Event-Related Potentials Elicited by a Visual Continuous Performance Task in Children of Alcoholics

EVENT-RELATED POTENTIALS ELICITED BY A VISUAL CONTINUOUS PERFORMANCE TASK IN CHILDREN OF ALCOHOLICS Au ho s: Soco o Rod íguez Holguín, Mon se a Co al and Fe nando Cada ei a This is he pee e iewed e sion o he ollowing a icle: Rod íguez Holguín, S.; Co al, M.; Cada ei a, F. (1999). E en - ela ed po en ials elici ed by a isual con inuous pe o mance ask in child en o alcoholics. Alcohol, 19, 23-30. doi: 10.1016/S0741-8329(99)00013-0 This a icle may be used o non-comme cial pu poses in acco dance wi h Else ie Masson e ms and condi ions o use o sel -a chi ed e sions. Pos -p in ( inal d a pos - e e eeing) 2 EVENT-RELATED POTENTIALS ELICITED BY A VISUAL CONTINUOUS PERFORMANCE TASK IN CHILDREN OF ALCOHOLICS Au ho s: Soco o Rod íguez Holguín, Mon se a Co al and Fe nando Cada ei a Depa men o Clinical Psychology and Psychobiology, Uni e si y o San iago de Compos ela, Galicia, Spain Reques s o ep in s should be add essed o Depa amen o de Psicoloxía Clínica e Psicobioloxía, Facul ade de Psicoloxía, Campus Uni e si a io Su , E-15706, San iago de Compos ela, Galicia, Spain. Tel: + 34-981-563100 (ex . 13798); Fax: + 34-981-521581; E-mail: [email p o ec ed] Pos -p in ( inal d a pos - e e eeing) 3 Abs ac E en - ela ed po en ials (ERPs) we e eco ded om a g oup o young child en o alcoholics (HR; n -17, 7 emales) wi h a high-densi y amily-his o y o alcoholism and om a con ol g oup (CN; n -19, 10 emales), ages 7–15 yea s old, du ing a isual con inuous pe o mance ask. The P3 peak ampli ude and he mean ampli ude a i e la ency windows (300–800 ms) we e measu ed a on al (F3-Fz-F4), cen al (C3-Cz-C4) and pa ie al (P3-Pz-P4) elec odes. Da a we e analyzed using a mixed-model isk-g oup by s imulus- ype (ma ching s. nonma ching) by Elec ode ANCOVA, wi h age as a co a ia e, o each o he scalp egions. The isk-g oup by s imulus- ype in e ac ions we e signi ican a he pa ie al egion o he P3 peak ampli ude and o he 300– 400 ms mean ampli ude, al hough he e we e no isk-g oup main di e ences. The HR g oup mani es ed smalle di e ences be ween he ampli ude o he ma ching and nonma ching condi ion han he CN g oup. These esul s sugges a de icien elec ophysiological di e en ia ion be ween ele an and i ele an in o ma ion and a e discussed in ela ion o p e ious epo s and o he cha ac e is ics o he sample Pos -p in ( inal d a pos - e e eeing) 4 THE ele ance o he s udy o he neu ocogni i e ac o s ela ed o he amilial ansmission o alcoholism is clea om he inc easing numbe o epo s abou his subjec in ecen yea s. Some labo a o ies ha e ocused on he iden i ica ion o psychophysiological and neu opsychological a iables ha would iden i y subpopula ions a inc eased isk o alcoholism and ha e mainly assessed child en o alcoholic a he s. One a ea o in es iga ion has e alua ed he e ec s o acu e alcohol adminis a ion on hese a iables. Alcohol has di e en ial e ec s on child en o alcoholics o e au onomic a iables in esponse o s ess ul o no el s imuli, wi h hese subjec s appea ing mo e sensi i e o he s ess-dampening e ec s o alcohol (12,17). Wi h ega d o CNS measu es, a pionee ing s udy (14) ound ha adul child en o alcoholics we e mo e sensi i e han con ols o he e ec o acu e alcohol adminis a ion on he P3 componen