No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Deficits in irregular past-tense verb morphology associated with degraded semantic knowledge
Abstract
Two distinct mechanisms are often considered necessary to account for generation of the past-tense of English verbs: a lexical associative process for irregular forms like speak spoke, and a rule-governed process ('add-ed') for regular and novel forms like talk talked and wug wugged. An alternative account based on a parallel-distributed processing approach proposes that one complex procedure processes all past-tense types. In this alternative view, neuropsychological dissociations are explained by reduced input from word meaning that plays a greater role in successful generation of the past-tense for lower frequency irregular verbs, and by phonological deficits that disproportionately affect regular and novel forms. Only limited evidence has been available concerning the relationship between knowledge of word meaning and verb-tense processing. The study reported here evaluated the past-tense verb abilities of 11 patients with semantic dementia, a neurodegenerative condition characterised by degraded semantic knowledge. We predicted and confirmed that the patients would have essentially normal ability to generate and recognise regular (and novel) past-tense forms, but a marked and frequency-modulated deficit on irregular verbs. Across the set of 11 patients, the degree of impairment for the irregular past-tense was significantly correlated with the degree of comprehension impairment as measured by verb synonym judgements. These results, plus other features of the data such as the nature of the errors to irregular verbs, are discussed in relation to currently developing theories of the language system.
... On the other hand, where this has been evaluated, patients with SD are typically impaired on some cognitive processes that are usually thought to be performed largely without reference to or need for conceptual knowledge: the ''presemantic'' cognition in the title of this article. Six examples of such impairments in SD are: reading aloud single written words (Fushimi et al., 2003;Funnell, 1996;); spelling single spoken words (Graham, Patterson, & Hodges, 2000;Parkin, 1993); transforming the stem (present tense) forms of verbs into their corresponding past-tense forms (Patterson, Lambon Ralph, Hodges, & McClelland, 2001;Cortese, Balota, Sergent-Marshall, Buckner, & Gold, in press); judging whether orthographically well-formed letter strings represent real words, that is, lexical decision (Moss, Tyler, Hodges, & Patterson, 1995;Diesfeldt, 1992); judging whether line drawings of possible objects represent objects that really exist, that is, object decision (Hovius, Kellenbach, Graham, Hodges, & Patterson, 2003;Breedin, Saffran, & Coslett, 1994); and reproducing simple line drawings of familiar objects after a short (e.g., 10 sec) delay (Bozeat et al., 2003;Lambon Ralph & Howard, 2000). The SD deficit in each of these processes follows a specific and common pattern in which—provided that the stimulus materials were selected to enable evaluation of these factors—performance is characterized by a strong frequency-by-typicality interaction. ...
... We had results from age-and education-matched healthy individuals for each of the six experimental tasks (with identical materials) from previous research, and the claim about the importance of data on all tasks from the same participants does not seem to apply to normal individuals; therefore, no new control data were collected for this study. The control data to which the patients' performance was compared come from the following published studies: for both reading aloud and spelling to dictation, with n = 24 normal participants each,Graham et al. (2000); for verb inflection with n = 10,Patterson et al. (2001); for both lexical decision (n = 11) and object decision (n = 10), Rogers, Lambon Ralph, Hodges, et al. (2004); and for delayed copy drawing (n = 4),Bozeat et al. (2003). ...
... For test administration, the experimenter dictated each word (with the list in random order) and first asked the patient to repeat the item to ensure that it had been heard correctly. The verb inflection test consisted of the 100 verbs fromPatterson et al. ( 2001), with 25 items in each of the four conditions formed by crossing word frequency (high vs. low) and regularity of past-tense structure (regular vs. irregular). For administration of the test, the participant first simultaneously heard and saw a short sentence in which the target verb was used in its stem/present-tense form, for example, ''Today I eat lunch.'' ...
... Les difficultés langagières qui sont observées dans la vsAPP sont diverses, et le fait qu'elles puissent toutes être entraînées par l'atteinte de la mémoire sémantique ne fait pas consensus. En effet, outre les difficultés de compréhension des mots isolés et l'anomie en dénomination et en langage spontané qui sont au coeur du portrait clinique, la vsAPP peut aussi s'accompagner (entre autres) de difficultés de lecture et d'écriture [15][16][17], de reconnaissance des mots [18,19] et de conjugaison des verbes (morphologie flexionnelle) [20][21][22][23][24]. Il est désormais admis que la mémoire sémantique joue un rôle important dans la lecture et l'écriture des mots irréguliers, dont la production ne peut reposer sur l'application des règles de correspondance grapho-phonémiques [15][16][17]. ...
... Plusieurs chercheurs rapportent la présence de difficultés de morphologie flexionnelle dans la vsAPP, touchant principalement la conjugaison des verbes irréguliers, et plus particulièrement ceux de basse fréquence [20][21][22][23][24]. Ces résultats sont controversés pour deux raisons. ...
... Deuxièmement, les atteintes de la morphologie ne sont pas observées chez tous les patients et semblent principalement présentes chez ceux dont la maladie est à un stade plus avancé et qui présentent une atteinte plus sévère [29,30]. Certains chercheurs attribuent ce fait à l'aggravation de l'atteinte de la mémoire sémantique [21,22] et à l'atrophie des lobes temporaux antérieurs [24]. Selon certaines propositions théoriques [14], les lobes temporaux antérieurs seraient le siège d'une zone amodale de convergence ou hub d'un réseau interconnecté d'aires sensorielles, motrices et linguistiques [14]. ...
Résumé. Des recommandations consensuelles donnant une description des critères permettant de poser le diagnostic des trois variantes d’aphasie primaire progressive (APP) ont été publiées en 2011. Depuis leur publication, ces recommandations ont fait l’objet de critiques qui ont récemment mené à la proposition de leur révision. Cet article propose une description des ensembles de critères qui ont précédé les recommandations consensuelles utilisées actuellement, ainsi qu’un état de la question quant aux différentes limites et controverses entourant la description du profil langagier des trois variantes d’APP. Ces controverses seront examinées sous l’angle de la description des manifestations centrales de chaque variante, de leur diagnostic différentiel, des liens entre les différentes entités cliniques et leur pathologie sous-jacente, ainsi que de l’évolution des profils langagiers. Enfin, cet article propose des perspectives quant à l’évaluation du langage dans les APP qui ont plusieurs implications pour la pratique clinique et la recherche.
Abstract. Consensual recommendations for the diagnostic criteria of three variants of primary progressive aphasia (PPA) were published in 2011. Since their publication, these recommendations were the object of criticism, which has recently led to the proposition of their revision. This article gives a description of the criteria that preceded the consensual criteria currently in use, and presents the different limits and controversies regarding the description of each PPA variant’s language profile. These controversies will be examined in terms of the description of each variant’s central manifestations, their differential diagnosis, the links between each clinical entity and its underlying pathology, and the evolution of the language profile. Lastly, this article offers perspectives regarding language evaluation in PPA that have several implications for clinical practice and research.
... In this approach, the prediction of a double dissociation in impaired past tense processing follows from the combination of greater phonological complexity of the regular than the irregular past tense, plus a hypothesised greater reliance of irregular forms on a contribution from word meaning. In this account, therefore, the pattern of irregular > regular should be associated with a general phonological impairment, while the pattern of regular > irregular is predicted from a general semantic deficit (Joanisse & Seidenberg, 1999;Patterson, Lambon Ralph, Hodges, & McClelland, 2001). ...
... Thus a frequency by regularity interaction results, with low frequency, irregular forms causing relatively selective difficulty. This is precisely the pattern found in a study of the generation and recognition of past tense verbs in semantic dementia ( Patterson et al., 2001). ...
... More of a problem for any dual mechanism account seem to be errors which combine regular and irregular elements in a single response (tored, frozed). If access to the correct past tense form (here tore and froze) is supposed to block application of the regular rule in the procedural system, then such errors should not occur; but nearly 10% of the irregular past tense errors in Patterson et al. (2001) were of this form. ...
... There are rules for conjugating these two tenses, but there are also many irregular verbs. We predicted that analogous to surface dyslexia in English, German patients with svPPA would regularize irregular verbs in inflectional morphologya prediction that is, furthermore, anticipated from studies in English showing that patients with svPPA regularize the past-tense inflectional morphology of irregular verbs (Patterson, Lambon Ralph, Hodges, & McClelland, 2001). Moreover, because the robustness of knowledge in semantic memory is influenced by frequency, we predicted that regularization would be more apparent (a) in lowerfrequency verbs and also (b) in the less frequently used preterite, compared with the perfect, tense. ...
