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실어증환자의단기기억및작업기억용량과실어증중증도및문장처리와의상관 성지은 이화여자대학교언어병리학과 교신저자성지은이화여자대학교언어병리학과교수, 서울특별시서대문구대현동 11-1 진선미관 217호 e-mail: jeesung@ewha.ac.kr tel.: 02-3277-2208 배경및목적 : 실어증환자들의단기기억 (short-term memory) 및작업기억용량 (working memory capacity) 의개인차에따른실어증중증도및문장처리능력차이에관한연구가주목을받고있다. 하지만, 정상인을대상으로개발된산출을기반으로하는기억기제평가방법을실어증환자들에게직접적으로적용하는데는다양한문제가제기될수있다. 따라서본연구에서는기존에사용되던단기및작업기억과제 (Martin, Kohen & Kalinyak-Fliszar, 2008) 를지시하기폭과제 (pointing span task) 로변형한후, 숫자및단어로자극양상을조절하여과제별수행력차이를살펴보았으며, 기억과제들과실어증중증도및문장처리능력에관한상관관계를분석하였다. 방법 : 대상자는영어를모국어로사용하는실어증환자 20 명과정상노인 30 명이다. 단기기억과제로는숫자및단어바로따라지시하기과제가사용되었으며, 작업기억과제로는숫자및단어거꾸로따라지시하기과제를사용하였다. 실어증중증도는 Porch Index of Communicative Ability (PICA) 를통해평가되었으며, 문장처리능력은 Computerized Revised Token Test (CRTT) 를사용하여살펴보았다. 결과 : 두집단모두단기기억과제에비해작업기억과제에서더낮은수행력을보였으며, 숫자에비해단어에서더어려움을보였다. 두집단간의차이가가장크게나타나는과제는숫자거꾸로따라지시하기과제였다. 주성분분석결과에따르면, 네가지기억과제는하나의공통적인성분으로추출될수있으며, 총분산의 80% 가량을설명하는것으로나타났다. 논의및결론 : 네가지기억과제의공통적인기제를개념화하자면, 짧은시간동안정보를저장하거나조작하는데기여하는인지적기제라고할수있다. 네가지기억과제중, 실어증중증도와실어증환자의문장처리수행력을유의하게예측한변수는숫자바로따라지시하기과제였다. 작업기억용량이론에바탕을둔결과해석이논의되었으며한국어를사용하는실어증환자를위한작업기억과제개발에대한필요성도제기되었다. 언어청각장애연구, 2010;15;285-297. 핵심어 : 단기기억, 작업기억, 지시하기폭과제, 실어증중증도, 문장처리 Ⅰ. 서론 실어증환자들을대상으로최근다양한언어적단기기억 (linguistic short-term memory) 및작업기억 (linguistic working memory) 과제등을사용하여실어증환자들의문장이해와기억기제 (memory mechanism) 와의관련성을연구하는논문들이꾸준히증가하고있다 (Caplan & Waters, 1995; Caspari et al., 1998; Ivanova & Hallowell, 2010; Sung et al., 2009; Tompkins et al., 1994). 작업기억이란단기기억을바탕으로하는짧은지속시간내에정보를저장할수있는공간과더불어정보를처리 (processing) 및조작 (computational or operational) 하는데기여하는인지적기제를말한다 (Baddeley & Hitch, 1974). Baddeley & Hitch (1974) 가처음제시한작업기억모델은크게세가지요소로구분된다. 우선음운루프 (phonological loop) 로서음운되내기 (phonological rehearsal) 과정을통해단기적으로정보를저장하는 게재신청일 : 2010 년 7 월 20 일 최종수정일 : 2010 년 8 월 30 일 게재확정일 : 2010 년 9 월 5 일 c 2010 한국언어청각임상학회 http://www.kasa1986.or.kr 285

언어청각장애연구 2010;15;285-297 공간과시공간스케치패드 (visuospatial sketchpad) 로서시공간적정보를처리하는공간을들수있다. 마지막으로이두가지요소를모두관장하는총제적인인지기제로서중앙집행기 (central executive) 를작업기억를구성하는세가지요소중하나로제시하였다. 보다최근 Baddeley (2000) 는네번째작업기억요소로서일화적완충장치 (episodic buffer) 를추가하였는데, 이는장기기억체계 (long-term memory system) 와의상호작용을단기적정보유지및조작을바탕으로하는작업기억체계에추가하였다는데의미가있다. Baddeley의작업기억요소들중, 언어와관련하여가장주목을받은하위요소는음운루프로서이요소를강조하여음운작업기억 (phonological working memory) 이라는용어로사용되기도한다. 하지만, 보다최근에는중앙집행기의기능에중점을두는연구들이다양화되고있다. 작업기억연구초기에는중앙집행기를 개념적잡동사니모음 (conceptual ragbag) 이라고말하며작업기억체계중 잔여무지영역 (the area of residual ignorance) 이라고하여중앙집행기라는용어가구체적으로명시되지않은개념으로쓰이고있음을인정하였으나 (Baddeley, 1986, p. 224-225), 보다최근에는중앙집행기에대한다양한조작적정의가등장하며이요소를부각하는이론과연구가다양화되었다. Just & Carpenter (1992) 가작업기억용량이론 (working memory capacity theory) 을발표하며 Baddeley의작업기억요소중중앙집행기는본격적으로주목받기시작하였다. Just & Carpenter (1992) 에따르면, 작업기억용량이란 단기적인정보유지및조작을지지하는데최대이용가능한활성화용량 (the maximum amount of activation available in working memory to support either of the two functions (p. 123) 이라고정의하였다. 이러한개념은 Engle, Kane과동료들에게로이어져작업기억은정보의단순저장고로서의역할만강조하는단기기억 (shortterm memory) 과는분명한대조를이루고있음을강조하는근거를제시하기에이른다 (Cowan, 1988; 1995; Engle, 2001; 2002; Engle & Kane, 2004; Engle et al., 1999; Kane & Engle, 2000; 2003; Kane et al., 2006). 즉, 잠재변수분석 (latent variable analysis) 및구조방정식모델 (structural equation modeling) 을사용하여단기기억과작업기억의공통분산 (shared variance) 을통계적으로통제한후, 작업기억의잔차분산 (residual variance) 과일반유동적지능 (general fluid intelligence) 과의관계를살펴보았다. 작업기억의잔차분산은 Raven s Progressive Matrices (Raven, Court & Raven, 1977) 또는 Cattell s Culture Fair Test (Cattell, 1973) 과제와유의한상관관계를보였으나, 단기기억은이러한일반유동적지능을나타내는과제와유의한상관관계를보이지않았다. 이를근거로작업기억은단기기억과는구별되는개념으로서, 과제를유지및조작하는능력과관련된주의 (attention) 등과도밀접하게관련된집행주의 (executive attention) 기제로정의되기도하였다. 앞에서살펴본바와같이작업기억에관한조작적정의는다양하게진화되어왔으며연구가들에따라조금씩견해의차이를보이기도한다. 실어증환자들의작업기억및단기기억에관한문헌에따르면, 연구가들마다사용하는조작적정의에차이가있다. Friedmann & Gvion (2003) 의경우, 작업기억과단기기억에관한구분을하지않고, 단기기억측정에바탕을둔숫자및단어바로따라말하기과제를음운작업기억과제로분류하여기억체계분류에혼선을초래하였다. 반면, Tompkins et al. (1994) 의경우, 실어증환자들을위해개정된듣기폭과제 (listening span task) 를통해측정된수행능력을 Just & Carpenter (1992) 의이론을바탕으로한작업기억용량을나타내는지표로정의하였다. 본연구에서는 Tompkins et al. (1994) 과같이 Just & Carpenter (1992) 의작업기억용량이론에바탕을둔정보의유지및조작에필요한인지기제로서작업기억을조작적정의로사용하고자하며, 단기기억은작업기억의하위개념으로서단순히정보를짧은기간동안유지하는데필요한수동적인저장공간 (passive storage buffer) 으로서의정의를차용하고자한다. 또한본연구에서사용되는모든기억기제에관한용어는시공간적도메인과관련된비언어적인기억기제를제외한언어적처리와관련된도메인에국한되어있음을밝혀둔다. 작업기억을평가하는과제에는크게두가지가있다. 하나는이중과제 (dual task) 를사용하는것으로서, 대표적인과제로는 Daneman & Carpenter (1980) 가개발한문장폭읽기과제 (sentence reading span task) 가있다. 이과제에서는피험자가문장을읽은후, 문장의옳고그름을판단한다음각문장의마지막단어를기억했다가몇개의문장읽기과제가끝나면문장의마지막단어들을기억해서말하는 (recall) 286

