This relates to methods for the detection of psychoactive compounds in an in vitro neuronal tissue sample by detecting oscillations of extracellular voltage desirably before and after the introduction of a candidate sample onto an in vitro neuronal tissue sample and for devices useful in practicing the methods. Analysis of the extracellular voltage parameters leads to indication of the presence of psychoactive material in the candidate sample and information as to its pharmacological activity and/or composition. Further, it relates to a process of initiating and maintaining the presence of repetitive neuronal activity within the in vitro sample. Additionally, this includes a method for the stimulation of or initiation of repetitive neuronal activity, e.g., EEG, in an in vitro neuronal tissue sample by introducing a stimulating composition comprising compounds that facilitate or mimic the actions of acetylcholine, serotonin, or catecholamines, such as carbachol, or by subjecting the in vitro neuronal sample to electrical stimulation parameters.