19855
When we explored the neural substrates of acupuncture on the modulation of cravings induced by smoking cues , significant differences were found in the medial prefrontal cortex , the premotor cortex , the amygdala , the hippocampus , and the thalamus .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None