성지은 / 실어증환자의단기기억및작업기억용량과실어증중증도및문장처리와의상관 과제이다. 이러한문장폭읽기작업기억과제는다양한문장처리과제와의상관관계를보이며작업기억이문장처리에기반이되는인지적기제로서주목을받게되었다. 이외에도 Turner & Engle (1989) 이개발한계산폭과제 (computation/operation span task) 가이중과제를사용한작업기억과제속한다. 또다른작업기억과제의한종류는이중과제가아닌하나의과제 (single task) 에조작적처리과정을첨가한과제이다. 즉, 청각적으로제시되는단어들을알파벳순서로재배열하는과제 (alphabet span task; Craik, 1986) 또는숫자거꾸로따라말하기 (Botwinick & Storandt, 1974), 숫자에서 2를빼서말하기 (subtract-2 span task) (Salthouse, 1988) 등이이에해당한다. 이러한다양한작업기억과제들이하나의인지적요소에기여하는공통적요인이있는지를알아본요인분석 (factor analysis) 결과, 알파벳, 빼기-2, 단어거꾸로말하기, 문장폭과제등은하나의요인으로묶여지며, 이는 66% 의분산을설명하는것으로보고되었다 (Waters & Caplan, 2003). 이러한작업기억과제들은언어장애가있는환자군에적용하기위해변형되어왔다. Tompkins et al. (1994) 은문장폭읽기과제를실어증및우뇌손상환자군에적용하기위해문장길이및마지막재인단어들을보다통제하여읽기대신듣기폭과제로수정하였다. 문장폭듣기과제에서또한실어증환자및우뇌손상환자군의문단읽기과제 (passage comprehension task) 및청각적이해과제와유의한상관관계가보고되었다. 같은작업기억과제는이후, Sung et al. (2009) 논문에서도실어증환자들을대상으로사용되었다. 이연구에서또한문장폭듣기과제는 Computerized Revised Token Test ( 이하 CRTT) (McNeil et al., 2008) 의듣기및읽기과제와 Porch Index of Communicative Ability ( 이하 PICA) (Porch, 2001) 와유의한상관관계를보였다. 하지만, 저자들이지적한바와같이, 문장의마지막단어들을말하는과제는말운동구어장애가동반된실어증환자에게적용하는데어려움이있을뿐만아니라결과해석에도어려움이있다. Caspari et al. (1998) 의경우, 마지막단어를말하도록하는대신에목표단어들을그림으로제시한후, 지시하기 (pointing) 과제로변형된문장폭읽기및듣기작업기억과제를실어증환자들을대상으로실시하였다. 지시하기를통해평가된작업기억과제또한실어증환자를위한읽기이해평가 (Reading Comprehension Battery for Aphasia) 및웨스턴실어증평가의실어증지수 (Western Aphasia Battery Aphasia Quotient) 와유의한상관관계를보였다. 실어증환자들의단기기억및작업기억평가를위해서는정상인들을대상으로개발된검사도구의직접적인적용에어려움이제기되어왔다. 하지만, 말하기과제가아닌지시하기과제를통해실어증환자들의기억기제를평가한논문은앞에서살펴본바와같이매우제한적이다. 따라서본연구에서는가장널리쓰이고있는단기기억과제인단어및숫자바로따라말하기과제를지시하기과제로변형하여실어증환자군에게적용하였다. 또한단어및숫자를거꾸로따라지시하기과제를도입하여거꾸로전환하는조작적요소를첨가한작업기억기제도함께평가하고자하였다. 또한이러한기억과제들이실어증중증도및문장처리능력과의관계를보고한기존의연구와일치되는결과를나타내는지를알아보고자하였다. 본연구의연구문제는다음과같다. 첫째, 단어및숫자의바로따라지시하기및거꾸로따라지시하기과제에따른실어증환자군과정상대조군간에유의한차이가있는가? 둘째, 각각의단기및작업기억과제가공통적인지기제를평가하고있는가? 셋째, 실어증환자군에서각각의단기및작업기억과제와실어증중증도및문장이해과제와유의한상관관계를보이는가? 마지막으로, 실어증환자군에서각각의기억과제중, 실어증중증도및문장이해과제를유의하게예측하는변수는무엇인가? Ⅱ. 연구방법 1. 연구대상본연구에참여한대상은영어를모국어로사용하며, 미국피츠버그에거주하는정상노인 (n = 30) 들과뇌졸중으로인한실어증환자 (n = 20) 이다. 정상노인들의경우, Snellen chart를사용한시력검사, Assessment Battery of Communication in Dementia (ABCD) (Bayles & Tomoeda, 1993) 를통한치매감별검사를통과하였으며, 언어및인지적신경학적손상및발달적병력이보고되지않은노인들을대상으로하였다. 20명의실어증환자들은좌뇌의피질및 287

언어청각장애연구 2010;15;285-297 피질하부위의뇌졸중에기인한언어장애를보이는환자들로서, 실어증중증도평가하기위해 PICA (Porch, 2001) 를사용하였다. PICA의경우, Western Aphasia Battery (Kertesz, 1979) 또는 Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1983) 와같은검사도구와는달리실어증환자를유형에따라구분하지않고전반적인중증도를나타내는총점 (overall score) 및백분위점수로제시된다. 이검사도구는특정양태별로불균등한손상을바탕으로실어증을분류하는학파들과는달리 (e.g., Goodglass & Kaplan, 1983; Kertesz, 1979.), 실어증이란모든양태 (cross-modality) 의손상에기반을두고있다는이론에바탕을둔학파 (e.g., Darley, 1982; McNeil, 1982; Schuell, Jenkins & Jimenez-Pabon, 1964) 에기반을두고있다. 따라서, 본연구에서는후자이론에기반을둔 PICA를통해실어증환자들을평가하였으며, 본연구의실어증에관한조작적정의는 McNeil & Pratt (2001) 에서밝힌언어하위영역및모든양태의전반적손상 (cross-modality overall language impairments) 이론에바탕을두어실어증환자를유형에따라분류하지않았다. 대신, 전반적실어증중증도를 PICA의총점및백분위점수로제시하였다 (< 표 -1>). 실어증환자의평균사후발병기간은 116개월이며표준편차는 127개월이다. 또한실어증환자들의문장이해및처리과정을살펴보기위한과제로 Computerized Revised Token Test-Auditory ( 이하 CRTT-A) (McNeil et al., 2008) 를실시하였다. 이외에도기억과제수행의기반이되는단어수준의이해정도를기술하기위해모든실험참가자를대상으로 Psycholinguistic Assessments of Language Processing in Aphasia ( 이하 PALPA) (Kay, Lesse & Coltheart, 1992) 의하위검사인명사이해과제와함께 The Northwestern Assessment of Verbs and Sentence-Revised ( 이하 NAVS-R) (Thompson, Ballard & Tait, 2008) 의하위검사중동사이해과제를실시하였으며, 비구어적인지능력을평가하는 the Raven Coloured Progressive Matrices ( 이하 RCPM) (Raven, 1965) 또한실시하였다. 두집단의평균연령및평가항목에대한평균점수들은 < 표 -1> 과같다. 연령, 교육수준및사전검사에서유의한집단간차이가있는지살펴보기위해일요인분산분석 (Oneway ANOVA) 을실시하였다. 결과, 연령 (F(1, 49) = 2.76, p >.05), 교육수준 (F(1, 49) = 2.76, p >.05) 및 PALPA (F(1, 49) = 3.28, p >.05) 에서는집단간차이가유의하지않았으나, PICA (F(1, 49) = 59.33, p <.05), CRTT-A (F(1, 49) = 36.24, p <.05), NAVS-R (F(1, 49) = 7.72, p <.05), 및 RCPM (F(1, 49) = 6.98, p <.05) 에서는모두실어증환자군이정상성인에비해낮은점수를보였다. 명사로구성된작업기억및단기기억과제를고려할때, 실어증환자군이명사이해에서정상군과유의한차이를보이지않았다는면에서, 기본적인단어수준에서의의미처리과정에는문제가없는것으로판단되며이는기억과제들에서나타날수있는수행력저하가단어수준에서의처리능력의문제에국한되지않을수있음을밝혀둔다. 2. 실험과제단기기억과제로는 Martin, Kohen & Kalinyak- Fliszar (2008) 에의해실어증환자들을대상으로사용된바있는숫자바로따라지시하기 (Digit Forward: DF, 이하 DF) 및단어바로따라지시하기 (Word Forward: WF, 이하 WF) 과제를사용하였다. 