s ▁efficiency ▁of ▁communication ▁with ▁a ▁posts yn apt ic ▁cell . ▁Thus , ▁because ▁the ▁inter neur on ▁does ▁not ▁specifically ▁activ ate ▁the ▁posts yn apt ic ▁neur on ▁( str ength ▁in ▁its ▁syn apt ic ▁pl astic ity ▁is ▁indirect ly ▁affected ), ▁this ▁mechanism ▁of ▁mod ul atory ▁input - dependent ▁pl astic ity ▁is ▁heter os yn apt ic . ▁To ▁better ▁understand ▁this ▁process ▁and ▁its ▁vast ▁divers ity , ▁key ▁functions ▁of ▁the ▁neur om od ulator ▁ser ot on in ▁in ▁Ap ly s ia ▁cal iforn ica ▁and ▁dop am ine ▁are ▁further ▁illustrated . ▁ ▁Ap ly s ia ▁cal iforn ica ▁ ▁The ▁classic ▁example ▁that ▁demonstr ates ▁mod ul atory ▁input - dependent ▁pl astic ity ▁involves ▁the ▁marine ▁m oll usk , ▁Ap ly s ia ▁cal iforn ica . ▁Studies ▁in ▁the ▁late ▁ 1 9 6 0 s ▁provided ▁the ▁first ▁evidence ▁for ▁pl astic ity ▁in ▁the ▁chemical ▁syn aps es ▁of ▁Ap ly s ia . ▁These ▁studies ▁showed ▁that ▁several ▁types ▁of ▁mod ul atory ▁inter neur ons ▁were ▁excited ▁in ▁the ▁sens ory ▁and ▁motor ▁neur on ▁circuit ▁of ▁Ap ly s ia . ▁In ▁Ap ly s ia , ▁stim ulation ▁of ▁the ▁si phon ▁sens ory ▁neur on ▁terminal s ▁led ▁to ▁an ▁en hanced ▁EP SP ▁in ▁the ▁mod ul atory ▁inter neur on . ▁The ▁mod ul atory ▁inter neur ons ▁release ▁ser ot on in , ▁which ▁triggers