- Effects of the 5-HT2A agonist psilocybin on mismatch negativity generation and AX-continuous performance task: implications for the neuropharmacology of cognitive deficits in schizophrenia. Umbricht, D., Vollenweider, F.X., Schmid, L., Grübel, C., Skrabo, A., Huber, T., Koller, R. Neuropsychopharmacology (2003)