The slice preparation or brain slice is a laboratory technique in electrophysiology that allows the study of a synapse or neural circuit in isolation from the rest of the brain, in controlled physiological conditions. It involves stimulating and/or recording from a slice of brain tissue immersed in artificial cerebrospinal fluid. The technique allows for greater experimental control, through elimination of the effects of the rest of the brain on the circuit of interest, careful control of the physiological conditions through perfusion of substrates through the incubation fluid, to precise manipulation of neurotransmitter activity through perfusion of agonists and antagonists. However, the increase in control comes with a decrease in the ease with which the results can be applied to the whole neural system.