작업기억과제로는 Martin, Kohen & Kalinyak-Fliszar (2008) 과제를거꾸로따라지시하기로변형한과제를각각숫자거꾸로따라지시하기 (Digit Backward: DB, 이하 DB) 와단어거꾸로따라지시하기 (Word Back- < 표 - 1> 실험참가자의연령및사전검사평균 ( 표준편차 ) 연령 a) PICA (OA) b) PICA (%ile) c) CRTT-A d) PALPA e) NAVS-R f) RCPM g) 교육년수 h) 정상성인 66 (12) 14.26 (0.23) 30 i) (18) 14.4 (0.5) 39.37 (0.76) 21.97 (0.18) 32.1 (2.77) 14 (2) 실어증환자 60 (14) 13.03 (0.83) 78 j) (18) 13.01 (1.11) 38.75 (1.62) 21.45 (1) 28.4 (6.91) 16 (3) a) 단위 : 세, PICA(OA): Porch Index of Communicative Ability (Overall Ability), PICA(%ile): Porch Index of Communicative Ability (Percentile), CRTT-A: Computerized Revised Token Test-Auditory, PALPA: Psycholinguistic Assessments of Language Processing in Aphasia, NAVS-R: Northwestern Assessment of Verbs and Sentence-Revised, RCPM: Raven Coloured Progressive Matrices, 단위 : 년, Duffy & Keith (1980) 의자료임, PICA(Porch, 2001) 의자료임. 288

성지은 / 실어증환자의단기기억및작업기억용량과실어증중증도및문장처리와의상관 ward: WB, 이하 WB) 로명명하여사용하였다. Martin, Kohen & Kalinyak-Fliszar (2008) 의과제프로토콜에따르면각숫자폭을다음으로진행하기전에두개의연습문항을제시하도록되어있으며, 연습문항을통해충분히과제에대해숙지할수있도록하였다. 실어증환자군의전반적인언어능력평균은 78%ile로서 mild-to-moderate 해당하여과제수행자체를이해하는데어려움을보이는환자는없는것으로판단되었다. 네가지기억과제들은총 7개의 span (span1 span7) 으로구성되어있으며, 각 span 당 10개의문항으로구성되어있다. 예를들어 span4에서는네개의숫자또는단어를듣게된다. 피험자가한 span에서총 10문항중 6문항이상오답을보이면더이상다음 span으로진행하지않는다. 예를들어, 피험자가 span4에서 10개중 4개의문항을맞출경우, span4 에서멈추게되고이피험자의기억과제폭점수는 3이된다. 하지만, span4에서 10개중 5개문항에서정답을보일경우, 다음 span5로진행하게되고, span5에서 6개의오답을보일경우, 피험자의기억과제폭점수는 4가된다. 단, 이때 5개만오답을보였을경우에는부분점수가부여되어피험자의기억과제폭점수는 4.5가된다. 단간요인이었으며, 기억과제폭 (memory span) 점수가종속변수였다. 집단간주효과가유의하였으며 (F(1, 49) = 50.57, p <.001), 실어증환자들의기억과제폭이유의하게정상대조군에비해낮았다. 단어- 숫자과제주효과또한유의하였으며 (F(1, 49) = 96.87, p <.001), 단어과제에서의기억과제폭이숫자과제에비해유의하게낮았다. 바로-거꾸로따라지시하기에관한주효과또한유의하였으며 (F(1, 49) = 225.66, p <.001), 거꾸로따라지시하기과제에서바로따라지시하기에비해유의하게기억과제폭이낮은것으로나타났다. 집단 단어-숫자 바로-거꾸로따라지시하기간의삼원상호작용이유의하였다 (F(1, 49) = 50.57, p <.001). 유의한삼원상호작용결과를바탕으로, LMATRIX 및 MMATRIX syntax를이용하여상호작용대비 (interaction contrast) 를통해사후검정을실시하였다. 그결과, 삼원상호작용이나타난지점은숫자거꾸로따라지시하기에서의집단간차이가단어거꾸로따라지시하기에서의집단간차이에비해유의하게크기때문인것으로나타났다 (p <.05). 각조건별집단간기억과제폭에관한정보는 < 그림 -1> 에제시되었다. 3. 연구절차및자료분석 E-PRIME 1.0 소프트웨어를사용하여제작된모든자극들은컴퓨터로제시되었다. 청각적자극은 60dB 로제시되었으며, 지시하는보기들은 9개의숫자또는그림이있는화면으로구성되어터치스크린에제시되었다. 조용한방에서개별적으로자료를수집하였으며각기억과제시작이전에 2개의연습문항이제시되었다. SPSS 17.0 for Windows 프로그램을사용하여통계분석을실시하였다. Ⅲ. 연구결과 1. 혼합삼요인분산분석 (Mixed three-way ANOVA) 첫번째연구문제인, 기억과제에따른집단간차이를알아보기위해삼요인분산분석을실시하였다. 단어-숫자과제요인및바로-거꾸로따라지시하기과제요인이집단내요인이며, 실어증환자군-대조군이집 < 그림 - 1> 집단간단어및숫자바로따라지시하기및거꾸로따라지시하기과제점수 2. 주성분분석 (Principal Component Analysis) 두번째연구질문은 4가지기억과제가공통적인인지기제를평가하고있는지를알아보는것이다. 이를위해각집단별로주성분분석을실시하였다. 결과, 정상인과실어증환자군모두에서 4개의기억과제가한가지공통적인성분으로묶여지는것으로나타났다. 한가지로추출된주성분이정상인의경우총분산 289

언어청각장애연구 2010;15;285-297 의 78%, 실어증환자의경우총분산의 79% 의설명력을보였다. 3. 상관관계분석 세번째연구문제인기억과제와실어증중증도 (PICA) 및문장처리검사 (CRTT-A) 간의상관관계를살펴보기위해실어증환자들을대상으로 Pearson 상관계수를산출하였다. PICA의경우, 4가지기억과제와모두유의한상관관계를보였으며그범위는.48.78이었다. 이와는대조적으로 CRTT-A의경우, 숫자및단어바로따라지시하기과제와는유의한상관관계를보였으나작업기억과제인거꾸로따라지시하기과제와의상관계수는통계적으로유의하지않았다. 상관계수는 < 표 -2> 에제시하였으며, PICA와기억과제들의산점도 (scatterplot) 는 < 그림 -2> 에 CRTT-A와기억과제들의산점도는 < 그림 -3> 에지시하였다. < 표 - 2> 기억과제와실어증중증도및문장처리관제간의피어슨상관계수 DF a) WF b) DB c) WB d) PICA e).78 **.67 **.52 *.48 * CRTT-A f).57 **.46 *.05.15 a) DF: Digit Forward, 숫자바로따라지시하기, b) WF: Word Forward, 단어바로따라지시하기, c) DB: Digit Backward, 숫자거꾸로따라지시하기, d) WB: Word Backward, 단어거꾸로따라지시하기, e) PICA: Porch Index of Communicative Ability, f) CRTT-A: Computerized Revised Token Test- Auditory < 그림 - 2> Porch Index of Communicative Ability와기억과제간의산점도 < 그림 - 3> Computerized Revised Token Test-Auditory와기억과제간의산점도 4. 다중회귀분석마지막연구문제로서, 네가지기억과제중실어증환자의중증도와문장처리과제를가장잘예측하는기억과제를찾기위해단계적다중선형회귀분석 (stepwise multiple linear regression analysis) 을실시하였다. PICA (F(1, 18) = 28.19, R 2 =.61, p <.001) 및 CRTT-A (F(1, 18) = 8.33, R 2 =.32, p <.05) 모두유의하게예측한변수는 DF, 즉숫자바로따라지시하기과제였다. Ⅳ. 논의및결론 실어증중증도및실어증환자들의언어처리과정에기반이되는인지적요소에대한관심이부각되고있다. 이중에서도단어들의연속으로구성되는문장처리영역의경우, 일시적으로정보가제시되었다가사라진다는점, 단어들을조합하여문장구조에따라재해석해야한다는점등으로인해다른다양한인지적기제중에서도특히기억기제와의관련성에대한연구가다양화되고있다. 하지만, 심리학자들이정상인평가를위해개발한기억검사도구들의경우, 실어증환자들에게직접적으로적용하는데서론에서도언급한바와같이다양한문제점이존재한다. 따라서본연구에서는단기및작업기억과제를지시하기과제로변형하여단어및숫자의양태별실어증환자의수행능력을정상노인들과비교하였으며, 실어증중증도및문장처리능력을가장잘예측하는기억과제가무엇인지알아보고자하였다. 기존의작업기억이론들을바탕으로, 바로따라지시하기과제는단기기억을평가하는과제로거꾸로따라지시하기과제는 290