... Therefore, it seems safe to say that the results are consistent with past studies showing a general interaction effect between frequency and regularity in verb inflection that can even be seen in oral production in HCs (Seidenberg, 1992;Woollams, Joanisse, & Patterson, 2009). More specifically, the svPPA results are consistent with past studies showing that frequency and regularity have a crucial impact on correct verb inflection (Auclair-Ouellet, 2015;Cortese et al., 2006;Patterson et al., 2001). Indeed, the svPPA group had worse performance in the inflection of irregular verbs in both tenses while showing relative preservation of low-frequency regular verbs. ...
Surface dyslexia, a diagnostic feature of the semantic variant of primary progressive aphasia (svPPA), is difficult to observe in many languages. It can be conceptualized as one manifestation of a more general “regularization” effect—that is, with semantic impairment, patients fail to recognize exceptions and revert to default rules. Objective: We predicted that, analogous to surface dyslexia in English, German patients with svPPA would regularize irregular verbs, especially those of lower frequency and in the less frequently used preterite tense. Method: Regularization was investigated in German through past-tense verb inflectional morphology in N = 10 svPPA, N = 5 PPA related to Alzheimer pathology (Aß+PPA), N = 5 patients with nonfluent variant PPA (nfvPPA), N = 12 typical (amnestic presentation) Alzheimer’s disease (AD), and N = 32 healthy controls. The task involved perfect- and preterite-tense inflection of regular and irregular verbs of high and low frequency. Results: Errors in svPPA particularly involved regularization (e.g., I swim → I swimmed, I have swimmed), whereas Aß+PPA made a wide range of other errors (e.g., verb agreement or tense errors). Regularization was rare in AD and controls, whereas the expected frequency effects (low worse than high) were found in svPPA. nfvPPA had profound difficulties in inflecting verbs in general. Conclusion: The study illustrates how tests tailored to a specific language can reveal the regularization effect of svPPA. For more universal diagnostic recommendations, future revisions for svPPA should consider substituting the criterion of surface dyslexia for that of a general criterion of regularization of language rules, the former being an example of the latter.
... One major source of evidence in this area comes from adult language disorders consequent on brain injury or disease. Patients with different aphasic profiles have been reported to constitute the two sides of a double dissociation, i.e., some with a significant advantage for regular > irregular and some with the opposite pattern (Bird, Lambon Ralph, Seidenberg, McClelland, & Patterson, 2003;Marslen-Wilson & Tyler, 1997;Patterson, Lambon Ralph, Hodges, & McClelland, 2001;Tyler, de Mornay Davies et al., 2002;; Ullman et al., 1997). By the logic of standard neuropsychological inquiry (Shallice, 1988), double dissociation requires a conclusion of separate mechanisms, although this is not the only interpretation available (Plaut, 1995). ...
... The results of this study are intended to be viewed as part of a package with two previous studies by our re Table 8 PatientsÕ accuracy for repetition and naming of bisyllabic words that vary in stress position search group ( Bird et al., 2003;Braber et al., in press), all aimed at an attempt to understand the nature of the past-tense verb deficit in patients with non-fluent aphasia. The theoretical position guiding all of these studies (and indeed a further one on the nature of the past-tense verb deficit in patients with semantic deficits: Patterson et al., 2001) is as follows: for neuropsychological dissociations between regular and irregular pasttense verbs, as well as other forms of evidence regarding past-tense performance, a model based on a single integrated language system with distinctive phonological and semantic contributions (Joanisse & Seidenberg, 1999;McClelland & Patterson, 2002) may provide a more promising account than a model of separate mechanisms for regular and irregular verbs (Pinker, 1999;Pinker & Ullman, 2002;Tyler, de Mornay Davies et al., 2002;). ...
The disadvantage in producing the past tense of regular relative to irregular verbs shown by some patients with non-fluent apha-sia has been alternatively attributed (a) to the failure of a specific rule-based morphological mechanism, or (b) to a more generalised phonological impairment that penalises regular verbs more than irregular owing to the on-average greater phonological complexity of regular past-tense forms. Guided by the second of these two accounts, the current study was designed to identify more specific aspects of phonological deficit that might be associated with the pattern of irregular > regular past-tense production. Non-fluent aphasic patients (N = 8) were tested on past-tense verb production tasks and assessed with regard to the impact of three main manipulations in other word-production tasks: (i) insertion of a delay between stimulus and response in repetition; (ii) presence/ number of consonant clusters in a target word in repetition; (iii) position of stress within a bi-syllabic word in repetition and picture naming. The performance of all patients deteriorated in delayed repetition; but the patients with the largest discrepancy between regular and irregular past-tense production showed greater sensitivity to the other two manipulations. The phonological nature of the factors that correlated with verb-inflection performance emphasises the role of a phonological deficit in the observed pattern of irregular > regular.
... Other cognitive functions, including phonology, syntax, executive skills and episodic memory, remain relatively intact in this condition. Nevertheless, SD patients show a highly predictable pattern of breakdown on a number of tasks typically thought to be "pre-semantic", including reading single words aloud (Funnell, 1996;Patterson and Hodges, 1992;Woollams et al., 2007); spelling to dictation (Graham et al., 2000;Parkin, 1993); producing the past tense form of verbs from the present tense (Cortese et al., 2006;Patterson et al., 2001); lexical decision (Moss et al., 1995;Rogers et al., 2004b); immediate serial recall of short lists of words (Jefferies et al., 2004;Jefferies et al., 2005;Knott et al., 1997;Knott et al., 2000); object decision, i.e. deciding if line drawings represent real objects (Breedin et al., 1994;Hovius et al., 2003;Rogers et al., 2003;Rogers et al., 2004b) and copying drawings of objects after a brief delay (Bozeat et al., 2003;Lambon Ralph and Howard, 2000). ...
... Five SA patients were compared with the SD group. One hundred verbs from Patterson et al. (2001) were used. There were 25 items in four conditions that crossed word frequency (high vs. low) and typicality (regular vs. irregular). ...
Patients with semantic dementia show a specific pattern of impairment on both verbal and non-verbal “pre-semantic” tasks, e.g., reading aloud, past tense generation, spelling to dictation, lexical decision, object decision, colour decision and delayed picture copying. All seven tasks are characterised by poorer performance for items that are atypical of the domain and “regularisation errors” (irregular/atypical items are produced as if they were domain-typical). The emergence of this pattern across diverse tasks in the same patients indicates that semantic memory plays a key role in all of these types of “pre-semantic” processing. However, this claim remains controversial because semantically impaired patients sometimes fail to show an influence of regularity. This study demonstrates that (a) the location of brain damage and (b) the underlying nature of the semantic deficit affect the likelihood of observing the expected relationship between poor comprehension and regularity effects. We compared the effect of multimodal semantic impairment in the context of semantic dementia and stroke aphasia on the seven “pre-semantic” tasks listed above. In all of these tasks, the semantic aphasia patients were less sensitive to typicality than the semantic dementia patients, even though the two groups obtained comparable scores on semantic tests. The semantic aphasia group also made fewer regularisation errors and many more unrelated and perseverative responses. We propose that these group differences reflect the different locus for the semantic impairment in the two conditions: patients with semantic dementia have degraded semantic representations, whereas semantic aphasia patients show deregulated semantic cognition with concomitant executive deficits. These findings suggest a reinterpretation of single-case studies of comprehension-impaired aphasic patients who fail to show the expected effect of regularity on “pre-semantic” tasks. Consequently, such cases do not demonstrate the independence of these tasks from semantic memory.
... Patients with frontal damage, as a result of stroke [18] or Parkinson's disease [19] tend to have problems with the regulars. In contrast, patients with damage to inferior temporal cortex, either because they suffer from semantic dementia [7,11] Herpes Simplex Encephalitis [18] or Alzheimers disease [19], have problems with the irregulars. This combination of behavioural deficits and their association with damage to specific cortical regions provides clear support for two distinct systems underlying the processing of the regular and irregular past tense, and by extension, other aspects of language that can be distinguished in this way. ...
... [5,13]). The view that we will consider here, since it is not only directly addressed to the regular/irregular past tense distinction in English, but also places a similar emphasis to our account on the role of phonological deficits, is the model recently proposed by Joanisse and Seidenberg [4], and adopted in slightly modified form by Patterson et al. [11]. On this account, past tense dissociations are to be explained in terms of damage to a single system in which the speech input is mapped directly onto a set of distributed representations with a specific architecture of connections, modelling words in terms of their speech input, speech output, and semantics. ...