o he ERPs du ing a en ion asks, and di e ences in o he e en - ela ed po en ial (ERP) componen s (e.g., N100) ha e also been epo ed (5). Di e en ial e ec s o alcohol on neu opyschological es s pe o mance ha e also been s udied, al hough he esul s a e less consis en (18,25). O he in es iga ions ha e s udied he di e ences be ween heal hy child en o alcoholics and con ols wi hou alcohol adminis a ion. They ha e he ad an age o allowing he assessmen o young, alcohol-nai e subjec s, o sea ch o a iables ha cha ac e ize subjec s a isk o alcoholism wi hou in e ac ion wi h consump ion. Biochemical (se o onin me aboli es, MAO-B), psychophysiological [hea a e, elec ode mal esponse, elec oencephalog aphic (EEG), ERPs], neu opsychological ( isuospa ial abili ies, a en ion, memo y, planning), beha io al (hype ac i i y, conduc p oblems) and pe sonali y (sensa ion seeking, ewa d dependence) a iables ha e been s udied and e iewed in li e a u e (15,25,28). One impo an b anch o his a ea o esea ch is ha ocused on unc ioning in child en o alcoholics. Beglei e and colleagues epo ed ha young sons o alcoholic a he s mani es ed a diminished ol age in he P3 componen o he isual ERPs, in he same way as alcoholic subjec s (6). Subsequen ly, se e al o he labo a o ies ha e assessed he P3 componen o ERPs elici ed by isual and audi o y asks wi h di e en le els o di icul y, wi h samples composed o young and adul child en o alcoholics. In 1994, a me a-analysis s udy o 22 epo s ha compa ed he P3 o non-alcoholic subjec s wi h and wi hou a amily his o y o alcoholism was published (20). I lead o he conclusion ha he P3 ol age is smalle in subjec s a amily isk o alcoholism and sugges ed ha se e al mode a o ac o s con ibu e o explaining disc epan indings among labo a o ies. The age o he samples, he senso y modali y assessed, and he di icul y o he asks used o elici P3 appea ed o be he p incipal mode a ing ac o s. Polich and co-wo ke s s a ed ha di e ences be ween he isk and con ol g oups a e mo e obus when di icul isual asks a e used o assess young subjec s ( 20). None heless, hey also ecommended o pay a en ion in u u e empi ical s udies o o he ac o s such as he sou ce o ec ui men , he p esence o addi ional Axis I o Axis II diso de s in he amilies, o he neu opsychological pe o mance in a en ion and memo y p ocesses. The ele ance o hese ac o s has also been poin ed ou by Beglei e and Po jesz (5). In addi ion, wo ecen ollow-up s udies (9,16) poin ha ERP abno mali ies in childhood appea use ul as good p edic o s o adolescen alcohol and d ugs abuse. In ou labo a o y, young child en o alcoholics we e classi ied acco ding o he p esence o absence o a mul igene a ional amily his o y o alcoholism; hose wi h o he psychopa hological diseases in i s - o second-deg ee ela i es we e excluded. They we e assessed wi h a se o pa adigms wi h a ying le els o di icul y o elici se e al ERP componen s, as well as wi h a Pos -p in ( inal d a pos - e e eeing) 5 ba e y o neu opsychological es s. When an easy disc imina ion isual ask was employed, he P3 elici ed by a a ge had lowe ampli ude and longe la ency only in he emale subg oup wi h a mul igene a ional amily his o y o alcoholism, bu he e we e no di e ences wi h he con ol g oup o he males (23). The P3 elici ed by he in equen non a ge s imuli did no di e