성지은 / 실어증환자의단기기억및작업기억용량과실어증중증도및문장처리와의상관 작업기억을평가하는지표로삼았다. 실어증환자군은정상노인에비해네가지기억과제모두에서낮은수행력을보였다. 또한거꾸로따라지시하기과제가바로따라지시하기에비해더어려운것으로나타났으며, 두집단모두숫자보다단어에서더어려움을보였다. 혼합삼원분산분석에서나타난삼원상호작용분석결과에따르면, 거꾸로따라지시하기과제에서숫자를사용한자극에서두집단간차이가가장크게나타났으며, 이차이는단어거꾸로따라지시하기에서의집단간차이에비해유의하게큰것으로나타났다. 반면, 바로따라지시하기과제에서의집단간차이는단어또는숫자양상에따라유의한차이가나타나지않았다. 다시말해, 실어증환자들은네가지기억과제에서공통적으로정상인들에비해낮은수행력을보였지만, 실어증환자군과정상노인군간의수행력차이가비균등하게 (disportionate) 낮아지는과제는숫자거꾸로따라지시하기였다. 이러한결과는부분적으로작업기억용량이론 (working memory capacity theory) 에서설명하는현상과일치한다. 작업기억용량이론에따르면, 작업기억용량이낮은집단의경우과제의난이도가높아질수록작업기억용량이높은집단에비해비균등한수행력저하 (disportionate decrease of performance) 를보인다고설명한다 (Just & Carpenter, 1992; Miyake, Carpenter & Just, 1994). 본연구에서는작업기억용량이낮은실어증환자군이정상인에비해난이도가높은거꾸로따라지시하기과제에서유의한집단간차이를보였다는면에서작업기억용량이론과일치하지만, 거꾸로따라지시하기과제내에서는오히려난이도가높은단어가아닌비교적쉬운숫자에서더큰집단간차이를보인결과는작업기억용량이론이예측하는결과와일치하지않는다. 이는정상대조군이노인층이었다는측면에서, 노령화에의한인지적기능감퇴에따라인지적부담 (cognitive load) 이가장큰단어거꾸로따라지시하기과제에서정상노인들의수행력이저하되어다른과제에비해상대적으로실어증환자군과의수행력차이가감소한것에기인하는것으로해석된다. 이는노령화에따른작업기억용량감소에관한기존연구들과일치하는결과이다 (Morris, Gick & Craik, 1988; Waters & Caplan, 2001; 2005). 분산분석결과에따르면작업기억과제 ( 거꾸로따라지시하기 ) 가단기기억과제 ( 바로따라지시하기 ) 에 비해어려운것으로나타났지만, 주성분분석결과에따르면네가지단기및작업기억과제들은하나의성분으로설명될수있는것으로나타났다. 공통된하나의성분을개념화하자면, 단기간정보를저장하거나조작하는데필요한인지적기제로설명할수있을것이다. 기억과제들과실어증중증도를평가하는 PICA 점수와는대체로높은상관관계를보였으나, 문장처리과정을평가한 CRTT-A와는단기기억과제인바로따라지시하기과제에서만유의한상관관계를보였다. 이는문장듣기폭기억과제를사용하여평가한실어증환자군의작업기억용량이 PICA를비롯해 CRTT-A와도유의한상관관계를보였다는기존의보고 (Sung et al., 2009) 와일치하지않는결과이다. 즉, 숫자및단어거꾸로따라지시하기과제를통해측정한실어증환자군의작업기억용량은실어증중증도와는관련이있지만, 문장처리과제와의관계를예측하는데는민감하지않은과제일수있음을시사한다. 이는다중회귀분석에서나타는결과로도설명되는데, PICA와 CRTT-A 에서의수행력을공통적으로예측한변수는단기기억과제인숫자바로따라지시하기과제였다. 이러한결과는정상성인을대상으로한기존의연구결과및이론과도상반된다. 서론에서언급한 Engle, Kane 및동료들의연구결과에따르면, 단기기억과제가아닌작업기억과제에서상위인지기제 (higherorder cognitive mechanism) 를측정하는과제들과높은상관관계를보이는것으로나타났으나, 본연구에서는단기기억과제중에서도가장난이도가낮은숫자바로따라지시하기과제가실어증환자의중증도및문장처리과정을예측하는변수로나타났다. 이러한결과는기존의작업기억이론으로설명되기는힘들지만, 기억과제자체의특징과실어증환자들의인지적부하량에따른수행력을좀더자세하게살펴보는것으로설명될수있다. 즉, 산점도에서나타나듯, 난이도가낮은숫자바로따라지시하기과제의경우기억폭이 3.0에서 7.0까지점수폭의범위가비교적넓었으나, 난이도가가장어려운단어거꾸로따라지시하기과제의경우기억폭이 2.0 4.6으로서매우제한적이다. 이러한제한적인점수분포는통계적으로상관관계를떨어뜨리고또한상관관계를바탕으로하는회귀분석결과에도영향을줄수있다. 이렇게과제의난이도에따라점수폭이달라지고변수들의분포가달라지는이유로는, 인지적부하량이높은기억과 291

언어청각장애연구 2010;15;285-297 제에서는실어증환자군의수행력이하향평준화되었기때문임을추론할수있다. 즉, 개인의기억용량을넘어서는과제의경우, 집단의다양성 (variability) 을감소시켜상관관계가낮아지며예측변수에도영향을줄수있음을알수있다. 따라서작업기억및단기기억과제의선정에있어, 실어증환자들의언어손상중증도와관련된인지적기제손상에관해연구하기위해서는, 개인차를가장잘재현할수있는적절한난이도에관한선정이중요함을알수있다. 본연구에따르면, 실어증환자군의중증도및문장처리과제와관련된기억기제를나타내는지표로는거꾸로따라지시하기과제보다는바로따라지시하기, 또한의미적처리과정 (semantic processing) 이포함된단어보다는숫자가손상에대한개인차를더욱잘대변하는과제임을시사한다. 이는언어임상가및연구가로서실어증환자의언어손상과관련된기억기제를평가할때, 다양한과제중가장언어적손상과관련있는과제를단시간에평가할수있는과제를제시하였다는점에서임상적시사점이있다고하겠다. 이는기존의실어증중증도및기억과제수행능력비교연구에서는살펴보지않은것으로, 임상에서문장폭과제와같은복잡한작업기억과제 (complex working memory tasks) 대신, 단기기억에바탕을둔숫자바로따라지시하기과제를통해환자의언어- 기억 (verbal memory) 손상정도를살펴볼수있다면, 더욱효율적인평가가될수있을것이다. 본연구의제한점으로는한국임상현실에직접적으로적용할수있는검사도구를사용하지않았다는점과더불어, 단어및숫자를활용한기억과제이외에이중과제 (dual task) 를사용한보다복잡한작업기억과제 (complex working memory task) 와같은다양화된기억과제사용의부재이다. 다양한기억과제들의비교를통해가장실어증중증도와관련이있는기억과제를살펴보는것이필요할것이다. 또한 PICA 및 CRTT-A 외에다양한평가도구를사용하여실어증환자들의언어손상과기억기제와의관련성을연구하는것이필요하겠다. 실어증중중도와언어처리과정에영향을주는인지적기제에관한연구는실어증환자들이보이는언어증상의보다근본적인기제 (underlying mechanism) 에관한평가를바탕으로다양화된실어증치료접근방법고안에도도움을줄수있을것으로기대된다. 참고문헌 Baddeley, A. D. (2000). Short-term and working memory. In E. Tulving & F. I. M. Craik (Eds.), The Oxford handbook of memory (pp. 77-92). New York, NY: Oxford University Press. Baddeley, A. D., & Hitch, G. (1974). Working memory. In G. A. Bower (Ed.), Recent advances in learning and motivation (Vol. 8) (pp. 47-90). New York, NY: Academic Press. Baddeley, A. D. (1986). Working memory. New York, NY: Oxford University Press. Bayles, K., & Tomoeda, C. (1993). Arizona Battery for Communication Disorders of Dementia. Tucson, AZ: Canyonlands Publishing. Botwinick, J., & Storandt, M. (1974). Memory, related functions and age. Springfield, IL: Thomas. Caplan, D., & Waters, G. (1995). Aphasic disturbances of syntactic comprehension and working memory capacity. Cognitive Neuropsychology, 12, 637-649. Caspari, I., Parkinson, S. R., LaPointe, L. L., & Katz, R. C. (1998). Working Memory and Aphasia. Brain and Cognition, 37, 205-223. Cattell, R. N. (1973). Measuring intelligence with the Culture Fair tests. Champaign, IL: Institute for Personality and Ability Testing. Cowan, N. (1988). Evolving conceptions of memory storage, selective attention, and their mutual constraints within the human information processing system. Psychological Bulletin, 104, 163-191. Cowan, N. (1995). Attention and memory: An integrated