The double dissociation between the regular and irregular past tense in English has been explained in terms of dual and single mechanism accounts. In previous research we have argued that problems with the regular past tense in patients with left inferior frontal damage arise from morpho-phonological parsing difficulties [Trends in Cognitive Science 2 (1998) 428]. This claim has recently been challenged by a single mechanism connectionist account which argues that a general phonological processing deficit causes the poor performance on the regular past tense, with morphological factors playing no explicit role [Proceedings of the National Academy of Sciences 96 (1999) 7592]. We used a speeded judgement task with four patients who have documented difficulties with the regular past tense to contrast the claims made by these different approaches. We compared patients' ability to detect the difference between the past tense and stem of regular (hugged/hug) and irregular (taught/teach) past tense verbs, as well as matched "pseudo" pairs (trade/tray and port/peach). These real word conditions were accompanied by matched sets of non-words (e.g. nugged/nug). Patients' latencies to the regular past tense real word-pairs were consistently slower than in any other condition. To test for a general phonological processing deficit, we conducted several tests of phonological processing ability. The results show that the patients had a range of difficulties in phonological processing, from very mild to severe. This did not correlate with their performance on the speeded judgement task. We interpret this pattern of results as support for a specialised morpho-phonological processing mechanism which can be dissociated from other phonological processes and which is used directly in the processing of the regular past tense in a dual-mechanism system.
... From this viewpoint, dissociations are clear evidence that the underlying mechanisms differ across types of verbs. Recent discussions, however, suggest that such dissociations do not provide sufficient evidence when deciding between single and dual mechanism models [Mc-Clelland and Patterson, 2002a,b;Seidenberg and Arnoldussen, 2003b], because: (1) dissociations might merely be an epiphenomenon of the differences in phonological and semantic overlap between the studied forms [Bird et al., 2003;Joanisse and Seidenberg, 1999;McClelland and Patterson, 2003;Patterson et al., 2001;Seidenberg and Arnoldussen, 2003b], and (2) an increasing amount of data from brain-lesioned patients of different languages have shown patterns of performance counter to those expected by dual models in Spanish [De Diego Balaguer et al., 2004], Italian [Laiacona and Caramazza, 2004], English [Faroqi-Shah and Thompson, 2003;Shapiro and Caramazza, 2003], Greek [Tsapkini et al., 2000], and German [Penke et al., 1999]. In addition, imaging studies have shown areas activated by both regular and irregular inflectional processing, particularly in frontal regions [Beretta et al., 2003;Jaeger et al., 1996;Rhee et al., 2001;Sahin et al., 2006;Ullman et al., 1997a]. ...
... Dual models state that regular forms are generated by the application of a default rule and thus demand grammatical processing [Clahsen, 1999;Pinker and Ullman, 2002]. In contrast, single system accounts argue that the information underlying the production of regular forms is in fact the same as that needed for irregular verbs, but that phonological information weighs more heavily in these words [Bird et al., 2003;Joanisse and Seidenberg, 1999;Patterson et al., 2001]. In light of these predictions, using event-related functional magnetic resonance imaging (fMRI), the present study evaluated the involvement of language-related brain regions in the processing of regular and irregular verbs. ...
Many languages, including English and Spanish, feature regular (dance --> danced) and irregular (catch --> caught) inflectional systems. According to psycholinguistic theories, regular and irregular inflections are instantiated either by a single or by two specialized mechanisms. Those theories differ in their assumptions concerning the underlying information necessary for the processing of regular verbs. Whereas single mechanism accounts have stated an increased involvement of phonological processing for regular verbs, dual accounts emphasize the prominence of grammatical information. Using event-related functional magnetic resonance imaging, we sought to delineate the brain areas involved in the generation of complex verb forms in Spanish. This language has the advantage of isolating specific differences in the regular-irregular contrasts in terms of the number of stems associated with a verb while controlling for compositionality (regular and irregular verbs apply suffixes to be inflected). The present study showed that areas related to grammatical processing are active for both types of verbs (left opercular inferior frontal gyrus). In addition, major differences between regular and irregular verbs were also observed. Several areas of the prefrontal cortex were selectively active for irregular production, presumably reflecting their role in lexical retrieval (bilateral inferior frontal area and dorsolateral prefrontal cortex). Regular verbs, however, showed increased activation in areas related to grammatical processing (anterior superior temporal gyrus/insular cortex) and in the left hippocampus, the latter possibly related to a greater implication of the phonological loop necessary for the reutilization of the same stem shared across all forms in regular verbs.
... Similarly, linguists standardly distinguish between forms that are generated by grammatical rules (e.g., the past tense of BAKE) and forms that are stored in lexical memory (e.g., the past tense of TAKE; seeAnderson, 1988;Spencer, 1991). According toPinker (2000), the stored and generated forms involve completely different mechanisms; although this claim is controversial (seeJoanisse & Seidenberg, 1999;Patterson et al., 2001), the theoretical distinction is clear.Coltheart et al.'s (2001)model also illustrates the distinction: The pronunciations of nonwords are generated by grapheme–phoneme correspondence rules, whereas the pronunciations of words are stored as nodes in a phonological lexicon. The distinction is clear, but the point is that it does not apply to our model. ...
... Like the phonetic features, the semantic features also have heuristic value: They have been shown to provide a good approximation to the kinds of information that are initially activated when words are read, as indexed by measures such as semantic priming (McRae & Boisvert, 1998;McRae, de Sa, & Seidenberg, 1997;Plaut & Booth, 2000). These representations have also been used to understand selective patterns of semantic impairment following brain injury, the progressive loss of semantic information due to degenerative neuropathology, and the neural bases of semantics (Gainotti, 2000;Hinton & Shallice, 1991;Patterson & Hodges, 1992;Patterson, Lambon Ralph, Hodges, & McClelland, 2001). As in the case of phonetic features, we assume that the featural semantic representations are approximate; that semantic phenomena will ultimately be explained in terms of more basic biological and experiential factors; and that such a theory will explain the featuresque aspects of behavior identified in studies such as the aforementioned ones. ...
this article should be addressed to Michael W. Harm, mharm@stanford.edu or Mark S. Seidenberg, marks@lcnl.wisc.edu
... Characteristics of irregular past tense forms may assist in explaining the distinction. For example, irregular past tense forms appear less frequently in the English language than regular past tense forms (Nicoladis, Palmer, & Marentette, 2007) and have been associated with semantic knowledge (Patterson, Lambon Ralph, Hodges, & McClelland, 2001) and declarative memory (Ullman, 2001). The CALP measure employed in this study (the WMLS-NU) is a measure of semantic skill. ...
This Element provides an overview of research considering variables deemed to impact bilingual language acquisition, and highlights research outcomes from a variety of disciplines. An exploratory study takes into account these variables and examines the language acquisition of adult Spanish-English bilinguals across a range of domains in their two languages. The results demonstrate that the highly interactive nature of bilingual speakers' languages is in line with a holistic view of the dynamic, interdependent nature of bilingualism as described by usage-based theories and dynamic systems theories, and by the conceptualization of bilingual language from a Dynamic Interactive Processing Perspective.
... Consequently, Joanisse & Seidenberg (1999) suggest that the selective deficit in irregular inflected forms reported in Ullman et al. (1997Ullman et al. ( , 2005) might be due to semantic deficits in the patients investigated. In support of the triangle model, Patterson et al. (2001) presented data from patients with semantic dementia who encountered more difficulties with irregular than with regular verbs in a past tense elicitation task. In contrast, damage to the phonological layer in the network proposed by Joanisse & Seidenberg (1999) affects the generation of past tense forms, for regular as well as novel verbs that are generated by analogy to similar phonological forms within this account. ...
Regular and inflectional morphology are often selectively affected in acquired or developmental language disorders. The observed cases of selective deficits have been used as evidence for prominent models of language representation in the brain. Dualistic approaches to language and inflection propose separate mechanisms for rule-based regular inflection and stored irregular inflection. Single mechanism accounts, in contrast, represent all aspects of language including inflection within a uniform network architecture. These contrasting accounts, however, converge on the assumption that regular and irregular inflected forms can be differentially affected in neurological disorders such as non-fluent and fluent aphasia. Due to different lesion sites (frontal vs. temporo-parietal lesions) and/or different clinical symptoms (phonological vs. lexical-semantic deficits) associated with these disorders, it is assumed that in most patients with Broca’s aphasia and Parkinson’s disease regular inflection is more affected than irregular inflection, whereas in fluent aphasic patients such as Wernicke’s aphasics irregular inflected forms are more severely impaired than regular inflected forms. While these dissociative patterns have been observed in English patients, research on language impaired speakers of other languages has often found impairment profiles different from English. A point in case is German. Here we report data on the elicited production of regular and irregular participle and noun plural forms in German subjects with Wernicke’s and Broca’s aphasia, Parkinson’s disease and age-matched healthy subjects. The results indicate a selective deficit with accessing irregular inflected word forms that seems independent of particular neurological syndromes and their underlying brain lesions. Our data suggest that for all subject groups, difficulties in memory access are the underlying common source for errors in producing infrequent irregular inflected forms stored in the mental lexicon.