in ampli ude be ween child en o alcoholics and con ols, al hough la ency di e ences we e obse ed (22). In he p esen epo , ERPs we e assessed using a mo e complex isual ask. The pa adigm used eplica es he con inuous pe o mance ask as implemen ed by Noble and colleagues (8,26,27). This pa adigm was selec ed because i in ol es a mo e complex p ocessing o s imuli han disc imina ion asks. As s a ed abo e, his has been conside ed a mode a ing ac o o di e ences in ERPs be ween child en o alcoholics and con ols (20). Mo eo e , his pa adigm has been used by Whipple and colleagues o s udy he ela ionship be ween elec ophysiological measu es and neu opsychological achie emen in isuope cep ual and memo y es s (26). Me hod Subjec s The subjec s we e 36 males and emales anging om 7 o 15 yea s o age. The high- isk (HR) g oup (n =17, 7 emales, mean =11.8 +- 2.3 y ) consis ed o child en o alcoholic a he s wi h a high densi y amily his o y o alcoholism. The subjec s in he HR g oup we e selec ed om communi y ea men cen es, whe e hei a he s had been diagnosed and ea ed. All he alcoholic a he s me DSM-III-R (2) c i e ia o alcohol dependence. (A diagnosis made by he s a o he cen es was co obo a ed du ing he selec ion in e iew.) Those wi h a his o y o psychopa hological p oblems o he han seconda y o alcoholism (acco ding o he clinical his o y om he cen es and he in o ma ion collec ed du ing he selec ion in e iew) we e excluded. The amily his o y o alcoholism was asce ained om a he s and mo he s using he amily his o y in e iew me hod. Only child en o alcoholic a he s who had a leas wo o he i s - o second- deg ee alcoholic ela i es we e included. The con ol (CN) g oup ( n = 19, 10 emales, mean = 12.0 +- 1.7 y ) consis ed o child en o non alcoholic a he s wi hou a amily his o y o alcoholism. To gua an ee homogenei y wi h ega d o sociodemog aphic a iables, con ol subjec s we e ec ui ed om olun a y amilies om schools in he egion wi hin he same age ange and socioeconomic s a us as hose in he HR g oup. Con ol amilies who epo ed any p oblems wi h alcohol in i s - o second- deg ee ela i es we e excluded. O he exclusiona y c i e ia we e simila o he wo g oups and included consump ion o alcohol o o he d ugs, a his o y o psychopa hological diso de s, p ena al exposu e o alcohol, de elopmen al o school e a da ion, a posi i e neu ological his o y, majo medical p oblems, cu en medica ion, nonco ec ed senso y de ici s, a amily his o y o majo men al diseases, and p oblems o alcoholism in he mo he . In o ma ion abou inclusion and exclusion c i e ia was ob ained h ough de ailed semi-s uc u ed in e iews wi h bo h he child en and hei a he s and mo he s. The in e iews we e a ansla ed and adap ed e sion o he Semi-S uc u ed Assessmen o he Gene ics o Alcoholism e sions o adul s, child en, adolescen s, and pa en s, as well as he Family His o y Assessmen Module, designed by he Collabo a i e S udy on he Gene ics o Alcoholism (11). Ques ions abou indi idual and amilial psychopa hological p oblems we e based on DSMIII- R c i e ia and a leas one o he diagnos ic classi ica ion sys em. In o ma ion Pos -p in ( inal d a pos - e e eeing) 6 was also ob ained du ing he in e iews abou demog aphic da a, amily ela ions, school achie emen and social ac i i ies. The inal sample was well ma ched o