The effect of perceptual training on somatosensory distortion in physical symptom reporters

ABSTRACTA thesis submitted to the University of Manchester for the degree of Doctor of Clinical PsychologyLaura Rowlands30th June 2011 Thesis Title: The effect of perceptual training on somatosensory distortions in physical symptom reporters.Objective: The perceptual mechanisms underlying the development and maintenance of excessive physical symptom reporting (i.e. ? somatisation? ) are poorly understood. Research with non-clinical participants suggests that high and low symptom reporters perform differently when detecting somatosensory signals and have different false alarm rates in which the presence of a signal is incorrectly reported when no signal is present. High symptom reporters often incorrectly report the presence of a signal particularly when a stimulus in a different sensory modality is presented. Previous research has shown that it may be possible to reduce false alarm rates by perceptual training using bi-modal visuo-tactile stimuli pairing. The current was designed to test this hypothesis. Methods: Seventy non-clinical participants scoring either high or low on the Patient Health Questionnaire (PHQ-15; a measure of somatisation) completed the Somatic Signal Detection Task (SSDT), a novel perceptual paradigm that purports to measure individual differences in somatosensory distortion. Prior to the SSDT, approximately two thirds of the sample completed either a ? weak? or ? strong? perceptual training protocol in which a suprathreshold tactile and visual stimuli were paired either infrequently (25%) or frequently (75%), with the intention of training participants to discriminate tactile signal from noise more effectively. The remaining participants received no perceptual training. Factors known to be strongly associated with somatisation were controlled for. Negative affectivity was controlled for using the State-Trait Anxiety Inventory Trait Version (STAI-T; Spielberger, Gorsuch & Lushene, 1970), somatosensory amplification was controlled for using the Somatosensory Amplification Scale (SSAS; Barsky, Goodson, Lane & Cleary, 1988), the Patient Health Questionnaire (PHQ-9; Kroenke, Spitzer, & Williams, 2001) was used to control for depression and the Health Anxiety Inventory-Short Version (SHAI; Salkovskis, Rimes, Warwick & Clark, 2002) was used to control for hypochondriacal factors with the Patient Health Questionnaire-Generalised Anxiety Disorder (PHQ-GAD-7; Spitzer, Kroenke, Williams & L�we, 2006) being used to control for anxiety.Results: The high PHQ-15 group reported significantly more false alarms and had a significantly higher response criterion than the low PHQ-15 group in the no perceptual training conditions. The perceptual training reduced the false alarm rate for the high PHQ-15 group but did not alter response criterion. Although the findings were in the predicted direction, neither of these findings reached significance. The effect size indicated that this was due to low power. Conclusions: The findings were suggestive of the effect of perceptual training reducing false alarm rates; however, low power meant that it was impossible to draw firm conclusions. Further research with a larger sample is required.