framework. Oxford: Oxford University Press. Craik, F. I. M. (1986). A functional account of age differences in memory. In F. Klix & H. Hagendorf (Eds.), Human memory and cognitive capabilities (pp. 409-422). Amsterdam: North-Holland. Daneman, M., & Carpenter, P. A. (1980). Individual differences in working memory and reading. Journal of Verbal Learning and Verbal Behavior, 19, 450-466. Darley, F. L. (1982). Aphasia. Philadelphia, PA: W. B. Saunders. Engle, R. W., & Kane, M. J. (2004). Executive attention, working memory capacity, and a two-factor theory of cognitive control. In B. Ross (Ed.), The psychology of learning and motivation (pp. 145-199). New York: Academic Press. 292

성지은 / 실어증환자의단기기억및작업기억용량과실어증중증도및문장처리와의상관 Engle, R. W. (2001). What is working memory capacity? In H. L. Roediger III, J. S. Nairne, I. Neath & A. M. Surprenant (Eds.), The nature of remembering: Essays in honor of Robert G. Crowder (pp. 297-314). Washington, DC: American Psychological Association. Engle, R. W. (2002). Working memory capacity as executive attention. Current Directions in Psychological Science, 19-23. Engle, R. W., Tuholski, S. W., Laughlin, J. E., & Conway, A. R. A. (1999). Working memory, short-term memory, and general fluid intelligence: A latentvariable approach. Journal of Experimental Psychology: General, 128, 309-331. Friedmann, N., & Gvion A. (2003). Sentence comprehension and working memory limitation in aphasia: A dissociation between semantic-syntactic and phonological reactivation. Brain and Language, 86, 23-39. Goodglass, H., & Kaplan, E. (1983). The assessment of aphasia and related disorders (2nd ed.). Philadelphia, PA: Lea & Febiger. Ivanova, M., & Hallowell, B. (2010). An eye-tracking method to investigate working memory in individuals with and without aphasia. Proceedings of the Clinical Aphasiology annual conference. Isle of Palms, SC. Just, M. A., & Carpenter, P. A. (1992). A capacity theory of comprehension: Individual differences in working memory. Psychological Review, 99, 122-149. Kane, M. J., & Engle, R. W. (2000). Working-memory capacity, proactive interference, and divided attention: Limits on long-term memory retrieval. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 336-358. Kane, M. J., & Engle, R. W. (2003). Working-memory capacity and the control of attention: The contributions of goal neglect, response competition, and task set to stroop interference. Journal of Experimental Psychology: General, 132, 47-70. Kane, M. J., Poole, B. J., & Tuholski, S. W., & Engle, R. W. (2006). Working memory capacity and the top-down control of visual search: Exploring the boundaries of executive attention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 32, 749-777. Kay, J., Lesser, R., & Coltheart, M. (1992). PALPA: Psycholinguistic Assessments of Language Processing in Aphasia. England: Lawrence Erlbaum Associates. Kertesz, A. (1979). Aphasia and associated disorders: Taxonomy, localization and recovery. New York, NY: Grune & Stratton. Martin, N., Kohen, F., & Kalinyak-Fliszar, M. (2008). A diagnostic battery to assess language and short-term memory deficits in aphasia. Proceedings of the Clinical Aphasiology annual conference. Teton Village, WY. McNeil, M. R. (1982). The nature of aphasia in adults. In N. J. Lass, L. McReynolds, J. Northern, & D. Yoder (Eds.), Speech, language, and hearing (Vol. II). Philadelphia, PA: Saunders. McNeil, M. R., & Pratt, S. R. (2001). Defining aphasia: Some theoretical and clinical implications of operating from a formal definition. Aphasiology, 15, 901-911. McNeil, M. R., Sung, J. E., Pratt, S. R., Szunimsky, N., Kim, A., Ventura, M., & Doyle, P. (2008). Concurrent validation of the Computerized Revised Token Test (CRTT) and three experimental reading CRTT- R versions in normal elderly individuals and persons with aphasia. Proceedings of the Clinical Aphasiology annual conference. Teton Village, WY. Miyake, A., Carpenter, P. A., & Just, M. S. (1994). Acapacity approach to syntactic comprehension disorders: Making normal adults perform like aphasic patients. Cognitive Neuropsychology, 11, 671-717. Morris, R. G., Gick, M. L., & Craik, F. I. M. (1988). Processing resources and age differences in working memory. Memory and Cognition, 16, 362-366. Porch, B. E. (2001). The