An investigation of the gate control theory of pain using the experimental pain stimulus of potassium iontophoresis.

This study investigated a prediction derived from gate control theory-that there would be a pulse of pain as a pain stimulus was being ramped off due to the rapidly transmitting, inhibitory large fiber activity falling away sooner at the spinal level than the excitatory activity of the slow-transmitting, small nociceptive afferents. A further prediction was that the more distant the peripheral stimulus was from the spine, the greater the pain pulse would be. Fourteen subjects had the pain stimulus of iontophoretically applied potassium ions (K+) applied to an upper and a lower site on the dominant arm. In a threshold detection task using the double random staircase method, subjects were asked to indicate whether they could detect a pulse of additional pain during this ramp-off phase. The average rate of stimulus ramp-off in order to detect a pain pulse was statistically greater for the upper-arm site (14.3 micrograms K+/sec) than for the lower-arm site (9.4 micrograms K+/sec). These results were consistent with gate control theory. Alternative explanations, including intrinsic differences in nociceptive responding for different dermatomes and anode break, were considered. It was concluded that the detection of a pain pulse during the ramping off of a peripheral pain stimulus potentially provides a quantitative measure of the spinal modulation of pain.

Causal attributions for criminal offending and sexual arousal: comparison of child sex offenders with other offenders.

Causal attributions for their offending, and for sexual arousal and sexual behaviour, were investigated for 50 males convicted of child sex offences. These attributions were compared with those obtained from 150 males convicted of one of three other criminal offences: rape, property offences and violent offences against persons. In semi-structured interviews, the Offence and Sexual Arousal and Behaviour Attribution Questionnaires were administered. Offenders offered causal attributions for their offending and for their sexual arousal, and they rated these causes on attribution dimensions. Results showed that child sex offenders attributed both their offending and their sexual arousal to internal, stable and uncontrollable causes. Rapists and property offenders attributed their offending behaviour to external, stable and uncontrollable causes; and violent offenders to internal, stable and uncontrollable causes. In contrast to child sex offenders, the other three groups all attributed their sexual arousal and sexual behaviour to external, unstable and controllable causes. The findings are discussed in terms of their implications for intervention programmes.

Iontophoretically applied potassium ions as an experimental pain stimulus for investigating pain mechanisms.

The present study investigated the psychophysical characteristics of potassium iontophoresis and its suitability as an experimental pain stimulus. Experiment 1 investigated the optimal duration of the pain stimulus for reliable reporting across repeated trials and whether the relationship between stimulus and subject response was linear, logarithmic, or a power function. In Experiment 2, the optimal interstimulus interval (ISI) was determined for reliable pain reporting, and stimulus history effects, both in terms of session effects and the effects of immediately preceding stimuli, were evaluated. In Experiment 3, potassium iontophoresis was compared with a sodium iontophoresis control. Linear functions described the stimulus-pain relationship best. No significant differences in the goodness-of-fit coefficients of determination, correlations, or coefficients of variation were found for the stimulus durations of 1, 2, and 4 sec. Significant stimulus history effects were found across a session, with adaptation and enhancement of responding for low- and moderate-intensity stimuli, respectively. The effects of the immediately preceding stimuli were suppression or enhancement of pain response, depending on the ISI, the preceding stimulus intensity, and the present stimulus intensity. Potassium iontophoresis was a significantly more effective pain stimulus than was sodium iontophoresis. It was concluded that potassium iontophoresis is a convenient and reliable experimental pain stimulus, which can be presented rapidly and repeatedly with minimal loss in consistency of subject pain report. Potassium iontophoresis provides a tool for investigating the neural modulation of pain in the relative absence of inflammation processes and tissue damage.

Transfer of learning in transformed random-dot stereostimuli.

The transfer of learning between normal and monocularly-transformed small-disparity, random-dot stereostimuli has been examined under extended viewing conditions. When the disparity value was constant, transfer of learning between normal and monocularly-transformed stereostimuli was disrupted by both low-frequency and high-frequency transformations. These results suggest that stereolearning is restricted to disparity units that are selective to the same spatial-frequency characteristics.