title: Selectivity of conditioned fear of touch is modulated by somatosensory precision.
abstract: Learning to initiate defenses in response to specific signals of danger is adaptive. Some chronic pain conditions, however, are characterized by widespread anxiety, avoidance, and pain consistent with a loss of defensive response specificity. Response specificity depends on ability to discriminate between safe and threatening stimuli; therefore, specificity might depend on sensory precision. This would help explain the high prevalence of chronic pain in body areas of low tactile acuity, such as the lower back, and clarify why improving sensory precision may reduce chronic pain. We compared the acquisition and generalization of fear of pain-associated vibrotactile stimuli delivered to either the hand (high tactile acuity) or the back (low tactile acuity). During acquisition, tactile stimulation at one location (CS+) predicted the noxious electrocutaneous stimulation (US), while tactile stimulation at another location (CS-) did not. Responses to three stimuli with decreasing spatial proximity to the CS+ (generalizing stimuli; GS1-3) were tested. Differential learning and generalization were compared between groups. The main outcome of fear-potentiated startle responses showed differential learning only in the hand group. Self-reported fear and expectancy confirmed differential learning and limited generalization in the hand group, and suggested undifferentiated fear and expectancy in the back group. Differences in generalization could not be inferred from the startle data. Specificity of fear responses appears to be affected by somatosensory precision. This has implications for our understanding of the role of sensory imprecision in the development of chronic pain.
authors.affiliation: Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.|Recover Injury Research Centre, Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Harvie
authors.affiliation: Research Group on Health Psychology, University of Leuven, Leuven, Belgium.|Center for Excellence on Generalization Research in Health and Psychopathology, University of Leuven, Leuven, Belgium.
authors.forename: Ann
authors.initials: A
authors.lastname: Meulders
authors.affiliation: Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors.forename: Emily
authors.initials: E
authors.lastname: Reid
authors.affiliation: Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.
authors.forename: Danny
authors.initials: D
authors.lastname: Camfferman
authors.affiliation: School of Engineering, University of South Australia, Adelaide, Australia.
authors.forename: Russell S A
authors.initials: RS
authors.lastname: Brinkworth
authors.affiliation: Sansom Institute for Health Research, University of South Australia, Adelaide, Australia.|Neuroscience Research Australia, Sydney, Australia.
authors.forename: G Lorimer
authors.initials: GL
authors.lastname: Moseley
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological / Q000502:physiology; D003214:Conditioning, Classical; D004597:Electroshock; D005239:Fear / Q000502:physiology*; D005260:Female; D005793:Generalization, Psychological / Q000502:physiology; D006801:Humans; D008297:Male; D058748:Pain Perception / Q000502:physiology*; D010812:Physical Stimulation; D013216:Reflex, Startle; D014110:Touch; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult
keywords: Classical condition; Differential conditioning; Fear conditioning; Fear of touch; Generalization; Overgeneralization; Pain