Neurología : publicación oficial de la Sociedad Española de Neurología
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All pharmacological treatment is surrounded by a psychosocial context that contributes in part to the outcome of the therapy. The placebo effect is the improvement observed after a simulated treatment in which the subject, without his or her knowledge, is exposed only to the psychosocial context surrounding the treatment, without receiving the pure "pharmacodynamic" effect of the medication. The aim of this paper is to examine which brain regions and neurochemical mechanisms are responsible for the analgesia resulting from the placebo. ⋯ In placebo analgesia at least two anatomically differentiated cerebral systems work together. The guiding mechanism, which appears to be located prefrontally, is activated first. This system would influence other cortical regions (cingulate and insula), attenuating the processing of nociceptive information at these higher levels.