age, handedness, socio-economic s a us and educa ion— all subjec s we e en olled in compulso y schooling and ollowed he g ade acco ding o age— be ween he g oups (see Table 1). Subjec s om he wo g oups we e andomly dis ibu ed ac oss en i onmen al a iables such as ERPs assessmen ime ( ime o day, mon h), o ecency o ood inges ion (19). Families who me he equi emen s o he s udy we e asked o pa icipa e; hose who ag eed signed a consen o m and ecei ed an appoin men o he assessmen . When he child en a i ed a he labo a o y (ea ly in he mo ning o in he a e noon), he membe s o s a showed hem he labo a o y and explained he con en s and p ocedu e o he assessmen . Once elec odes had been pu in place, subjec s sa in a com o able a mchai , in an elec ically isola ed, sound- and ligh -a enua ed labo a o y. They ecei ed gene al ins uc ions o a oid mo ing du ing he es and o pay a en ion o he ins uc ions abou he ask. The isual con inuous pe o mance ask is a eplica o ha designed by Noble e al. (26). Subjec s we e ins uc ed o wa ch o a ideo moni o placed 1 m in on o hem, whe e isual s imuli we e p esen ed. The s imuli, p esen ed one a a ime, a a cons an ISI (onse -onse ) o 2.1 s wi h a du a ion o 100 ms sub ended a isual a ea o 4.8º X 4.8º. The s imuli a ied in h ee dimensions: shape, colo , and he iden i y o a nume al in he cen e o each shape. Ci cles, squa es, and iangles, which we e ei he o ange, blue, g een, o iole and con ained a nume al be ween 0 and 9, we e used. Subjec s had o p ess a bu on wi h he p e e ed hand when wo consecu i e s imuli ma ched in all he h ee s imulus dimensions. The se ies consis ed o 200 s imuli, wi h ma ches occu ing pseudo- andomly wi h he only es ic ion o no wo ma ches appea ing consecu i ely, and a p obabili y o 0.11 ( n= 22 ma ches). ERP Reco ding EEG ac i i y was eco ded a nine scalp si es: Fz, F3, F4, Cz, C3, C4, Pz, P3, and P4 (s anda d elec ode posi ion nomencla u e)(1), using in elec odes inse ed in an elec ocap (Elec o-Cap In e na ional, Inc.), e e ed o linked ea lobes,and wi h a o ehead g ound. Addi ional elec odes we e used o moni o eye mo emen s (sup ao bi al and he ou e can hus o he le eye, e e ed o an in ao bi al elec ode). EEG ac i i y was il e ed (0.1–30 Hz) and ampli ied 10 K(G ass Neu oda a Acquisi ion Sys em, model 12, connec ed o a Neu o Scan, Inc. sys em o he analogue- o-digi al con e sion and s o age). Impedance alues we e kep a 5KV o below. EEG was con inuously sampled a a a e o 256 Hz. The signal was p ocessed o -line. Fi s , EEG was co ec ed o ocula a e ac s, using he algo i hm de eloped by Semli sch and colleagues (24); hen EEG was epoched om 100 ms p es imulus o 900 ms pos s imulus, linea ends we e elimina ed, and he signal was adjus ed o 0m V p es imulus baseline. T ials exceeding 685 m V a any scalp elec ode we e iden i ied by isual inspec ion and ejec ed. The epochs co esponding o inco ec esponses (omissions o alse ala ms) we e also ejec ed. Finally, ials we e a e aged acco ding o ype o s imuli (ma ches and nonma ches), and digi al il e ing was pe o med o - line using a 0.1–16 Hz band-pass il e . Only hose subjec s ( n=36) wi h a leas 15 epochs o he a e aged wa e o m elici ed by ma ches we e included in he s udy; 14 subjec s om he ini ial sample (se en a each isk g oup) we e d opped because o less han 15 epochs emained o Pos -p in ( inal d a pos - e e eeing) 7 a e aging. The numbe o a ge epochs in he HR (mean =18.1 +- 2.3, ange =15–22) and he CN (mean= 18.0 +- 1.8, ange 15–22) g oups did no di e ( = 0.10, p . 