Jee Eun Sung

Verbal working memory and its relationship to sentence‐level reading and listening comprehension in persons with aphasia

Background: Working memory (WM) has gained recent attention as a cognitive construct that may account for language comprehension deficits in persons with aphasia (PWA) (Caspari, Parkinson, LaPointe, & Katz, 1998; Martin, Kohen, & Kalinyak‐Fliszar, 2008; Wright, Downey, Gravier, Love, & Shapiro, 2007). However, few studies have investigated individual differences in performance on sentence comprehension tasks as a function of WM capacity in PWA when WM demands are manipulated. Aims: The purposes of the current study were: (1) to examine the relationships among verbal WM, sentence comprehension, and severity of impairment in PWA and (2) to investigate the differential performance of high versus low verbal WM groups on sentence comprehension tasks in which task demands were manipulated by the length of the sentence stimuli, complexity of syntactic structure, and by presentation method which varied the time over which the linguistic material was available for computation. Methods & Procedures: A total of 20 PWA were divided into high and low WM groups based on a listening version of a WM sentence span task. Each participant completed a listening version (CRTT) and three reading versions (CRTT‐R) of the Computerised Revised Token Test as the sentence comprehension tasks. Outcomes & Results: The WM task significantly predicted performance on the CRTT conditions in which information was only temporarily available, thereby imposing greater WM demands on sentence comprehension. The verbal WM task was significantly correlated with aphasia severity and a principal components analysis revealed that the WM task, overall aphasia severity, and overall reading impairment level loaded on a single factor with 76% of shared variance. The low WM groups performance was significantly lower than the high WM group on the CRTT subtests with syntactically more complex structures and on the CRTT conditions with temporally restricted presentation methods. Conclusions: This verbal WM task was significantly and moderately correlated with the overall severity of aphasia as well as with both listening and reading sentence comprehension. The WM group differences emerged only in sentence comprehension tasks with greater WM demands. These results are consistent with the notion that WM effects are most evident when WM capacity is sufficiently taxed by the task demands (e.g., Caplan & Waters, 1999; Just & Carpenter, 1992).

Comparing connected language elicitation procedures in persons with aphasia: Concurrent validation of the Story Retell Procedure

Background: The Story Retell Procedure (SRP) (Doyle et al., 1998) is a well‐described method for eliciting connected language samples in persons with aphasia (PWA). However, the stimuli and task demands of the SRP are fundamentally different from commonly employed picture description, narrative, and procedural description tasks reported in the aphasia literature. As such, the extent to which measures of linguistic performance derived from the SRP may be associated with those obtained from picture description, narrative, and procedural description tasks is unknown. This research was supported by VA Rehabilitation Research and Development Merit Review Project C3159R “Cognitive and linguistic mechanisms of language performance in aphasia” and the Geriatric Research, Education, and Clinical Center of the VA Pittsburgh Healthcare System. The authors gratefully acknowledge the generous participation of the volunteers for this study and the laboratory assistance of Jennifer Golovin and MaryBeth Ventura. Aims: To assess the concurrent validity of linguistic performance measures obtained from the SRP with those obtained from picture description, narrative, and procedural description tasks by examining the correlations and the magnitude differences across the linguistic variables among the elicitation tasks. Secondarily, we examined the relationship of the percentage of information units per minute (%IU/Min) to other linguistic variables within the SRP and across the other elicitation tasks. Methods and Procedures: This study compared the SRP to six different, frequently used sampling procedures (three sets of picture descriptions, one fairytale generation, one set of narratives, and one set of procedural description tasks) from which the same five verbal productivity, four information content, two grammatical, and two verbal disruption measures were computed. Language samples were elicited from 20 PWA, spanning the aphasia comprehension severity range. Tests of association and difference were calculated for each measure between the SRP and the other sampling methods. Outcomes & Results: Significant and strong associations were obtained between the SRP and the other elicitation tasks for most linguistic measures. The SRP produced either no significant or significantly greater instances of the dependent variable except for the type–token ratio, which yielded a significantly lower value than the other sampling procedures. Conclusions: The findings are interpreted as support for the concurrent validity of the SRP and as evidence that a single form of the SRP will yield a language sample that is generally equivalent in distribution to other sampling procedures, and one that is generally greater in quantity to those typically used to assess connected spoken language in PWA. Additionally, it was found that the %IU/Min metric predicted highly the information content linguistic measures on the SRP as well as on the other elicitation procedures. However, it did not predict well measures of verbal productivity, grammaticality, or verbal disruptions.

