Pathological limb pain patients show decreased attention to some stimuli on the painful limb and increased attention to others, a paradox that has dogged the field for over a decade. We hypothesized that pathological pain involves a spatial inattention confined to bodily representations. Patients showed inattention to the painful side for visual processing of body parts but not letters, tactile processing but not auditory, and body-part bisection tasks but not line bisection tasks. We propose the new term "somatospatial inattention" to describe bodily-specific spatial inattention associated with pathological limb pain.

Unilateral CRPS is associated with a spatially-defined disruption of motor performance. Participants perform worse when the task is performed on the affected side of the body midline, regardless of whether they use their affected or healthy hand.

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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.

Expecting a painful stimulus in non-adjacent skin sites has spatially specific effects on pain modulation, but this reflects an interaction between the expected location of stimulation and the actual location. This suggests a more complex connection between somatotopic maps and nociceptive modulation than previously thought; several distinct mechanisms likely contribute.