Porch Index of Communicative Ability (3rd ed.). Palo Alto, CA: Consulting Psychologists Press. Raven, J. C., Court, J. H., & Raven, J. (1977). Raven s Progressive Matrices and Vocabulary Scales. New York, NY: Psychological Corporation. Raven, J. C. (1965). The Coloured Progressive Matrices. New York, NY: The Psychological Corporation. Salthouse, T. A. (1988). Resource-reduction interpretations of cognitive aging. Developmental Review, 8, 238-272. Schuell, H., Jenkins, J. J., & Jimenez-Pabon, E. (1964). Aphasia in adults: Diagnosis, prognosis and treatment. New York, NY: Hoeber Meducal Division, Harper & Row Publishers. Sung, J. E., McNeil, M. R., Pratt, S. R., Dickey, M. W., Hula, W. D., Szuminsky, N., & Doyle, P. J. (2009). Verbal working memory and its relationship to 293

언어청각장애연구 2010;15;285-297 sentence-level reading and listening comprehension in persons with aphasia. Aphasiology, 23, 1040-1052. Thompson, C. K., Ballard, K., & Tait, M. E. (2008). Northwestern Assessment of Verbs and Sentences-Revised (NAVS-R). [Unpublished raw data], Northwestern University. Tompkins, C. A., Bloise, C. G. R., Timko, M. L., & Baumgaertner, A. (1994). Working memory and inference revision in brain-damaged and normally aging adults. Journal of Speech and Hearing Research, 37, 896-912. Turner, M. L., & Engle, R. W. (1989). Is working memory capacity task dependent? Journal of Memory and Language, 28, 127-154. Waters, G. S., & Caplan, D. (2001). Age, working memory, and on-line syntactic processing in sentence comprehension. Psychology and Aging, 16, 128-144. Waters, G. S., & Caplan, D. (2003). The reliability and stability of verbal working memory measures. Behavior Research Methods, Instruments, and Computers, 35, 550-564. Waters, G. S., & Caplan, D. (2005). The relationship between age, processing speed, working memory capacity, and language comprehension. Memory, 13, 403-413. 294

Sung / Performances on Short-Term and Working Memory Tasks and Their Relationships to Aphasia Severity and Auditory Comprehension in Normal Elderly Adults and People with Aphasia ABSTRACT Performances on Short-Term and Working Memory Tasks and Their Relationships to Aphasia Severity and Auditory Comprehension in Normal Elderly Adults and People with Aphasia Jee Eun Sung Department of Communication Disorders, Ewha Womans University, Seoul, Korea Correspondence to Prof. Jee Eun Sung, PhD, Department of Communication Disorders, Ewha Womans University, 11-1 Daehyun-dong, Seodaemoon-gu, Seoul, Korea e-mail: jeesung@ewha.ac.kr tel.: + 82 2 3277-2208 Background & Objectives: Short-term memory and working memory capacities have gained considerable attention as underlying cognitive mechanisms, which may account for language processing difficulties in people with aphasia. However, there are limitations to the employment of short-term and working memory tasks for assessing normal cognitive processing in order to evaluate language-impaired clinical populations. The current study investigated 1) the performance differences between people with aphasia and normal elderly adults in short-term memory and working memory tasks when the stimuli modality was manipulated using digits and words and 2) how their performances on the memory tasks were related to aphasia severity and sentence processing. Methods: Twenty people with aphasia and 30 normal elderly adults participated in the present study. Digit forward and word forward span tasks served as short-term memory tasks, and digit backward and word backward span tasks served as working memory tasks. Porch Index of Communicative Ability (PICA) was used as a measure of language impairment severity, and the Computerized Revised Token Test (CRTT) was a measure of sentence processing. Results: Both groups showed greater difficulties in working memory tasks than short-term memory tasks and those involving words compared to those involving digits. The greatest group differences were found in the digit backward span task. Principal component analysis of four span tasks revealed that a one-factor solution accounted for approximately 80% of the total variance in both groups, indicating that the four span measures served as a unified index of the underlying memory-related cognitive mechanism that is responsible