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Here , the mGlu receptors will be reviewed both in general , and in the particular context of their role in persistent ( > 4 h ) forms of hippocampus - dependent synaptic plasticity and memory , as well as forms of synaptic plasticity that have been shown to be directly regulated by memory events .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None