Everyone has felt those tingling, tickly sensations occurring spontaneously all over the body in the absence of stimuli. But does anyone know where they come from? Here, right-handed subjects were asked to focus on one hand while looking at it and while looking away and subsequently to map and describe the spatial and qualitative attributes of sensations arising spontaneously. The spatial distribution of spontaneous sensations followed a proximo-distal gradient, similar to the one previously described for the density of receptive units. (...) The intensity and spatial extent of the reported sensations were modulated by the focusing condition, especially in respect of the left hand. Convergent focusing acted upon the conscious perception of sensations by enhancing or suppressing them. To our knowledge, this is the first ever study of spontaneous sensations, and it offers considerable insight into their sources. The presence of the proximo-distal distributional gradient is a clear sign that receptive units are involved. The enhancement/suppression effects also confirm the involvement of attention. Finally, left-hand dominance suggests several right-hemisphere processes may be involved, such as spatial and tactile perception, and probably interoception. (shrink)

Subtle bodily sensations such as itching or fluttering that occur in the absence of any external trigger may serve to locate the spatial boundaries of the body. They may constitute the normal counterpart of extreme conditions in which body-related hallucinations and perceptual aberrations are experienced. Previous investigations have suggested that situations in which the body is spontaneously experienced as being deformed are related to the ability to perform own-body transformations, i.e., mental rotations of the body requiring disembodiment. We therefore decided (...) to consider whether the perception of SPS might relate to embodiment as assessed through the ability to perform own-body transformations and schizotypal traits, since high degrees of schizotypy in the general population have been associated with more vivid perceptions and aberrant perceptual experiences. Then participants completed a standard SPS task. Our analysis revealed that the slower the response time in the OBT task, the more frequent the perception of SPS. This suggests that difficulties in disembodying and mentally transforming one’s own body facilitate feeling oneself. Furthermore, a greater number of correct responses in the OBT task was associated with less frequent perception of SPS. This suggests that finding it easier to disembody and perform mental own-body transformations interferes with the ability to sense oneself. The results also show that higher schizotypal traits, as assessed through the SPQ, are associated with more frequent perception of SPS. Taken together, these results provide a coherent picture and suggest that embodiment is required in order to correctly feel oneself, as expressed through the perception of SPS. The ability to easily experience disembodiment reduces the sense of feeling oneself, and proneness to schizotypal traits produces body misperceptions that enhance and amplify this feeling. The results are discussed in the light of current knowledge and theories about body representations, taking into account attention and interoception as factors that influence body awareness. We offer explanations for perceptual aberrations, body-related delusions, and hallucinations based on misperceived or misinterpreted SPS, and we discuss possible mechanisms that may contribute to feeling and misperceiving oneself. (shrink)