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We have utilised dissociated primary cortical neuronal cultures , which after 7 days in vitro have formed functional synaptic connections and display periodic and spontaneous synchronised calcium ( Ca ( 2 + ) ) oscillations in response to intrinsic action potential bursts .
 Chemical: calcium; Chemical: Ca ( 2 + )
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: calcium; Chemical: Ca ( 2 + )