... Consequently, Joanisse & Seidenberg (1999) suggest that the selective deficit in irregular inflected forms reported in Ullman et al. (1997Ullman et al. ( , 2005) might be due to semantic deficits in the patients investigated. In support of the triangle model, Patterson et al. (2001) presented data from patients with semantic dementia who encountered more difficulties with irregular than with regular verbs in a past tense elicitation task. In contrast, damage to the phonological layer in the network proposed by Joanisse & Seidenberg (1999) affects the generation of past tense forms, for regular as well as novel verbs that are generated by analogy to similar phonological forms within this account. ...
... There is no shifting between mechanisms. For example, the point of departure for a PDP account of the apparent effect of inflectional regularity would focus on the consequences of greater orthographic overlap between prime and target for regularly than for irregularly inflected verbs (e.g., Bird et al. 2003;Bybee & McClelland, 2005;Patterson, Lambon Ralph, Hodges, & McClelland, 2001;Plaut, McClelland, Seidenberg, & Patterson, 1996). Also relevant is greater semantic connectedness among irregularly than regularly inflected verbs (devoid of any prime) as this influences the starting point for recognition (Baayen & Moscoso del Prado Mart.n, 2005). ...
We differentiate between lexicon-based and learning-based models of lexical access and representation and describe how each accounts for morphological effects in early and late word recognition. Then we select from the experimental evidence with behavioral and electrophysiological measures in the lexical decision task to portray the debate about how morphologically complex words are recognized. We highlight data about inflections and derivations not only in English but also in other languages (German, Hebrew) to demonstrate how cross-linguistic comparisons can enrich models of morphological processing.
... This phenomenon is observed across a whole range of tasks, including reading aloud (where patients will correctly pronounce typical words such as "new" but will read "sew" as "sue"), 84 spelling of spoken words (correct spelling of typical words like "stem" or "blink" but errors like "blood" spelled "blud" or "scissors" spelled "sizzers"), 85 and generation of the past tense forms of verbs (correct inflection of typical verbs like "talk" as "talked" but typicalisation errors to irregular verbs; thus, the past participle of "drink" becomes "drinked" instead of "drank"). 86 This kind of typicalisation error has an equivalent in the object domain. For example, when a patient with SD was asked to copy a drawing of a peacock with the stimulus picture present, he showed good copying skills (figure 2). ...
Semantic dementia (SD), one of the main clinical variants of frontotemporal dementia, presents a unique combination of clinical and imaging abnormalities. We describe the epidemiological, cognitive, and radiological features of SD. The distinctive and consistent neuropsychological deficits in this disorder have had a major effect on current conceptions of the organisation of semantic memory and its links to episodic memory, language, and perceptual processes. Structural (MRI) and functional (fluorodeoxyglucose-PET) studies in SD emphasise the role of the temporopolar and perirhinal cortices. Unlike other frontotemporal dementia syndromes, the neuropathological findings in SD are fairly predictable: most patients have ubiquitin-positive, tau-negative neuronal inclusions.
... This phenomenon is observed across a whole range of tasks, including reading aloud (where patients will correctly pronounce typical words such as "new" but will read "sew" as "sue"), 84 spelling of spoken words (correct spelling of typical words like "stem" or "blink" but errors like "blood" spelled "blud" or "scissors" spelled "sizzers"), 85 and generation of the past tense forms of verbs (correct inflection of typical verbs like "talk" as "talked" but typicalisation errors to irregular verbs; thus, the past participle of "drink" becomes "drinked" instead of "drank"). 86 This kind of typicalisation error has an equivalent in the object domain. For example, when a patient with SD was asked to copy a drawing of a peacock with the stimulus picture present, he showed good copying skills (figure 2). ...
Semantic dementia (SD), one of the main clinical variants of frontotemporal dementia, presents a unique combination of clinical and imaging abnormalities. We describe the epidemiological, cognitive, and radiological features of SD. The distinctive and consistent neuropsychological deficits in this disorder have had a major effect on current conceptions of the organisation of semantic memory and its links to episodic memory, language, and perceptual processes. Structural (MRI) and functional (fluorodeoxyglucose-PET) studies in SD emphasise the role of the temporopolar and perirhinal cortices. Unlike other frontotemporal dementia syndromes, the neuropathological findings in SD are fairly predictable: most patients have ubiquitin-positive, tau-negative neuronal inclusions.
... Unsurprisingly, our report of ILJ's impairments in these aspects of language processing does not constitute absolutely the first hint that these abilities might be compromised in SD. For example, (1) difficulty in producing inflectional morphology, specifically the past tense of irregular verbs in English, has been documented in a group of SD cases (Patterson et al., 2001), although a recent study has demonstrated normal morphological/semantic priming from both regular and irregular past-tense verbs to their stem forms (Tyler et al., 2004, JCN). ...
... This effect is particularly important for low-frequency words. Similar deficits are seen in forming the past tense of irregular verbs 40 ; here too, SD patients make regularization errors on low-frequency irregular items, perhaps because semantic connections are relied upon only for low-frequency words, whereas other mechanisms such as neighbor effects (mini-families of phonologically sim- ilar verbs [eg, ''blow,'' ''throw,'' ''know'' . ''blew,'' ''threw,'' ''knew'']) are sufficient for the more common items. ...
The relationship between semantic dementia (SD) and primary progressive aphasia (PPA) has been the subject of debate ever since the syndromes were first described, in converging streams of research from the neuropsychological and neurologic communities. The most salient clinical features of SD are anomia with circumlo-cution and semantic paraphasia, single-word comprehension deficit, and reduced category fluency. Of critical importance is the fact that patients also show deficits on non-verbal tasks using visual, auditory, and other modalities, suggesting that the key impairment in SD is a breakdown in conceptual knowledge rather than a specific problem with language. The finding of item consistency between the various tests supports this view. The order in which the features appear can be explained by the variable degree of redundancy in access to semantic knowledge from the different perceptual modalities. Atrophy is seen in the anterior and inferior temporal lobe rather than in classic language areas, further distancing SD from aphasic syndromes. Semantic dementia and progressive non-fluent aphasia (PNFA) share some clinical and pathologic characteristics with frontal variant frontotem-poral dementia, but there are also clear differences between the three syndromes. We believe that many patients described as having fluent primary progressive aphasia in fact have early SD. Semantic dementia is a well-defined syndrome, distinct from PNFA but related to it within the spectrum of frontotemporal lobar degeneration syndromes.
... As it is already known that regions that are not themselves structurally damaged can be functionally abnormal in SD (Mummery et al., 2000) and, indeed, in any form of brain disease or damage, even a clear demonstration that the atrophied regions do not include the putative location of the structural description system does not rule out this first interpretation. Our reason for rejecting it relies not on the results presented here but rather on findings from multiple studies of SD establishing deficits on tasks in many different cognitive domains that are not thought to be primarily semantic—tasks such as reading single words aloud (McCarthy & Warrington, 1986), immediate serial recall of word sequences (Patterson, Graham, & Hodges, 1994), transforming present tense verbs into the past tense (Patterson, Lambon Ralph,Hodges & McClelland, 2001), copying pictures of objects after a brief delay (Lambon Ralph & Howard, 2000), and so on. If all of these disparate deficits form a consistent cluster in SD, a hypothesis of associated but unrelated impairments begins to seem cumbersome and implausible. ...
The authors investigated the impact of semantic knowledge on visual object analysis by assessing the performance of patients with semantic dementia on a different-views object matching test and on 2 object decision tests differing, for example, in whether the nonreal items were nonsense objects or chimeras of 2 real objects. On average, the patients scored normally on both the object matching and the object decision test including nonsense objects but were impaired on the object decision test including chimeras; this latter was also the only visual object test that correlated significantly with degree of semantic impairment. These findings demonstrate that object decision is not a single task or ability and that it is not necessarily independent of conceptual knowledge.
... Conversely, the presence of agrammatism and motor speech abnormalities are features of agPPA and PAOS that are typically absent in lvPPA, as we observed in our cohort (Supplemental Table 1). Deficits in reading irregular words have been associated with svPPA (Patterson et al., 2001). A couple of other studies have also investigated clinical features that help predict Aβ deposition. ...
