▁sp ike ▁sorting ▁and ▁is ▁suitable ▁in ▁areas ▁where ▁there ▁are ▁identified ▁types ▁of ▁cells ▁with ▁well ▁defined ▁sp ike ▁characteristics . ▁If ▁the ▁electro de ▁tip ▁is ▁bigger ▁still , ▁in ▁general ▁the ▁activity ▁of ▁individual ▁neur ons ▁cannot ▁be ▁distinguished ▁but ▁the ▁electro de ▁will ▁still ▁be ▁able ▁to ▁record ▁a ▁field ▁potential ▁generated ▁by ▁the ▁activity ▁of ▁many ▁cells . ▁ ▁Field ▁potential s ▁ ▁Ext rac ell ular ▁field ▁potential s ▁are ▁local ▁current ▁s inks ▁or ▁sources ▁that ▁are ▁generated ▁by ▁the ▁collect ive ▁activity ▁of ▁many ▁cells . ▁ ▁Usually , ▁a ▁field ▁potential ▁is ▁generated ▁by ▁the ▁simultane ous ▁activation ▁of ▁many ▁neur ons ▁by ▁syn apt ic ▁transmission . ▁ ▁The ▁diagram ▁to ▁the ▁right ▁shows ▁hi pp oc amp al ▁syn apt ic ▁field ▁potential s . ▁ ▁At ▁the ▁right , ▁the ▁lower ▁trace ▁shows ▁a ▁negative ▁wave ▁that ▁corresponds ▁to ▁a ▁current ▁sink ▁caused ▁by ▁positive ▁charges ▁entering ▁cells ▁through ▁posts yn apt ic ▁gl ut am ate ▁re cept ors , ▁while ▁the ▁upper ▁trace ▁shows ▁a ▁positive ▁wave ▁that ▁is ▁generated ▁by ▁the ▁current ▁that ▁leaves ▁the ▁cell ▁( at ▁the ▁cell ▁body ) ▁to ▁complete ▁the ▁circuit . ▁ ▁For ▁more ▁information , ▁see ▁local ▁field ▁potential . ▁ ▁Am per ometry ▁Am per ometry ▁uses ▁a ▁carbon ▁electro de ▁to ▁record ▁changes ▁in ▁the ▁chemical ▁composition ▁of ▁the ▁ox id ized ▁components ▁of ▁a ▁bi ological ▁solution . ▁Ox id ation ▁and ▁reduction ▁is ▁accomplished ▁by ▁changing ▁the