Lines of research

In a first line of research, we investigate the effects of changing the shape of the body on sensory and motor systems both in human subjects and in animals. By displacing fingers, lips and ears in humans, we found that both a perceptual and a motor reorganization occur. In particular, after a period of distorted tactile perception and erroneous motor behavior, subjects learn to perceive correctly tactile stimuli applied to the artificially displaced body parts: analogously, a motor learning occurs. We reproduced the same experiments in mice whose vibrissae and ears were displaced in unusual positions. For example, the superior vibrissae were bent into the inferior portion of the visual field. In normal mice, tactile and visual receptive fields of the superior colliculus multisensory neurons are aligned such that sensory inputs coming from the same portion of space converge onto the same neurons. In experimental mice, we found a modification of this alignment: for example, the superior vibrissae, normally aligned with the superior portion of the visual field, resulted to be aligned with the inferior portion when bent downward. These results demonstrate that the multisensory neurons of the superior colliculus are experience-dependent and suggest that the superior colliculus processes sensory information according to synchronous sensory activity coming from the same point of space. In a second line of research, we study the role of opioid neuropeptides and cholecystokinin (CCK) in the placebo response. Placebo analgesia is mediated by endogenous opiates, as demonstrated by its reversal by means of the opiate antagonist naloxone. We showed that, by blocking CCK by means of the antagonist proglumide, placebo analgesia results to be potentiated. This demonstrates that CCK plays an inhibitory role in placebo response, probably through an inhibitory control on opioid neuropeptides. In addition, we investigate the role of CCK in nocebo response by means of its antagonist proglumide and CCK-B specific antagonist L-365,260. In this case, the nocebo effect seems to be mediated by the CCK-B receptors; in fact, their blockade abolishes the increase of pain. These results, taken together, show that the placebo response can be modulated in two opposite directions by two different classes of endogenous neuropeptides: opiates and CCK.