Beta-amyloid (Aβ) deposition can be observed in primary progressive aphasia (PPA) and progressive apraxia of speech (PAOS). While it is typically associated with logopenic PPA, there are exceptions that make predicting Aβ status challenging based on clinical diagnosis alone. We aimed to determine whether MRI regional volumes or clinical data could help predict Aβ deposition. One hundred and thirty-nine PPA (n = 97; 15 agrammatic, 53 logopenic, 13 semantic and 16 unclassified) and PAOS (n = 42) subjects were prospectively recruited into a cross-sectional study and underwent speech/language assessments, 3.0 T MRI and C11-Pittsburgh Compound B PET. The presence of Aβ was determined using a 1.5 SUVR cut-point. Atlas-based parcellation was used to calculate grey matter volumes of 42 regions-of-interest across the brain. Penalized binary logistic regression was utilized to determine what combination of MRI regions, and what combination of speech and language tests, best predicts Aβ (+) status. The optimal MRI model and optimal clinical model both performed comparably in their ability to accurately classify subjects according to Aβ status. MRI accurately classified 81% of subjects using 14 regions. Small left superior temporal and inferior parietal volumes and large left Broca's area volumes were particularly predictive of Aβ (+) status. Clinical scores accurately classified 83% of subjects using 12 tests. Phonological errors and repetition deficits, and absence of agrammatism and motor speech deficits were particularly predictive of Aβ (+) status. In comparison, clinical diagnosis was able to accurately classify 89% of subjects. However, the MRI model performed well in predicting Aβ deposition in unclassified PPA. Clinical diagnosis provides optimum prediction of Aβ status at the group level, although regional MRI measurements and speech and language testing also performed well and could have advantages in predicting Aβ status in unclassified PPA subjects.
... Reading written words aloud: semantic deficit yields regularization reading errors like sew -"sue" (Patterson and Hodges, 1992;Woollams et al, 2007) Writing to dictation: semantic deficit yields regularization spelling errors like "cough"coff (Graham et al, 2000) Transforming the root or present tense form of a verb to its past tense: semantic deficit yields regularization errors like "drink" -"drinked" (Patterson et al, 2001) The principle in explaining this relationship, however, is in a sense not the semantic deficit itself but the failure of semantic information to reach, affect, and constrain the response. Of course, a semantic deficit per se will have this effect; but we would also expect a similar "surface" pattern of responding in a patient with reasonably preserved semantic knowledge but a major problem in activating phonology or orthography from semantics. ...
This brief paper, inspired by an invitation to acknowledge and celebrate Oscar Marin's great contributions to cognitive neurology and neuropsychology, reviews the case of a patient, T.P., who had significant deficits of naming, reading, and spelling. I first studied and reported this patient 35 years ago, in 1979, when I was significantly influenced by the work of Oscar Marin and his colleagues. I have recently had the unusual opportunity to do some brief reassessment of T.P.'s current (2015) cognitive abilities, and to reassess the interpretations that I had given to her pattern of impairment in the initial studies. I suggest that advances over the last decade or soin theorizing about, and connectionist modeling of, reading and spelling disordersenable a more coherent account of T.P.'s acquired anomia, dyslexia, and dysgraphia, and the relationships among them.
... A second theoretical perspective of regular and irregular forms posits that the processing of all inflected forms depends on associative pattern matching (Bybee, 1985;Joanisse & Seidenberg, 1999;McClelland & Patterson, 2002a;Rumelhart & McClelland, 1986;Seidenberg, 1997). One such account, while relying on a single computational mechanism, nonetheless makes explicit predictions regarding dissociations between regular and irregular inflected forms and the brain regions they depend on (Joanisse & Seidenberg, 1999;McClelland & Patterson, 2002a;Patterson, Lambon Ralph, Hodges, & McClelland, 2001). On this view, the production of irregular past tenses depends particularly on word meanings that rely on temporallobe cortical regions, whereas the production of regular and novel past tenses is posited instead to show a greater reliance on phonology and frontal lobe regions. ...
... There is now considerable evidence that the anterior temporal lobes (ATLs) play critical roles in representing both object concepts and action concepts, regardless of whether those meanings are probed with spoken words, written words, pictures, or other types of stimuli (object concepts: Binney, Embleton, Jeffries, Parker, & Lambon Ralph, 2010;Clarke & Tyler, 2014;Kivisaari, Tyler, Monsch, & Taylor, 2012;Lambon Ralph, Ehsan, Baker, & Rogers, 2012;Lambon Ralph, Pobric, & Jefferies, 2009;Lambon Ralph, Sage, Jones, & Mayberry, 2010;Mayberry, Sage, & Lambon Ralph, 2011;Mion et al., 2010;Taylor, Moss, Stamatakis, & Tyler, 2006;Taylor, Stamatakis, & Tyler, 2009;action concepts: Bak & Hodges, 2003;Cotelli et al., 2006;Hillis et al., 2006;Patterson, Lambon Ralph, Hodges, & McClelland, 2001;Pulvermü ller et al., 2009;Yi, Moore, & Grossman, 2007). The exact nature of the ATLs' bilateral contribution to conceptual knowledge is not yet clear ( Wong & Gallate, 2012), but according to a prominent theory called the Hub and Spoke Model ( Lambon Ralph, 2014), these regions contain transmodal semantic devices ("hubs") that integrate and systematize the modality-specific features that comprise much of the concrete content of concepts and are scattered across the cortex in ways that reflect their sensory and motor origins ("spokes"). ...
... In the acquisition of the past tense children produce many overregularization errors such as comed but very few irregularizations (Marcus et al., 1992). Agrammatic aphasic patients have been argued to display selective deficits in the production of regular past tense forms (Ullman et al., 1997), whereas patients with semantic dementia show selective deficits in processing irregular forms (Patterson et al., 2001). Further dissociations between regular and irregular forms have been revealed in brain imaging studies (e.g.,Newman et al., 2002;Tyler et al., 2005). ...
We present a speeded production study of the English past tense that is designed to evaluate between conflicting theories of the mechanism of verb inflection. Test items are verbs that systematically differ in regularity but also in overall ease of processing as defined by a number of statistical and distributional factors. We show that overall ease, but not regularity, predicts differences in the response latencies of produced past tense forms in adults. These results indicate that the processing of inflections is best explained by a single, associative mechanism that is responsible for the production of all verbs.
... The lexicon must represent the information and procedures necessary to achieve the fluent generation of these forms, and psycholinguistic studies have demonstrated that the distinction between regular and irregular inflections has also consequences for word processing and lexical acquisition (for a review, see Marcus, 2000;Ullman 2001). Similarly, analyses of language impairments, both developmental and acquired, have demonstrated that regular and irregular inflectional processes can be selectively impaired (e.g., Cortese, Balota, SergentMarshall, Buckner, & Gold, 2006;Miozzo, 2003;Miozzo & Gordon, 2005;Patterson, Lambon-Ralph, Hodges, & McClelland, 2001;Penke, Janssen, & Krause, 1999;Tyler, Randall, & Marslen-Wilson, 2002; Ullman et al., 1997;Ullman & Gopnik, 1999). ...
Background: A few studies have recently documented cases of proficient bilingual individuals who, subsequent to neural injury, suffered selective deficits affecting specific aspects of lexical processing. These cases involved disruption affecting the production of words from a specific grammatical category (verbs or nouns) or the production of irregular versus regular verb forms. Critically, these selective deficits were manifested in a strikingly similar manner across the two languages spoken by each of the individuals.Aims: The present study aims at reviewing these cases of selective cross‐linguistic deficits and discussing their implications for theories concerning lexical organisation in the bilingual brain.Methods & Procedures: The studies reviewed here employed a variety of behavioural tests that were specifically designed to investigate the availability in aphasic patients of lexical information concerning nouns and verbs and their morphological characteristics.Outcomes & Results: The brain‐damaged bilingual speakers reviewed in the present study exhibited selective deficits for nouns, verbs, or irregularly inflected verbs in both of their languages.Conclusions: The selectivity and cross‐language nature of the deficits reviewed here indicates that at least certain language substrates are shared in proficient bilingual people. The fact that these deficits affect grammatical class distinctions and verb inflections—information that is part of the lexicon—further indicates that shared neural substrates support lexical processing in proficient bilingual people.
... Since that time too, a number of group studies have shown SD patients to be reliably and predictably impaired on several other purportedly 'non-semantic' tasks: past-tense verb transformations (Cortese et al., 2006;Patterson et al., 2001), spelling (Graham et al., 2000), delayed copy drawing (Bozeat et al., 2003;Lambon Ralph and Howard, 2000), lexical decision (Diesfeldt, 1992;Moss et al., 1995;Rogers et al., 2004) and object decision Rogers et al., 2004). In the first study to examine the performance of a group of SD patients on all six of these tasks, Patterson et al. (2006) observed not only that deficits co-occur on all tasks in the same patients but also that each of the tasks is affected in a similar, principled way. ...
