▁According ▁to ▁Burg ess ▁et ▁al ., ▁" The ▁n - back ▁task ▁is ▁typically ▁thought ▁to ▁require ▁the ▁updating ▁of ▁information ▁in ▁WM , ▁because , ▁for ▁each ▁sequ entially ▁presented ▁item , ▁the ▁particip ant ▁must ▁judge ▁whether ▁it ▁matches ▁the ▁item ▁presented ▁n ▁tri als ▁back ▁( where ▁n ▁is ▁pres pec ified , ▁and ▁usually ▁equals ▁ 1 , ▁ 2 , ▁or ▁ 3 ▁items ). " ▁ ▁While ▁inside ▁the ▁M RI ▁machine , ▁subjects ▁are ▁asked ▁to ▁complete ▁a ▁variety ▁of ▁tasks . ▁The ▁brain ▁activity ▁is ▁then ▁captured ▁and ▁recorded ▁by ▁using ▁M RI , ▁allowing ▁specific ▁brain ▁responses ▁to ▁be ▁pa ired ▁with ▁their ▁respective ▁n - back ▁tasks . ▁ ▁Ne uro im aging ▁techniques ▁ ▁P ET ▁ ▁Pos it ron ▁emission ▁tom ography ▁detect s ▁g amma ▁ray s ▁as ▁they ▁are ▁em itted ▁from ▁a ▁trac er ▁that ▁has ▁been ▁inject ed ▁into ▁the ▁body . ▁It ▁is ▁useful ▁in ▁ne uro im aging ▁because ▁of ▁the ▁assumption ▁that ▁areas ▁of ▁high ▁radio activity ▁are ▁associated ▁with ▁high ▁brain ▁activity . ▁ ▁C AT ▁Sc an ▁ ▁Comput ed ▁ax ial ▁tom ography ▁( CAT ) ▁or ▁computed ▁tom ography ▁( CT ) ▁creates ▁tom ographic ▁images ▁of ▁the ▁body . ▁For ▁ne uro im aging ▁studies , ▁computer - process ed ▁X - ray s ▁are ▁used ▁and ▁the ▁amount ▁of ▁X - ray ▁block age ▁by ▁different ▁structures ▁is ▁used ▁to ▁generate ▁image ▁' s lices ' ▁of