Abstract:  A major of studies have found that craving plays critical role in nicotine dependence. Cue- exposure is the main paradigm to explore the relationships between nicotine and cravings. Some researchers, however, proposed that this paradigm could not distinguish the episodic and background craving. Consequently, the exact mechanism of craving has not been illustrated clearly. By review of previous studies about craving, we proposed that there exist both similarities and differences between the episodic and background cravings in neural mechanism. More researches should focus on how to separate and identify these two kinds of craving.

Key words: nicotine dependence, smoking, craving, cue-induced, conditioned reflex theory, reward circuit, brain imaging