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    Does the processing of hypnotic analgesia require attention-demanding resources? : a dual task analysis of hypnotic-susceptibility-mediated differences in executive attentional processing between hypnotic and nonhypnotic analgesia : a thesis presented in part fulfilment of the requirements for the degree of Master of Arts in Psychology at Massey University
    (Massey University, 2000) Smeets, Louis
    There is substantial evidence that hypnotic analgesia can be effective in reducing pain and distress in both experimental and clinical settings in at least a sizeable portion of the population. However, the mechanism whereby hypnosis achieves this are not well-understood and various explanations have been proposed. These offer fundamentally different predictions about the attentional involvement of hypnotic analgesia, which are highly relevant to pain research as the disruption of ongoing activity is one of the more debilitating aspects of pain. While cognitive-behavioural coping strategies may attenuate pain of short duration, their effortful deployment further interferes with ongoing activity, and there are strong indications that their effectiveness rather rapidly decreases as pain perseveres. If as dissociated-control theory proposes, hypnotic analgesia does not require attentional effort for its execution, it would provide significant advantages for individuals who can effectively achieve it (i.e., those who are highly susceptible to hypnotic suggestions). This hypothesis was further tested in an experimental study using a dual-task scenario and repeated-measures design. One hundred and ninety student volunteers were first screened for hypnotic susceptibility using the Hardvard Group Scale of Hypnotic Susceptibility: Form A, and seventy-eight also completed a more demanding follow-up assessment using the Waterloo-Stanford Group C scale. This resulted in fifty individuals who qualified for participation in the experimental part of the study by scoring as either high or low hypnotisable on both these measures. Of these, 12 lows and 14 highs went on to take part in an experimental study that had high and low hypnotisables performed a cognitively demanding tracking task while using either hypnotic analgesia or cognitive-behavioural strategies to cope with iontophoretically administered pain. Interruption of tracking performance during each coping method was used as a measure of central attentional resources needed to execute that coping strategy. Results did not find evidence for the hypothesised absence of interference effects among high hypnotisables using hypnotic analgesia. Possible reasons are examined and exploration of data indicates that the tracking task was not difficult enough to require significant and continuous attention, and lacked sensitivity to distinguish interference effects between treatment conditions. Findings do not allow a conclusion of support for either explanation of the mechanisms underlying effective hypnotic analgesia. Highly hypnotisable subjects using hypnotic analgesia did achieve significantly greater reductions in both the intensity and unpleasantness of the pain than low hypnotisables using hypnotic analgesia or high and low hypnotisables using cognitive-behavioural coping strategies. Characteristics of the attentional capture of visual motion are discussed and suggestions made for future research and improvements to the design of the current study. Considerable attention is given to findings of a large body of neurophysiological studies of brain activity and a proposed neuropsychophysiological model of hypnosis. When combined, results of these studies indicate that: the mechanisms of attentional control involved in the process of hypnosis are fundamentally different from those involved in the use of standard cognitive-behavioural strategies, but that both processes do require central attentional effort and resources.
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    Paced serial addition : an investigation into the nature of the cognitive processes involved in PASAT performance : thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Psychology at Massey University
    (Massey University, 1995) Stewart, Mark
    The Paced Auditory Serial Addition Test (PASAT) of Gronwall and Sampson (1974) is a neuropsychological test of attention used in both research and clinical settings (Lezak,1983). However, a review of the literature revealed that the cognitive processes and attentional factors underlying PASAT performance are not well understood. Two experiments were conducted with the aim of providing further empirical and theoretical insights into PASAT performance. In Experiment 1, 16 subjects (8 male and 8 female) performed auditory and visual versions of a shortened paced serial addition task. It was found that PASAT performance in the visual stimulus modality was superior, but that, as indexed by accuracy and error scores, the pattern of performance as a function of the rate of stimulus presentation (1.2, 1.6, 2.0, and 2.4 s) was similar. These results are consistent with the idea that the nature of the cognitive processing involved is independent of stimulus modality. The design of Experiment 2 was the same as the first, except that divided field stimulus presentation was used in an attempt to test two opposing theories of attention. The results were not consistent with the hypothesis. The findings of both experiments were discussed in terms of the possible role of attention deficits in PASAT performance. An interesting finding was that the superior performance of male subjects in Experiment 1 was reversed in Experiment 2. This differential effect for divided field stimulus presentation as a function of gender may be partly accounted for by differing degrees of cerebral lateralisation for males and females.
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    Traumatic brain injury and substance use in a prison population : lifetime prevalence rates and neuropsychological sequelae : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Psychology at Massey University
    (Massey University, 1995) Barnfield, Tracey V
    The present study investigated the rates of traumatic brain injury (TBI) and substance use in a prison population, and the effect of these on neuropsychological functioning. The study was conducted in two parts. In the first part, responses to a screening questionnaire indicated that 86.4% of the 118 subjects had sustained TBI, 56.7% reported more than one TBI, and Maori subjects sustained 12 % more TBI than non-Maori. Subjects reported higher rates of illicit substance use than the general population, and Maori reported higher substance use than non-Maori. All subjects reported difficulties with general memory and socialisation on a Problem Rating Scale, but no differences were found in the level of difficulties reported due to severity of TBI sustained. Subjects with more severe substance use histories reported experiencing most problems with interpersonal relationships, family, and finances. In part two, 50 subjects from the original sample with a history of TBI and/or substance use, completed neuropsychological measures of short and long term verbal and visual memory, learning, information processing, motor speed and co-ordination, executive functioning, and malingering. All subjects performed below norms on tests of verbal memory and verbal abstract thinking, but overall, no differences were found due to either severity of TBI or level of substance use. Maori subjects obtained the lowest scores on tests of verbal ability, but also reported higher rates of TBI and substance use, which is presumed to account for this result. In conclusion, prison populations seem to have a disproportionably high TBI rate, recurrent TBI rate, and substance use rate, compared to the general population. Further, there are a group of individuals who have experienced both TBI and substance abuse, and consequently have impairments in verbal memory and learning, abstract thinking, and report problems with general memory and socialisation. These difficulties should be taken into account, since they may affect functioning both in prison and following release.