0.924). Da a Analysis ERPs we e au oma ically measu ed o bo h he ma chingand he nonma ching eco dings, as he mean ampli udes in i e 100 ms pos s imulus in e als: 300–400, 400–500, 500–600, 600– 700, and 700–800 ms. P3 peak ampli ude was also measu ed, and iden i ied, using a compu e algo i hm, as he maximum posi i e peak a each elec ode be ween 400 and 600 ms; peaks we e hen e i ied and adjus ed by isual inspec ion, and hose which we e doub ul we e e ised by a second expe ienced membe o he labo a o y,blind o he isk s a us o he subjec and he ini ial peak. Ampli ude alues we e au oma ically expo ed o an ASCII ile o subsequen analyses. The ERP measu emen s we e o ganised in o h ee elec ode g oupings: on al (F3, F4, Fz), cen al (C3, C4, Cz), and pa ie al (P3, P4, Pz). P elimina y isk g oup by gende and isk g oup by age analyses we e made o de e mining he inclusion o gende and age a iables in he design. As he e we e no signi ican in e ac ions in hese analyses and no signi ican di e ences be ween males and emales, bo h gende s we e conside ed join ly, and age was included as a co a ia e. The e o e, a 2 X 2 X 3, isk g oup (CN s. HR) by s imulus ype (ma ching s. nonma ching) by elec ode mixed-model ANCOVA, wi h he isk g oup as a be ween-subjec s ac o , he s imulus- ype and he elec ode as wi hin-subjec ac o s, and age as a co a ia e we e used o assess g oup di e ences in he ERPs mean ampli ude a each ime in e al and in he P300 peak ampli ude in each o he elec ode g oupings. Deg ees o eedom we e co ec ed by he conse a i e G eenhouse- Geisse es ima e when app op ia e. Mo eo e , o a oid ha isk g oup di e ences a indi idual elec odes may bemasked by egional analyses, hose elec odes whe e he P3 componen is mo e equen ly assessed, Pz and Cz we e sepa a ely analyzed, using a isk g oup by s imulus- ype ANCOVA. Beha iou al da a ( esponse ime and pe cen age o co ec esponses) we e assessed using an ANCOVA compa ison be ween he isk g oups wi h age as a co a ia e. Resul s Beha io al Pe o mance Table 2 summa izes he beha io al da a o each g oup. No signi ican di e ences be ween he isk g oups we e obse ed o esponse ime and pe cen age o co ec esponses ( p . 0.05). ERP Measu emen s Figu e 1 illus a es he g and mean wa e o ms o he wo isk g oups in he wo s imulus ypes a each o he elec odes eco ded. The desc ip i e es a is ics o he da a a e summa ized in Table 3. The isk g oup be ween-subjec s ac o mani es ed no signi ican di e ences a any o he mean ampli ude in e als o he P3 peak ampli ude alues. The s imulus- ype wi hin-subjec s ac o was signi ican o e he whole sample a he pa ie al egion (P3, Pz, P4) o all he mean ampli ude in e als excep he 300–400 and he 700–800 ms in e als: 400–500 ms: F (1, 34) =7.74, p <0.009; 500–600 ms: F (1, 34) = 21.83, p < 0.0005; 600– Pos -p in ( inal d a pos - e e eeing) 8 700 ms: F (1, 34) = 22.15, p <0.0005. A he cen al egion (C3, Cz, C4) his ac o was signi ican o all excep he 700–800 ms mean ampli ude in e al: 300–400 ms: F (1, 34) = 7.18, p <0.011; 400–500 ms F(1, 34) =7.64, p<0.009; 500–600 ms: F(1, 34)= 15.62, p <0.0005; 600–700 ms:F (1, 