Although semantic dementia (SD) is defined as a selective disruption of conceptual knowledge, a number of group studies have now demonstrated that SD patients also show impaired performance on tasks not usually considered to have a high semantic load (e.g., reading words aloud and lexical or object decision). The aim of the current study was to document the relative deterioration, over time, of a number of semantic and so-called 'non-semantic' tasks in LF, a single case of SD for whom - by virtue of his work as a published cartoonist - we also have extensive data regarding his pre-morbid linguistic and drawing skills. In five testing rounds over a period of five years we administered semantic tests of object naming and object definition (on both of which LF was progressively impaired, as expected for a diagnosis of SD), plus verbal and non-verbal 'non-semantic' tasks of reading aloud, spelling, object and lexical decision, and delayed copy drawing. Initially, his only striking 'non-semantic' deficit was in the domain of spelling - a pronounced surface dysgraphia in an individual with demonstrably superior pre-morbid spelling skill. Over time, and in line with his declining semantic system, LF's performance gradually deteriorated on all of the 'non-semantic' tasks. The most vulnerable items on most tasks were those with low frequency and an atypical form. This report adds to the growing body of evidence that a number of cognitive processes not usually considered to be 'semantic' in their demands rely on the integrity of semantic knowledge for successful execution. Furthermore, it provides the first indication that these non-semantic deficits might emerge in an order predictable from the typicality structure of the relevant domain.
... The disorder results in the loss of non-linguistic conceptual and lexical knowledge (Bozeat, Lambon Ralph, Patterson, Garrard, & Hodges, 2000), with spared motor, syntactic and phonological abilities (Graham, Patterson, & Hodges, 1999). Patients with semantic dementia yield a pattern like that of AD patients: they have more trouble producing and recognizing irregular than regular and-ed-suffixed novel past tenses, and the degree of their impairment on irregulars correlates with their performance on an independent lexical memory task (Patterson, Lambon Ralph, Hodges, & McClelland, 2001). ...
The structure of the brain and the nature of evolution suggest that, despite its uniqueness, language likely depends on brain systems that also subserve other functions. The declarative/procedural (DP) model claims that the mental lexicon of memorized word-specific knowledge depends on the largely temporal-lobe substrates of declarative memory, which underlies the storage and use of knowledge of facts and events. The mental grammar, which subserves the rule-governed combination of lexical items into complex representations, depends on a distinct neural system. This system, which is composed of a network of specific frontal, basal-ganglia, parietal and cerebellar structures, underlies procedural memory, which supports the learning and execution of motor and cognitive skills, especially those involving sequences. The functions of the two brain systems, together with their anatomical, physiological and biochemical substrates, lead to specific claims and predictions regarding their roles in language. These predictions are compared with those of other neurocognitive models of language. Empirical evidence is presented from neuroimaging studies of normal language processing, and from developmental and adult-onset disorders. It is argued that this evidence supports the DP model. It is additionally proposed that "language" disorders, such as specific language impairment and non-fluent and fluent aphasia, may be profitably viewed as impairments primarily affecting one or the other brain system. Overall, the data suggest a new neurocognitive framework for the study of lexicon and grammar.
... This debate has taken a strongly neuropsychological turn over the past five years, with several results (Miozzo, 2003;Tyler et al., 2002a;Ullman et al., 1997) pointing to a dis- sociation of the underlying neural systems required for the production and perception of English regular and irregular inflected forms. Patients who typically have damage involv- ing the anterior inferior temporal lobe tend to show poorer performance on the irregulars compared to the regulars in elicitation and reading tasks, while deficits for the regu- lars are associated with damage to L inferior frontal cortex (LIFC) and underlying structures (Marslen-Wilson & Tyler, 1997Patterson, Lambon Ralph, Hodges, & McClelland, 2001;Tyler et al., 2002a;Ullman et al., 1997). This has been shown in a variety of neuropsychological studies prob- ing the comprehension and production of the regular and ir- regular past tense (Longworth, Marslen-Wilson, Randall, & Tyler, in press;Marslen-Wilson & Tyler, 1997;Tyler et al., 2002a; Ullman et al., 1997). ...
A prominent issue in cognitive neuroscience is whether language function is instantiated in the brain as a single undifferentiated process, or whether regions of relative specialisation can be demonstrated. The contrast between regular and irregular English verb inflection has been pivotal to this debate. Behavioural dissociations related to different lesion sites in brain-damaged patients suggest that processing regular and irregular past tenses involves different neural systems. Using event-related fMRI in a group of unimpaired young adults, we contrast processing of spoken regular and irregular past tense forms in a same-different judgement task, shown in earlier research with patients to engage left hemisphere language systems. An extensive fronto-temporal network, linking anterior cingulate (ACC), left inferior frontal cortex (LIFC) and bilateral superior temporal gyrus (STG), was preferentially activated for regularly inflected forms. Access to meaning from speech is supported by temporal cortex, but additional processing is required for forms that end in regular inflections, which differentially engage LIFC processes that support morpho-phonological segmentation and grammatical analysis.
... Unsurprisingly, our report of ILJ's impairments in these aspects of language processing does not constitute absolutely the first hint that these abilities might be compromised in SD. For example, (1) difficulty in producing inflectional morphology, specifically the past tense of irregular verbs in English, has been documented in a group of SD cases (Patterson et al., 2001), although a recent study has demonstrated normal morphological/semantic priming from both regular and irregular past-tense verbs to their stem forms (Tyler et al., 2004, JCN). ...
This article describes a 52-month longitudinal study of a patient, ILJ, whose semantic profile fits the criteria for a classical case of semantic dementia (SD). As in all such cases, it was the semantic aspects of receptive and expressive language processing--essentially vocabulary--that were most dramatically affected. The novel observation from this study is ILJ's performance on a comprehensive language examination. Results from this assessment, even early in the course of his disease, are compatible with the hypothesis that phonological, morphological and/or syntactic aspects of language processing may be disrupted by their interaction with degraded information from the semantic system.
... This phenomenon is observed across a whole range of tasks, including reading aloud (where patients will correctly pronounce typical words such as "new" but will read "sew" as "sue"), 84 spelling of spoken words (correct spelling of typical words like "stem" or "blink" but errors like "blood" spelled "blud" or "scissors" spelled "sizzers"), 85 and generation of the past tense forms of verbs (correct infl ection of typical verbs like "talk" as "talked" but typicalisation errors to irregular verbs; thus, the past tense of "drink" becomes "drinked" instead of "drank"). 86 This kind of typicalisation error has an equivalent in the object domain. For example, when a patient with SD was asked to copy a drawing of a peacock with the stimulus picture present, he showed good copying skills (fi gure 2). ...
Semantic dementia (SD), one of the main clinical variants of frontotemporal dementia, presents a unique combination of clinical and imaging abnormalities. We describe the epidemiological, cognitive, and radiological features of SD. The distinctive and consistent neuropsychological deficits in this disorder have had a major effect on current conceptions of the organisation of semantic memory and its links to episodic memory, language, and perceptual processes. Structural (MRI) and functional (fluorodeoxyglucose-PET) studies in SD emphasise the role of the temporopolar and perirhinal cortices. Unlike other frontotemporal dementia syndromes, the neuropathological findings in SD are fairly predictable: most patients have ubiquitin-positive, tau-negative neuronal inclusions.
p class="Default"> Abstract. The mastery of the irregular form of verbs in the past simple tense poses challenges to non-native learners of English all over the world. The objectives of this study were to identify the types of learners’ strategies useful for mastering the irregular verb inflection, to describe and evaluate them, and to establish why the English First Additional Language learners face difficulties in mastering those strategies. The study followed a quantitative research design. A questionnaire was used as an instrument for data collection from the respondents. Data were analysed using the Statistical Package for Social Sciences version 22 to ensure valid interpretations. Subsequent themes were placed in a table and a graph dealing with the inflection of irregular verbs. The target group of this study comprised 21 Grade 10 learners who were attending Dimani Secondary School in Limpopo Province, South Africa during the academic year 2021. From the data analysis, the initial study findings established that the respondents were incompetent in mastering the inflection of irregular verbs in the past simple tense when using the suppletion principle and the terminal consonants phoneme changes. The researchers used the grouping of common irregular verbs and the learning of irregular verbs in sentences strategies because learners were different and learned irregular verb inflection differently. Although it was previously found that learners could not understand the inflection of irregular verbs in the past simple tense, after having utilised these two strategies, the inflection of irregular verbs in the past simple tense improved with tremendous results.
