Using a voltage-sensitive dye, the spatiotemporal dynamics of prefrontal neuronal activity evoked by electrical stimulation of the ventral tegmental area were visualized through optical imaging in anaesthetized rats. Even single-pulse stimulation of the ventral tegmental area elicited a widespread wave of depolarization followed by hyperpolarization in the dorsomedial shoulder region of the prefrontal cortex. We also examined the contribution of dopaminergic transmission to the optical signals by comparing normal and 6-hydroxydopamine-lesioned rats. The 6-hydroxydopamine lesions of ventral tegmental area resulted in a complete absence of depolarization in the prefrontal cortex, although hyperpolarization was preserved. These results indicate that dopaminergic neurons are needed to generate excitatory responses in the prefrontal cortex.