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    Potassium iontophoresis as an experimental pain stimulus : its psychophysical characteristics and its utility for investigating the spinal modulation of pain : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University
    (Massey University, 1995) Humphries, Steven Albert
    The present study investigated the psychophysical characteristics of potassium iontophoresis and its suitability as an experimental pain stimulus. Experiment One 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. Experiment Two determined the optimal inter-stimulus interval (ISI) for reliable pain reporting and evaluated stimulus history effects, both in terms of session effects and the effects of immediately preceding stimuli. Experiment Three compared potassium iontophoresis 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 seconds. 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 sodium iontophoresis. It was concluded that potassium iontophoresis is a convenient and reliable experimental pain stimulus. It can be presented rapidly and repeatedly with minimal loss in consistency of subject pain report. Potassium iontophoresis provides a technique for investigating the neural modulation of pain in the relative absence of inflammation processes and tissue damage. The properties of potassium iontophoresis determined in Experiments One, Two and Three indicated that it could be an ideal nociceptive stimulus for a quantitative analysis of some of the spinal modulation mechanisms predicted by the gate control theory of pain. Clinical and experimental support for the gate control theory of pain was overviewed. According to the gate control theory of pain a peripheral stimulus that activated both small and large-diameter afferent fibres would be perceived as painful, though there would be some reduction in the intensity of the pain due to the inhibitory action of the large fibre activity. The present study investigated a prediction of gate control theory that there would be a transient increase in pain above that of the background level - a pulse of pain - as the pain stimulus was being ramped off due to the large fibre activity at the spinal level falling away more quickly due to the different peripheral conduction velocities of large and small fibres. A further prediction was that the more distant the peripheral stimulus was from the spine the greater the pain pulse would be for any given ramp-off rate. Supraspinal pain modulatory mechanisms were overviewed but excluded as possibly obscuring the predicted pain pulse generated through the ramping off of the peripheral nociceptive stimulus. Fourteen subjects had the experimental pain stimulus of iontophoretically applied potassium ions (K+) applied to an upper and a lower site on the dominant arm. Each stimulus trial consisted of four seconds of constant pain followed by the stimulus being ramped off. In a threshold detection task a double random staircase method was used to adjust the ramp-off rate. Subjects were asked to indicate if they could detect a brief pulse of additional pain during this ramp-off phase. Subjects were clearly able to detect a pulse of pain at both sites. The average rate of stimulus ramp-off in order to detect a pain pulse was statistically greater for the upper-arm site (14.3 µg K+/s), than for the lower-arm site (9.4 µg K+/s). The average ramp-off time required to generate a detectable pain pulse was 192 ms and 261 ms for the upper and lower arm sites respectively. These results were consistent with the predictions of gate control theory and our ramp-off model. Alternative explanations for the results, including intrinsic differences in nociceptive responding for different dermatomes and anode break excitation, 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 as described by the gate control theory of pain. However, further studies would be required to confirm the causal mechanisms that generate the observed pulse of pain.
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    The quicksilver quest : two psychological studies investigating the effects of mercury in dentistry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University, Wellington Campus, New Zealand
    (Massey University, 2005) Jones, Linda Miriam
    The longstanding debate over the safety of mercury in dentistry has latterly moved from scientific argument to public health dilemma. Mercury is a neurotoxin. Adverse psychological outcomes can result from exposure, so The Quicksilver Quest aimed to investigate mercury in dentistry from a qualitative, critical health psychology perspective, and a quantitative, neuropsychology assessment. The qualitative study used focus group methodology to explore micro-mercurialism linked to dental amalgam fillings. A random sample of people, who had been medically diagnosed with mercury poisoning, formed seven focus groups. The discussion of experiences, beliefs, and health was analysed for themes and issues. The main findings were that the participants were not a homogeneous group, as had been anticipated, but fell into categories differentiated by their symptoms, fiscal resources, and motivation. A placebo effect was rejected as an exclusive explanation for the positive health outcomes reported by those who had had amalgam removal and detoxification. The quantitative study investigated the long-term effects of occupational mercury exposure on a cohort of women in dentistry. The aim was to test the null hypothesis: that women who endured high occupational mercury exposure in the 1970s (43 participants), and matched controls (32 participants), would show no between-group differences on a general and reproductive health survey, and a nine-test neurobehavioural assessment. Results generally supported accepting the null hypothesis. Significant exceptions were current symptom experience, reproductive health, and two mood subscales. There was a suggestion of peripheral nerve damage in the exposed group. Overall, the general discussion systematically reviews tension points in the debate, in light of a proposed model of tolerance to mercury. This begins to explain how it might appear that mercury in dentistry is safe for dental personnel, as pro-amalgam debaters claim, yet unsafe for some dental patients, as anti-amalgam debaters claim. Further study is suggested for occupationally exposed women, on tremor, and to test the proposed tolerance to mercury model. Finally, as the debate has a political aspect, a recommendation is made for a shift in public health policy to dental amalgam being restricted to use only in an adult population.