Keywords: Inflection; irregular verbs; past simple tense; strategies </p
This study was designed to explore the nature of the anomia that is a defining feature of semantic demen-tia. Using a pool of 225 sets of picture naming data from 78 patients, we assessed the effects on naming accuracy of several characteristics of the target objects or their names: familiarity, frequency, age of acquisition and semantic domain (living/non-living). We also analysed the distribution of different error types according to the severity of the naming deficit. A particular focus of the study was the impact on naming of a previously unconsidered variable: the typicality of an object within its semantic category. This factor had a major influence both on naming success and on the proportions of different error types. Moreover, and increasingly so with declining naming accuracy, the patients' single-word incorrect responses were more typical than the target names. The observed effects of typicality sit well within models of semantic memory that represent concepts in terms of patterns of co-occurrence of constituent features. The results add to a growing body of evidence that, throughout the progressive deterioration of conceptual knowledge that characterises semantic dementia, both accuracy of performance and the nature of error responses are increasingly determined by the domain-specific aspects of typicality relevant to the task in question.
Wernicke (1900, as cited in G. H. Eggert, 1977) suggested that semantic knowledge arises from the interaction of perceptual representations of objects and words. The authors present a parallel distributed processing implementation of this theory, in which semantic representations emerge from mechanisms that acquire the mappings between visual representations of objects and their verbal descriptions. To test the theory, they trained the model to associate names, verbal descriptions, and visual representations of objects. When its inputs and outputs are constructed to capture aspects of structure apparent in attribute-norming experiments, the model provides an intuitive account of semantic task performance. The authors then used the model to understand the structure of impaired performance in patients with selective and progressive impairments of conceptual knowledge. Data from 4 well-known semantic tasks revealed consistent patterns that find a ready explanation in the model. The relationship between the model and related theories of semantic representation is discussed.
A psycholinguistic account of human communication must explain how linguistic inputs and outputs are structured to convey the speaker's intended meaning. The concept of a "mental lexicon" plays a key role in standard conceptions of this process, referring to the learned representations that mediate between the spoken utterance (or written text) and the interpretation computed by the listener or reader. The organisation of these representations needs to reflect, broadly speaking, two kinds of linguistic information being communicated: semantic information, about meanings in the world; and a wide range of syntactic information, specifying grammatical relations, tense, aspect, and so forth. These different kinds of linguistic information are associated with specific lexical entities-words and morphemes-which are assembled together, in different ways in different languages, to convey the necessary mix of semantic and syntactic cues to intended meaning as the speech input is heard over time (or as a written text is read). This article discusses morphological processes in language comprehension, focusing on inflectional morphology and derivational morphology. It also considers morphological decomposition and lexical representation.
This paper investigates the production of German plural nouns by two aphasic participants with non-fluent speech production. Experimental tasks included two production tasks: (1) picture naming of single and multiple objects, and (2) an elicitation task of singular and plural nouns. Materials were controlled for regularity and predictability of plural form, and for dominance of number, referring to the relative difference in word form frequency between a singular and its corresponding plural form. Both regularity and number dominance have been shown to affect plural noun production in both unimpaired and aphasic speakers, but the underlying functional origin of these effects is still a matter of debate. The results point to differences in the lexical representation and processing of regular and irregular German plural nouns. Thus, the data are in line with the dual mechanism account.
Dans ce chapitre, nous présentons une étude visant à examiner les habiletés lexicosémantiques et morphologiques de patients atteints de démence de type Alzheimer (DTA) à un stade léger à modéré. Un groupe de personnes atteintes de DTA et un groupe de sujets-contrôles appariés en âge ont été soumis à une batterie de tests :dénomination, appariement fonctionnel et flexion de verbes et de noms. L’hypothèse d’une dissociation entre les habiletés lexico-sémantiques et les habiletés morphologiques a été confirmée à deux niveaux. D’une part, les comparaisons avec les sujets-contrôles indiquent un déficit du traitement lexical et sémantique chez les patients tandis que les habiletés morphologiques, mesurées par la flexion de formes régulières, sont préservées. D’autre part, la dissociation entre les formes régulières et les formes irrégulières présentée par les patients dans d’autres langues s’observe également en français. Ainsi, les patients atteints de DTAprésentent une dissociation et, par rapport aux sujets contrôles, montrent un déficit pour le traitement des formes irrégulières. La tâche de traitement de formes irrégulières, qui permet de discriminer les patients des sujets-contrôles, pourrait donc contribuer au diagnostic de la DTA. Les performances déficitaires des patients DTA à une tâche non verbale d’appariement fonctionnel ont permis de confirmer que le déficit sémantique n’est pas lié à un déficit de la connaissance verbale. En conclusion, cette étude confirme la dégradation sémantique liée à la dégénérescence des régions temporales chez les patients atteints de DTA. Par ailleurs, l’absence de corrélation de la tâche de flexion de formes irrégulières avec la tâche d’appariement fonctionnel qui évalue les habiletés sémantiques, la corrélation de ces mêmes formes avec des épreuves exécutives et l’hétérogénéité du profil de la DTA à la faveur du traitement sémantique dans cette étude plaident en faveur du rôle des systèmes attentionnels dans le déficit observé.
It has been suggested that damage to anterior regions of the left hemisphere results in a dissociation in the perception and lexical activation of past-tense forms. Specifically, in a lexical-decision task in which past-tense primes immediately precede present-tense targets, such patients demonstrate significant priming for irregular verbs (spoke-speak), but, unlike control participants, fail to do so for regular verbs (looked-look). Here, this behavioral dissociation was first confirmed in a group of eleven patients with damage to the pars opercularis (BA 44) and pars triangularis (BA 45) of the left inferior frontal gyrus (i.e., Broca's area). Two conditions containing word-onset orthographic-phonological overlap (bead-bee, barge-bar) demonstrated that the disrupted regular-verb priming was accompanied by, and covaried with, disrupted ortho-phonological priming, regardless of whether prime stimuli contained the regular inflectional rhyme pattern. Further, the dissociation between impaired regular-verb and preserved irregular-verb priming was shown to be continuous rather than categorical; priming for weak-irregular verbs (spent-spend) was intermediate in size between that of regular verbs and strong verbs. Such continuous dissociations grounded in ortho-phonological relationships between present- and past-tense forms are predicted by single-system, connectionist approaches to inflectional morphology and not predicted by current dual-system, rule-based models. Event-related potential data demonstrated that N400 priming effects were intact for both regular and irregular verbs, suggesting that the absence of significant regular-verb priming in the response time data did not result from a disruption of lexical access, and may have stemmed instead from post-lexical events such as covert articulation, segmentation strategies, and/or cognitive control.
Background: The background to the study is the debate in relation to the English regular/irregular past tense forms.
Aims: The purpose of the investigation was the evaluation of the dual mechanism (DMT: Pinker, 1999; Marslen-Wilson & Tyler, 1997, 1998; Ullman, Corkin, Coppola, Hickok, Growdon, Koroshetz, et al., 1997) and connectionist single mechanism models (SMT: Bird, Lambon Ralph, Seidenberg, McClelland, & Patterson, 2003; Joanisse & Seidenberg, 1999; Patterson, Lambon Ralph, Hodges, & McClelland, 2001) through exploring the reading and oral production of regular and irregular past tense forms and other verbal and nominal inflections by a Broca's type aphasic and phonological dyslexic patient.
Methods & procedures: Eight experimental tasks are reported. Three involved the reading of stems and inflected verbs and nouns in differently organised lists, two involved the oral production of past tense verbs and plural nouns, and three explored the ability to distinguish between written verbs inflected with various affixes.
Outcomes & results: In reading randomly organised list of nouns, verb stems, and regular and irregular past tense forms the patient displayed dissociation between regular and irregular past tense forms as predicted by DMT. When the same items were presented in a list with present and past tense forms paired, and in the oral transformation task, the dissociation disappeared, and performance in regular and irregular past tense forms became comparable. There was a difference in the patient's reading of plural nouns and progressive verbs, which was good, and of past tense forms and third person forms, which was impaired. The recognition/comprehension tasks revealed that the patient was aware of the presence of an affix, but he could not reliably distinguish between different affixes.
Conclusions: Performance on regular/irregular past tense forms and the variable levels of performance in producing different regular inflections are in conflict with both DMT and SMT on a number of grounds. The task-related differences between randomly organised lists and paired present and past tense forms are accounted for by distinguishing between morpho-phonological and morpho-syntactic effects. It is argued that deficits confined to the production of regular past tense forms are morpho-phonological in nature, while deficits in both regular and irregular past tense forms originate in morpho-syntax. Since SMT and DMT are theories of morpho-phonological processes, they cannot account for the complex performance pattern presented by the patient in the present study and by other similar patients. The differences attested in the availability of differently affixed words and deficits in irregular past tense forms are only accountable at the level of morpho-syntax.
