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The prefrontal cortex ( PFC ) is thought to be critically involved in the modulation of executive function and these attentional processes are enhanced by nicotine acting at nicotinic acetylcholine receptors .
 Chemical: nicotine; Chemical: acetylcholine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: nicotine; Chemical: acetylcholine