In normal mice (left), magenta neurons express the excitatory transmitter glutamate and green neurons express the inhibitory transmitter GABA. Methamphetamine (right) causes glutamate-expressing neurons to express GABA, demonstrated by neurons co-expressing magenta and green labels (arrowheads) in methamphetamine-treated mice but not in untreated mice (normal).

Recognition of objects is a measure of cognition. Having become used to seeing two flowers, the normal mouse (with neurons expressing glutamate) spends more time exploring a new object (a mushroom). After exposure to methamphetamine or PCP (when neurons start expressing GABA), the mouse does not recognize the new object and fails the recognition test. When the change in transmitter is rescued (when neurons are returned to expressing glutamate) the mouse recovers the ability to recognize objects.