Reliability and Validity of the Computerized Revised Token Test: Comparison of Reading and Listening Versions in Persons With and Without Aphasia

PURPOSE This study assessed the reliability and validity of intermodality associations and differences in persons with aphasia (PWA) and healthy controls (HC) on a computerized listening and 3 reading versions of the Revised Token Test (RTT; McNeil & Prescott, 1978). METHOD Thirty PWA and 30 HC completed the test versions, including a complete replication. Reading versions varied according to stimulus presentation method: (a) full-sentence presentation, (b) self-paced word-by-word full-sentence construction, and (c) self-paced word-by-word presentation with each word removed with the onset of the next word. Participants also received tests of aphasia and reading severity. RESULTS The listening version produced higher overall mean scores than each of the reading versions. Differences were small and within 1 standard error of measurement of each version. Overall score test-retest reliability among versions for PWA ranged from r=.89 to r=.97. Correlations between the listening and reading versions ranged from r=.79 to r=.85. All versions correlated highly with aphasia and reading severity. Correlations were generally low for the HC due to restricted variability. Factor analysis yielded a 2-factor solution for PWA and a single-factor for HC. CONCLUSIONS Intermodality differences were small, and all 4 versions were reliable, concurrently valid, and sensitive to similar linguistic processing difficulties in PWA.

Real-time Processing in Reading Sentence Comprehension for Normal Adult Individuals and Persons with Aphasia

Background: Persons with aphasia (PWA) have shown difficulties in integrating linguistic materials over time and distance in sentence processing. However, few studies have investigated sentence-processing difficulties among PWA as reflected in online processing measures. Furthermore, relatively few studies have examined the online processing of syntactically simple but computationally demanding sentences among PWA. Such sentences are important from the perspective of resource-related theories of aphasic language deficits, which predict that such sentences should be challenging for PWA even if the syntactic structures involved are not. Aims: The purpose of the study was to investigate the sentence-level online reading times of normal adult individuals (NAI) and PWA by word category and as a function of adjective padding. It was assumed that head nouns entail greater processing costs than determiners because they represent the point at which integration of material within a noun phrase must take place. It was also assumed that increasing adjectival padding within a noun phrase requires more integration and creates greater processing costs. Methods & Procedures: A total of 30 NAI and 30 PWA participated in the current study. Sentence stimuli were obtained from the Computerised Revised Token Test (CRTT) (McNeil et al., 2008). Sentences were presented using a non-cumulative (Word Fade = WF) self-paced word-by-word reading method (CRTT-R-WF). Reading times for the determiners and the correct nouns were analysed. Outcomes & Results: Both groups showed significantly longer reading times for the nouns than for determiners and in two-adjective than in one-adjective conditions. Furthermore, the reading times for the two-adjective condition were significantly longer than the one-adjective condition for nouns but not determiners across the groups. The PWA exhibited significantly longer overall reading times, as well as significantly longer reading times on the nouns than the NAI. Conclusions: Increased linguistic integration costs—imposed by greater amounts of material to be integrated, and appearing at the point where integration must take place—differentiated reading-time performance between the NAI and PWA participant groups. The PWA showed differentially longer online processing times for elements that imposed high integration costs. This difference appeared most dramatically when two adjectives intervened between the determiner and the head noun. The current results are consistent with resource-related hypotheses regarding aphasic language deficits, which suggest that PWA with limited control of processing resources should show differentially greater impairments in sentence processing as compared to NAI.

Working Memory and Its Relation to Auditory Comprehension in Native and Nonnative Speakers

Abstract There is a relatively robust and continually growing literature addressing the hypothesis that working memory (WM) competencies play an important role in language comprehension. This hypothesis has been investigated as the source for the language comprehension deficits that are a hallmark of aphasia. Additionally, it has been hypothesized that individuals with limited WM facility are negatively affected in second language acquisition and language use. The current study investigated this latter hypothesis and explored the relationship between working memory and sentencelevel auditory language comprehension in native English (L1) speakers with English as their first language and nonnative English (L2) speakers with Korean as their first and English as their second language. It was hypothesized that individuals who demonstrate poorer performance on measures of WM would perform more poorly on sentence comprehension tasks that are more difficult as manipulated by presentation rate and linguistic complexity, and these relationships would emerge more prominently in the L2 group than the L1 group. The results showed that WM performance significantly predicted auditory comprehension performance under all conditions in both high and lower functioning WM groups. As hypothesized, the L2 low-WM group performed significantly more poorly on the syntactically more complex sentences than the L2 high-WM group. However, the WM group effects were not present in the L1 group. Manipulations of presentation rates did not differentially affect auditory comprehension performance as a function of WM group either in the L1 or L2 groups.