▁action ▁potential s ▁that ▁are ▁recorded ▁int rac ell ular ly , ▁but ▁the ▁signals ▁are ▁very ▁much ▁smaller ▁( typ ically ▁about ▁ 1 ▁m V ). ▁Most ▁record ings ▁of ▁the ▁activity ▁of ▁single ▁neur ons ▁in ▁an est het ized ▁and ▁conscious ▁animals ▁are ▁made ▁in ▁this ▁way . ▁Record ings ▁of ▁single ▁neur ons ▁in ▁living ▁animals ▁have ▁provided ▁important ▁ins ights ▁into ▁how ▁the ▁brain ▁processes ▁information . ▁For ▁example , ▁David ▁Hub el ▁and ▁Tor sten ▁Wies el ▁recorded ▁the ▁activity ▁of ▁single ▁neur ons ▁in ▁the ▁primary ▁visual ▁cor tex ▁of ▁the ▁an est het ized ▁cat , ▁and ▁showed ▁how ▁single ▁neur ons ▁in ▁this ▁area ▁respond ▁to ▁very ▁specific ▁features ▁of ▁a ▁visual ▁stim ulus . ▁Hub el ▁and ▁Wies el ▁were ▁awarded ▁the ▁Nobel ▁Prize ▁in ▁Phys i ology ▁or ▁Medicine ▁in ▁ 1 9 8 1 . ▁ ▁Multi - unit ▁recording ▁If ▁the ▁electro de ▁tip ▁is ▁slightly ▁larger , ▁then ▁the ▁electro de ▁might ▁record ▁the ▁activity ▁generated ▁by ▁several ▁neur ons . ▁This ▁type ▁of ▁recording ▁is ▁often ▁called ▁" multi - unit ▁recording ", ▁and ▁is ▁often ▁used ▁in ▁conscious ▁animals ▁to ▁record ▁changes ▁in ▁the ▁activity ▁in ▁a ▁discrete ▁brain ▁area ▁during ▁normal ▁activity . ▁Record ings ▁from ▁one ▁or ▁more ▁such ▁electro des ▁that ▁are ▁closely ▁spac ed ▁can ▁be ▁used ▁to ▁identify ▁the ▁number ▁of ▁cells ▁around ▁it ▁as ▁well ▁as ▁which ▁of ▁the ▁sp ikes ▁come ▁from ▁which ▁cell . ▁This ▁process ▁is ▁called