Prism adaptation contrasts perceptual habituation for repetitive somatosensory stimuli.

Prism adaptation (PA) is a non-invasive procedure that requires performing a visuo-motor pointing task while wearing prism goggles inducing a visual displacement of the pointed target. This procedure involves a reorganization of sensorimotor coordination, and induces long-lasting effects on numerous higher-order cognitive functions in healthy volunteers and neglect patients. Prismatic displacement (PD) of the visual field can be induced when prisms are worn but no sensorimotor task is required. In this case, it is unlikely that any subsequent reorganization takes place. The effects of PD are short-lived in the sense that they last as long as prisms are worn. In this study we aimed, to the best of our knowledge for the first time, at investigating whether PA and PD induce changes in the perception of intensity of nociceptive and non- nociceptive somatosensory stimuli. We induced, in healthy volunteers, PD (experiment 1), or PA (experiment 2) and asked participants to rate the intensity of the stimuli applied to the hand undergoing the visuo-proprioceptive conflict (experiment 1) or adaptation (experiment 2). Our results indicate that: 1) the visuo-proprioceptive conflict induced by PD does not reduce the perceived intensity of the stimuli, 2) PA prevents perceptual habituation for both nociceptive and non-nociceptive somatosensory stimuli. Moreover, to investigate the possible underlying mechanisms of the effects of PA we conducted a third experiment in which stimuli were applied both at the adapted and the non-adapted hand. In line with the results of experiment 2, we found that perceptual habituation was prevented for stimuli applied onto the adapted hand. Moreover, we observed the same finding for stimuli applied onto the non-adapted hand. This result suggests that the detention of habituation is not merely driven by changes in spatial attention allocation. Taken together, these data indicate that prisms can affect the perceived intensity of somatosensory stimuli, but only when PA is induced.

Avances en el tratamiento del púrpura trombocitopénico inmunológico refractario / Advances in inmune refractary thrombocytopenic purpura treatment

Se analiza las posibilidades terapéuticas, actualmente aceptadas o en estudio, en los pacientes portadores de PTI refractario (definido como aquél que no ha respondido a esplenectomía y esteroides suprarrenales). Considerando que la trombocitopenia depende de la producción de anticuerpos antiplaquetarios, su unión a los trombocitos y la destrucción de éstos por los macrófagos del sistema retículoendotelial, se analiza el uso de fármacos que rompen esta cadena de eventos y pueden provocar mejoría del cuadro clínico. Entre éstos, se discute la utilidad de inmunosupresores (ciclofosfamida - azatioprina - vincristina - vinblastina y colchicina) administrados por distintas vías y con diversos fundamentos fisiopatológicos; se revisa experiencia en el uso de gamaglobulinas intravenosas; se menciona el uso del anabólico Danazol y sus posibilidades. Brevemente, se toca el uso de plasmaféresis y transfusión de plaquetas, como terapias de apoyo y se pretende dar una visión global que permite escoger un método de trabajo en el tratamiento de estos enfermos