Implications for psychedelic-assisted psychotherapy: a functional magnetic resonance imaging study with psilocybin

pharmacologically related to the prototypical psychedelic, lysergic acid diethylamide. Psychedelic drugs were used extensively in psychotherapy in the 1950s to lower psychological defences and facilitate emotional insight. In cognitive terms, the ‘lowering of defences’ may be thought of as a decrease in top-down emotional control. There are several reports in this literature of spontaneous autobiographical recollections or ‘relivings’ under psychedelics – similar in some respects to the dream-like sequences seen on stimulation of the medial temporal lobes or to the flashback phenomena seen in post-traumatic stress disorder (PTSD). In a previous psilocybin functional magnetic resonance imaging (fMRI) study by our group, one individual reported a striking reliving under the drug, further motivating us to test this phenomenon in a controlled manner. We also observed large decreases in resting state activity in the medial prefrontal cortex after psilocybin. The medial prefrontal cortex is known to exert top-down inhibitory control over limbic activity, so a psilocybininduced deactivation of the medial prefrontal cortex – leading to a disinhibition of limbic activity – may explain the occurrence of spontaneous recollections in the psychedelic state. Thus, the present study sought to test the hypothesis that psychedelic drugs facilitate autobiographical recollection, using psilocybin and a blocked fMRI paradigm involving personal memory cues. Spontaneous relivings under psychedelics are often explicitly linked to past traumata; however, we used only positive memory cues in order to minimise the risk of adverse reactions. We predicted that psilocybin would augment subjective and neural responses to personal memories. Based on previous studies implicating medial temporal and visual association regions in vivid autobiographical recollections, we predicted that psilocybin would increase activations in these specific regions.