Location of Nociceptive Stimulus in the Peripersonal Space Impacts Pain Experience

Peripersonal space (PPS) is the area surrounding the body where we can reach, see, and interact with objects, acting as a dynamic interface between us and the environment. We expected that pain stimuli closer to the body center in the PPS would result in higher pain intensity, increment in heart rate (HR), and skin-conductance response (SCR). It was also assumed that proprioceptive systematic error toward the body center, and psychological factors such as negative affect, pain catastrophizing, and somatosensory amplification would show a positive association with pain. Sixty individuals participated in this preregistered experiment (age: 22.9 ± 6.2 years, 76% female). Thermal pain stimulation was applied on the forearm at different stimulation sites and at different elbow joint positions. Joint Position Reproduction test in the elbow joint was used to assess proprioceptive systematic error. Psychological constructs were measured with questionnaires. Based on linear mixed models, elbow position, and stimulation site showed significant main effects and interaction when the outcome was pain intensity. By adding psychological factors to the models as covariates, pain catastrophizing showed a positive association, while state negative affect showed a negative association with perceived pain. Trait negative affect, somatosensory amplification, and proprioceptive accuracy did not influence pain reports. Beyond the traditionally included tactile, visual, and auditory modalities, proprioception should be considered in a more complex conceptualization of PPS. Our results indicate that the location of thermal stimulation might influence pain intensity within the PPS, and that a complex interplay exists between proprioceptive information and stimulation site.