for maintaining and manipulating information. Among the four span measures, the digit forward task significantly predicted aphasia severity and sentence-processing abilities in people with aphasia. Discussion & Conclusion: Results were partially consistent with the working memory capacity theory. Korean versions of short-term and/or working memory span tasks need to be developed in order to investigate the underlying cognitive mechanisms responsible for language impairments in aphasia. (Korean Journal of Communication Disorders 2010;15;285-297) Key Words: short-term memory, working memory, pointing span tasks, aphasia severity, sentence processing REFERENCES Baddeley, A. D. (2000). Short-term and working memory. In E. Tulving & F. I. M. Craik (Eds.), The Oxford handbook of memory (pp. 77-92). New York, NY: Oxford University Press. Baddeley, A. D., & Hitch, G. (1974). Working memory. In G. A. Bower (Ed.), Recent advances in learning Received, July 20, 2010 Final revision received, August 30, 2010 Accepted, September, 5, 2010. c 2010 The Korean Academy of Speech-Language Pathology and Audiology http://www.kasa1986.or.kr 295

Korean Journal of Communication Disorders 2010;15;285-297 and motivation (Vol. 8) ) (pp. 47-90). New York, NY: Academic Press. Baddeley, A. D. (1986). Working memory. New York, NY: Oxford University Press. Bayles, K., & Tomoeda, C. (1993). Arizona Battery for Communication Disorders of Dementia. Tucson, AZ: Canyonlands Publishing. Botwinick, J., & Storandt, M. (1974). Memory, related functions and age. Springfield, IL: Thomas. Caplan, D., & Waters, G. (1995). Aphasic disturbances of syntactic comprehension and working memory capacity. Cognitive Neuropsychology, 12, 637-649. Caspari, I., Parkinson, S. R., LaPointe, L. L., & Katz, R. C. (1998). Working Memory and Aphasia. Brain and Cognition, 37, 205-223. Cattell, R. N. (1973). Measuring intelligence with the Culture Fair tests. Champaign, IL: Institute for Personality and Ability Testing. Cowan, N. (1988). Evolving conceptions of memory storage, selective attention, and their mutual constraints within the human information processing system. Psychological Bulletin, 104, 163-191. Cowan, N. (1995). Attention and memory: An integrated framework. Oxford: Oxford University Press. Craik, F. I. M. (1986). A functional account of age differences in memory. In F. Klix & H. Hagendorf (Eds.), Human memory and cognitive capabilities (pp. 409-422). Amsterdam: North-Holland. Daneman, M., & Carpenter, P. A. (1980). Individual differences in working memory and reading. Journal of Verbal Learning and Verbal Behavior, 19, 450-466. Darley, F. L. (1982). Aphasia. Philadelphia, PA: W. B. Saunders. Engle, R. W., & Kane, M. J. (2004). Executive attention, working memory capacity, and a two-factor theory of cognitive control. In B. Ross (Ed.), The psychology of learning and motivation (pp. 145-199). New York: Academic Press. Engle, R. W. (2001). What is working memory capacity? In H. L. Roediger III, J. S. Nairne, I. Neath & A. M. Surprenant (Eds.), The nature of remembering: Essays in honor of Robert G. Crowder (pp. 297-314). Washington, DC: American Psychological Association. Engle, R. W. (2002). Working memory capacity as executive attention. Current Directions in Psychological Science, 19-23. Engle, R. W., Tuholski, S. W., Laughlin, J. E., & Conway, A. R. A. (1999). Working memory, short-term memory, and general fluid intelligence: A latentvariable approach. Journal of Experimental Psychology: General, 128, 309-331. Friedmann, N., & Gvion A. (2003). Sentence comprehension and working memory limitation in aphasia: A dissociation between semantic-syntactic and phonological reactivation. Brain and Language, 86, 23-39. Goodglass, H., & Kaplan, E. (1983). The assessment of aphasia and related disorders (2nd ed.). Philadelphia, PA: Lea & Febiger. Ivanova, M., & Hallowell, B. (2010). An eye-tracking method to investigate working memory in individuals with and without aphasia. Proceedings of the Clinical Aphasiology annual conference. Isle of Palms, SC. Just, M. A., & Carpenter, P. A. (1992). A capacity theory of comprehension: Individual differences in working memory. Psychological Review, 99, 122-149. Kane, M. J., & Engle, R. W. (2000). Working-memory