34) = 11.22, p <0.002. Finally, a he on al egion (F3, Fz, F4) i was signi ican only o he ea lie mean ampli ude in e als: 300–400 ms: F (1, 34)=13.17, p < 0.001; and 400–500 ms: F (1, 34) = 8.29, p < 0.007. The P3 peak ampli ude was signi ican ly di e en o he ma ching and he non-ma ching s imuli a he pa ie al [ F (1, 34) =32.69, p <0.0005], cen al [ F (1, 34)= 23.19, p<0.0005], and on al [ F (1, 34) = 17.54, p < 0.0005] egions. In all hese a iables, he ampli udes elici ed by he ma ching s imuli we e la ge han hose elici ed by he nonma ching s imuli. The isk g oup by s imulus- ype in e ac ions we e signi ican only a he pa ie al egion o he 300–400 ms mean ampli ude in e al [ F (1, 34) = 4.75, p < 0.036] and o he P3 peak ampli ude a he same scalp egion [ F (1, 34) = 5.59, p < 0.024]. To cla i y he meaning o in e ac ions, simple e ec s analyses we e made. The compa ison o he wo s imulus ypes sepa a ely o each isk g oup indica ed ha , o he 300–400 ms mean ampli ude in e al, he ERPs elici ed a he pa ie al egion by he ma ching s imuli we e la ge han hose elici ed by he nonma ching s imuli in he CN g oup [ F (1, 18) = 4.70, p < 0.044], bu he e we e no s imulus- ype di e ences in he HR g oup [ F (1, 16) = 0.82, p < 0.380]. Wi h ega d o he P3 pa ie al ampli ude, he s imulus- ype compa isons we e signi ican o bo h he CN [ F (1, 18) = 30.74, p <0.0005] and he HR [F(1, 16) = 6.20, p < 0.024] g oups, al hough he di e ence be ween he ampli ude o he ma ching and he nonma ching condi ion was smalle in he HR han in he CN g oup [F(1, 33) = 5.54, p <0.025] (see Figu e 2). The elec ode wi hin-subjec ac o was signi ican (p <0.05) a he h ee scalp egions and he i e mean ampli ude in e als excep o he on al elec ode g ouping a he 500– 600 ms and he 700–800 ms in e als, and o he pa ie al elec ode g ouping a he 700–800 ms in e al. F on al egion: 300–400 ms: F(2, 68) = 3.47, p < 0.037; 400–500 ms: F(2, 68) =4.06, p<0.022; 600–700 ms: F(2, 68) = 4.45, p < 0.015. Cen al egion: 300–400 ms: F(2, 68) = 10.96, p < 0.0005; 400– 500 ms: F(2, 68) = 11.14, p<0.0005; 500–600 ms: F(2, 68) = 9.22, p<0.0005; 600–700 ms: F(2, 68) = 10.38, p < 0.0005; 700–800 ms: F(2, 68)= 18.18, p <0.0005. Pa ie al egion: 300–400 ms: F(2, 68) = 6.70, p < 0.002; 400–500 ms: F(2, 68) = 15.56, p <0.0005; 500–600 ms: F(2, 68) = 24.35, p<0.0005; 600–700 ms: F(2, 68) = 15.82, p <0.0005. The elec ode ac o was also signi ican o he P3 peak ampli ude a he cen al [F(2, 68) = 18.67, p < 0.0005] and pa ie al [F(2, 68) = 25.58, p <.0005] egions. The elec ode di e ences e lec ed ha he maximum ampli udes we e eco ded a he midline elec odes in he h ee egions (Pz, Cz, Fz) compa ed wi h he la e al elec odes. The isk g oup by elec ode in e ac ions we e no signi ican o any o he dependen a iables conside ed a his epo . Finally, he co a ia e (age), was signi ican a he ollowing a iables: Pa ie al: 300–400 ms (p< 0.010); 400–500 ms (p < 0.019); 700–800 ms (p<0.010). Cen al: 300–400 ms (p <0.0005); 400– 500 ms (p < 0.003); 600–700 ms (p < 0.048); 700– 800 ms (p < 0.0005). F on al: 300–400 ms (p < 0.0005); 400– 500 ms (p < 0.008); 600–700 ms (p < 0.012); 700–800 ms (p < 0.027). P3 ampli ude a cen al (p < 0.038) and on al (p <0.021) egions. The ampli ude inc eased wi h age o all hese Pos -p in ( inal d a pos - e e eeing) 9 a