we argue that SI is involved in this kind of artificially induced referred sensation.
We studied the effect of abolishing cutaneous sensation (by infiltrating local anaesthetic around the median nerve at the wrist) on the ability of 10 healthy volunteers (a) to maintain a submaximal isometric pinch-grip force for 30 s without visual feedback, and (b) to perform a fine finger-manipulation 'handwriting' task. Blocking cutaneous sensation had no effect on ability to maintain pinch force, suggesting that muscle afferents have the major role in force-control feedback. However, a near-linear fall in force, present with or without block (mean slope=-1.3+/-0.2% s(-1)), which cannot be attributed to motor fatigue, reveals a shortcoming of the afferent feedback system. Blocking cutaneous sensation did impair ability to perform the more demanding writing task, as judged by an 18+/-6% increase in the length of the path between target points, a 22+/-9% increase in the duration of the movement and a 63+/-24% in 'normalised averaged rectified jerk', an averaged time-derivative of acceleration (all significantly nonzero, P < 0.04). These experiments demonstrate the relative importance of muscular and cutaneous afferent feedback on two aspects of hand performance, and provide a way to quantify the deficit resulting from the lack of cutaneous sensation.
A paradoxical painful sensation can be elicited by the simultaneous application of innocuous warm and cold stimuli to the skin. In the present study, we analyzed the conditions of production of this unique experimental illusion of pain in 52 healthy volunteers (27 men, 25 women). The stimuli were produced by a thermode composed of six bars whose temperature was controlled by Peltier elements. The temperature of alternate (even- and odd-numbered) bars could be controlled independently to produce various patterns of the 'thermal grill'. After measuring the cold and heat pain thresholds, a series of combinations of warm and cold stimuli, whose distance to the thermal pain threshold was at least 4 degrees C, were applied on the palmar surface of the right hand during 30s. After each stimulus, the subjects had to describe and rate their sensations on visual analog scales. Paradoxical painful sensations, mostly described as burning, were reported by all the subjects but three. However, the phenomenon was less frequent in approximately one third of ('low responder') volunteers. The frequency and intensity of such painful sensations were directly related to the magnitude (i.e. 5-25 degrees C) of the difference of the temperature between the warm and cold bars of the grill. The combination of increasingly colder temperature to a given warm temperature induces similar effects as combining increasingly warmer temperature to a given cold temperature. These results suggest that pain can be the result of a simple addition of non-noxious warm and cold signals.
OBJECTIVES: To investigate the feasibility, safety, and efficacy of perineal cutaneous application of capsaicin as a test for the diagnosis, as well as a potential therapeutic tool, in patients with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). METHODS: We recruited 22 patients (mean age 34.5 years, range 19 to 56), who had been diagnosed with CP/CPPS according to the National Institutes of Health criteria, and 6 healthy control subjects. Both groups received a topical application of 5 mL capsaicin at a concentration of 10(-5) M to the perineal body skin. The patients were asked to mark on a visual analogue scale the intensity of any heat or burning sensation. All the patients had completed a National Institutes of Health Chronic Prostatitis Symptom Index before and 1 week after the test. The scores of the two groups were compared using the Mann-Whitney U test. RESULTS: The patients with CP/CPPS reported a heat/burning sensation intensity that was statistically greater than that of the healthy controls (7.5 versus 4.3, P <0.001) and a shorter time to heat sensation onset and maximal intensity (1.5 versus 3.4 minutes, P <0.001, and 2.5 versus 7 minutes, P <0.001, respectively). Of the 22 patients, 16 reported an improvement of symptoms after 7 days and the mean National Institutes of Health Chronic Prostatitis Symptom Index score decreased from 27 to 16 (P <0.01). CONCLUSIONS: We found a statistically significant difference in the pain visual analogue scale and interval between topical application and the onset of the heat/burning sensation between patients with CP/CPPS and healthy controls. The small sample size strongly suggests the need for additional larger and more controlled studies.
It has been argued that panic disorder patients may be more skilled at detecting changes in actual physiology than others. The present study investigated if panic patients are better than controls in perceiving sensations produced by light hyperventilation. Twelve panic patients and 28 control subjects underwent a procedure in which they were exposed 12 times to 1 min of light hyperventilation or 1 min of 'placebo' hyperventilation (isocapnia). Differences in sensations reported during real hyperventilation were compared to sensations reported during 'placebo' hyperventilation. Results demonstrated an absence of superior perception of hyperventilatory sensations in panic patients.