capacity, proactive interference, and divided attention: Limits on long-term memory retrieval. Journal of Experimental Psychology: Learning, Memory, and Cognition, 26, 336-358. Kane, M. J., & Engle, R. W. (2003). Working-memory capacity and the control of attention: The contributions of goal neglect, response competition, and task set to stroop interference. Journal of Experimental Psychology: General, 132, 47-70. Kane, M. J., Poole, B. J., & Tuholski, S. W., & Engle, R. W. (2006). Working memory capacity and the top-down control of visual search: Exploring the boundaries of executive attention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 32, 749-777. Kay, J., Lesser, R., & Coltheart, M. (1992). PALPA: Psycholinguistic Assessments of Language Processing in Aphasia. England: Lawrence Erlbaum Associates. Kertesz, A. (1979). Aphasia and associated disorders: Taxonomy, localization and recovery. New York, NY: Grune & Stratton. Martin, N., Kohen, F., & Kalinyak-Fliszar, M. (2008). A diagnostic battery to assess language and short-term memory deficits in aphasia. Proceedings of the Clinical Aphasiology annual conference. Teton Village, WY. 296

Sung / Performances on Short-Term and Working Memory Tasks and Their Relationships to Aphasia Severity and Auditory Comprehension in Normal Elderly Adults and People with Aphasia McNeil, M. R. (1982). The nature of aphasia in adults. In N. J. Lass, L. McReynolds, J. Northern, & D. Yoder (Eds.), Speech, language, and hearing (Vol. II). Philadelphia, PA: Saunders. McNeil, M. R., & Pratt, S. R. (2001). Defining aphasia: Some theoretical and clinical implications of operating from a formal definition. Aphasiology, 15, 901-911. McNeil, M. R., Sung, J. E., Pratt, S. R., Szunimsky, N., Kim, A., Ventura, M., & Doyle, P. (2008). Concurrent validation of the Computerized Revised Token Test (CRTT) and three experimental reading CRTT- R versions in normal elderly individuals and persons with aphasia. Proceedings of the Clinical Aphasiology annual conference. Teton Village, WY. Miyake, A., Carpenter, P. A., & Just, M. S. (1994). Acapacity approach to syntactic comprehension disorders: Making normal adults perform like aphasic patients. Cognitive Neuropsychology, 11, 671-717. Morris, R. G., Gick, M. L., & Craik, F. I. M. (1988). Processing resources and age differences in working memory. Memory and Cognition, 16, 362-366. Porch, B. E. (2001). The Porch Index of Communicative Ability (3rd ed.). Palo Alto, CA: Consulting Psychologists Press. Raven, J. C., Court, J. H., & Raven, J. (1977). Raven s Progressive Matrices and Vocabulary Scales. New York, NY: Psychological Corporation. Raven, J. C. (1965). The Coloured Progressive Matrices. New York, NY: The Psychological Corporation. Salthouse, T. A. (1988). Resource-reduction interpretations of cognitive aging. Developmental Review, 8, 238-272. Schuell, H., Jenkins, J. J., & Jimenez-Pabon, E. (1964). Aphasia in adults: Diagnosis, prognosis and treatment. New York, NY: Hoeber Meducal Division, Harper & Row Publishers. Sung, J. E., McNeil, M. R., Pratt, S. R., Dickey, M. W., Hula, W. D., Szuminsky, N., & Doyle, P. J. (2009). Verbal working memory and its relationship to sentence-level reading and listening comprehension in persons with aphasia. Aphasiology, 23, 1040-1052. Thompson, C. K., Ballard, K., & Tait, M. E. (2008). Northwestern Assessment of Verbs and Sentences-Revised (NAVS-R). [Unpublished raw data], Northwestern University. Tompkins, C. A., Bloise, C. G. R., Timko, M. L., & Baumgaertner, A. (1994). Working memory and inference revision in brain-damaged and normally aging adults. Journal of Speech and Hearing Research, 37, 896-912. Turner, M. L., & Engle, R. W. (1989). Is working memory capacity task dependent? Journal of Memory and Language, 28, 127-154. Waters, G. S., & Caplan, D. (2001). Age, working memory, and on-line syntactic processing in sentence comprehension. Psychology and Aging, 16, 128-144. Waters, G. S., & Caplan, D. (2003). The reliability and stability of verbal working memory measures. Behavior Research Methods, Instruments, and Computers, 35, 550-564. Waters, G. S., & Caplan, D. (2005). The relationship between age, processing speed, working memory capacity, and language comprehension. Memory, 13, 403-413. 297