iables. A eanalysis wi hou co a ia e in hose cases, whe e i was no signi ican , did no modi y he signi icance o he o he ac o s. Cz and Pz Sepa a e Analyses The indi idual analyses o Cz and Pz con i med he e ec s obse ed in he egional analyses. The e we e no Risk G oup main e ec s o Risk G oup by Condic ion in e ac ions o any o he ampli ude a iables a he Cz elec ode. The Risk G oup by Condi ion in e ac ion was signi ican o 300–400 ms ampli ude [F(1, 34)= 5.55, p < 0.024] and o he P3 peak ampli ude [F(1, 34)=6.54, p < 0.015] a Pz, due o he smalle di e ences be ween ma ching and nonma ching ampli ude in he HR g oup. Discussion In his s udy, he o e all measu es o ERP ampli udes we e no di e en be ween child en o alcoholic a he s wi h a mul igene a ional amily his o y o alcoholism and con ols, al hough signi ican di e ences in ol ing he isk g oup ac o appea ed in he in e ac ion wi h he s imulus ype (ma ching s. nonma ching condi ion) in he pa ie al egion, a ec ing he P3 peak ampli ude and he mean ampli ude in he 300–400 ms in e al. The main e ec s o he wi hin-subjec s ac o s, elec ode and s imulus condi ion we e hose expec ed in his pa adigm: maximum ampli udes a he midline elec odes in all he scalp egions and la ge ampli udes elici ed by he ma ching han he nonma ching s imuli. These esul s a ec ing he isk g oups should be discussed in ela ion o he p e ious gene al li e a u e ha has epo ed a diminished ol age in he P3 o child en o alcoholics bu speci ically in ela ion o he esul s using he same pa adigm wi h o he samples (bea ing in mind ha he p e ious esul s used o he pa adigms wi h his sample). The i s epo by Whipple e al. (26) using he pa adigm eplica ed he e compa ed he mean ampli ude o he ERPs o he ma ching s imuli a 300–400, 400–500 and 500–600 ms la ency windows a Fz, Cz, and Pz elec odes. They ound ha subjec s wi h a amily his o y o alcoholism mani es ed smalle ampli udes a he 300– 400 and 400–500 ms la ency windows a he h ee elec odes. Subsequen epo s om he same labo a o y con i med he p esence o di e ences be ween high- isk young subjec s and con ols. In a la e s udy (27), esea che s ound educed ampli udes and elonga ed la encies o he P3 elici ed by he ma ching s imuli a Pz, al hough he o e all compa ison, including he wo s imulus condi ion and i e elec odes, had been no-signi ican o he P3 ampli ude and he slow wa e mean ampli ude. Wi h a new sample and a mo e de ailed analysis (8), hese au ho s a e aged he ERPs acco ding o he numbe o ma ching ea u es and ound no signi ican main e ec s o he g oup ac o bu a signi ican g oup by s imulus condi ion (ma ch le el) in e ac ion o 500 o 800 ms. The e o e, al hough no main g oup di e ences in ampli ude we e obse ed, he esul s p esen ed he e a e no disc epan wi h hose p e iously ob ained wi h he same pa adigm. As may be seen in Figu e 2, he isk g oup by s imulus in e ac ion was due o a lesse di e en ia ion be ween he ol age o he ma ching and he nonma ching wa e o ms in he high- isk g oup. This is a simila pa e n o ha desc ibe by Be man and colleagues (8) and would co obo a e he hypo hesis ha subjec s a isk o alcoholism a e less able o di e en ia e, a an elec ophysiological le el, be ween ele an and i ele an in o ma ion. I he P3-like posi i e componen s o ERPs a e Pos -p in ( inal d a pos - e e eeing) 16