Are words read visually (by means of a direct mapping from orthography to semantics) or phonologically (by mapping from orthography to phonology to semantics)? The authors addressed this long-standing debate by examining how a large-scale computational model based on connectionist principles would solve the problem and comparing the model's performance to people's. In contrast to previous models, the present model uses an architecture in which meanings are jointly determined by the 2 components, with the division of labor between them affected by the nature of the mappings between codes. The model is consistent with a variety of behavioral phenomena, including the results of studies of homophones and pseudohomophones thought to support other theories, and illustrates how efficient processing can be achieved using multiple simultaneous constraints.
The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects.
In semantic dementia (SD), there is a correlation between performance on semantic tasks such as picture naming and lexical tasks such as reading aloud. However, there have been a few case reports of patients with spared reading despite profound semantic impairment. These reports have sparked an ongoing debate about how the brain processes conceptual versus lexical knowledge. One possibility is that there are two functionally distinct systems in the brain-one for semantic and one for lexical processing. Alternatively, there may be a single system involved in both. We present a computational investigation of the role of individual differences in explaining the relationship between naming and reading performance in five SD patients, among whom there are cases of both association and dissociation of deficits. We used a connectionist model where information from different modalities feeds into a single integrative layer. Our simulations successfully produced the overall relationship between reading and naming seen in SD and provided multiple fits for both association and dissociation data, suggesting that a single, cross-modal, integrative system is sufficient for both semantic and lexical tasks and that individual differences among patients are essential in accounting for variability in performance.
We assessed spelling and reading abilities in 14 patients with semantic dementia (with varying degrees of semantic impairment) and 24 matched controls, using spelling-to-dictation and single-word reading tests which manipulated regularity of the correspondences between spelling and sound, and word frequency. All of the patients exhibited spelling and reading de®cits, except at the very earliest stages of disease. Longitudinal study of seven of the patients revealed further deterioration in spelling, reading, and semantic memory. The performance of both subject groups on both spelling and reading was aected by regularity and word frequency, but these eects were substantially larger for the patients. Spelling of words with exceptional (or more precisely, unpredictable) sound-to-spelling correspondences was most impaired, and the majority of errors were phonologically plausible renderings of the target words. Reading of low frequency words with exceptional spelling-to-sound correspondences was also signi®cantly impaired. The spelling and reading de®cits were correlated with, and in our interpretation are attributed to, the semantic impairment. #
The clinical presentation of patients with semantic dementia is dominated by anomia and poor verbal comprehension. Although a number of researchers have argued that these patients have impaired comprehension of non-verbal as well as verbal stimuli, the evidence for semantic deterioration is mainly derived from tasks that include some form of verbal input or output. Few studies have investigated semantic impairment using entirely non-verbal assessments and the few exceptions have been based on results from single cases ([3]: Breedin SD, Saffran EM, Coslett HB. Reversal of the concreteness effect in a patient with semantic dementia. Cognitive Neuropsychology 1994;11:617–660, [12]: Graham KS, Becker JT, Patterson K, Hodges JR. Lost for words: a case of primary progressive aphasia? In: Parkin A, editor. Case studies in the neuropsychology of memory, East Sussex: Lawrence Erlbaum, 1997. pp. 83–110, [21]: Lambon Ralph MA, Howard D. Gogi aphasia or semantic dementia? Simulating and assessing poor verbal comprehension in a case of progressive fluent aphasia. Cognitive Neuropsychology, (in-press).
Presents a standardized set of 260 pictures for use in experiments investigating differences and similarities in the processing of pictures and words. The pictures are black-and-white line drawings executed according to a set of rules that provide consistency of pictorial representation. They have been standardized on 4 variables of central relevance to memory and cognitive processing: name agreement, image agreement, familiarity, and visual complexity. The intercorrelations among the 4 measures were low, suggesting that they are indices of different attributes of the pictures. The concepts were selected to provide exemplars from several widely studied semantic categories. Sources of naming variance, and mean familiarity and complexity of the exemplars, differed significantly across the set of categories investigated. The potential significance of each of the normative variables to a number of semantic and episodic memory tasks is discussed. (34 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).
Language comprises a lexicon for storing words and a grammar for generating rule-governed forms. Evidence is presented that the lexicon is part of a temporal-parietalhnedial-temporal "declarative memory" system and that granlmatical rules are processed by a frontamasal-ganglia "procedural" system. Patients produced past tenses of regular and novel verbs (looked and plagged), which require an -ed-suffixation rule, and irregular verbs (dug), which are retrieved from memory. Word-finding difficulties in posterior aphasia, and the general declarative memory impairment in Alzheimer's disease, led to more errors with irregular than regular and novel verbs. Grammatical difficulties in anterior aphasia, and the general impairment of procedures in Parkinson's disease, led to the opposite pattern. In contrast to the Parkinson's patients, who showed sup pressed motor activity and rule use, Huntington's disease patients showed excess motor activity and rule use, underscoring a role for the basal ganglia in grammatical processing.
Connectionist accounts of inflectional morphology have focused on the domain of the English past tense in which the default process (add/ed/) reflects the process of suffixation adopted by the majority of forms in the language. Connectionist models exploit the imbalance between English regular and irregular verbs when learning the past tense and when responding to novel forms in a default fashion. Not all inflectional systems have a default which is characterised by a majority of forms in the language. The Arabic plural system has been cited as one such system where a minority default process operates-the "sound" plural in Arabic applies to only a minority of the forms in the lexicon, yet it appears to adopt the role of a default for novel nouns. We contrast two types of default process that might lead to this behaviour, a symbolic default and a distributional default. We provide a detailed analysis of the phonological similarity structure of the Arabic plural system and conclude that it is unlikely the distribution of singular Arabic nouns can support a distributional default for the sound plural. Nevertheless, classification networks and pattern association networks perform surprisingly well at the task of learning the Arabic plural and generalising to unseen Arabic nouns. In fact, the performance of a neural network classifier exceeds the performance of a symbolic hybrid "rule-associative" model even when the latter is optimised for correct classification. We conclude that the default rule is redundant, since generalisation to novel forms is more accurately predicted by the similarity structure in the phonological space of Arabic nouns alone. Finally, we present a set of empirical predictions for children's; acquisition of the Arabic plural system, derived from the network simulations.
Presents case reports of a 67-yr-old man and 2 women (aged 60 and 66 yrs) with primary cerebral atrophy in whom progressive breakdown in language and visual perception are attributed to loss of semantic information. This form of dementia is distinct from that of Alzheimer's disease and is assumed to represent a form of circumscribed cerebral atrophy with emphasis of pathology in temporal rather than frontal regions of the brain. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Describes a model in which perception results from excitatory and
inhibitory interactions of detectors for visual features, letters,
and words. A visual input excites detectors for visual features in
the display and for letters consistent with the active features.
Letter detectors in turn excite detectors for consistent words. It
is suggested that active word detectors mutually inhibit each other
and send feedback to the letter level, strengthening activation and
hence perceptibility of their constituent letters. Computer simulation
of the model exhibits the perceptual advantage for letters in words
over unrelated contexts and is considered consistent with basic facts
about word advantage. Most important, the model produces facilitation
for letters in pronounceable pseudowords as well as words. Pseudowords
activate detectors for words that are consistent with most active
letters, and feedback from the activated words strengthens activations
of the letters in the pseudoword. The model thus accounts for apparently
rule-governed performance without any actual rules. (50 ref) (PsycINFO
Database Record (c) 2007 APA, all rights reserved)
The significance of the English past tense in current cognitive science is that it offers a clear contrast between a potentially rule-based system-the procedures for forming the regular past tense-and an unpredictable and idiosyncratic set of irregular forms. This contrast has become a focus for a wide-ranging debate about whether mental computation requires the use of symbols. Highly regular combinatorial phenomena, such as the regular past tense, are prime candidates for rule-based symbolic computation. Earlier research concentrated on the evidence for this during language acquisition, looking at how children learned the English regular and irregular verb systems. Over the last five years attention has shifted towards the properties of the adult system, and we review here some recent research into the neural correlates of the two types of procedure. The evidence suggests that there are divergences in the neural systems underlying the generation and perception of regular and irregular forms. Regular inflected forms seem to involve primarily combinatorial processes, while irregular forms appear to have a hybrid status, sharing their semantic properties with the regular forms but diverging in the phonological domain, where their form representations are stored as complete units. This indicates that the regular and irregular past tenses may not, after all, provide a clean contrast in the types of mental computation they implicate.
We report five patients with a stereotyped clinical syndrome characterized by fluent dysphasia with severe anomia, reduced vocabulary and prominent impairment of single-word comprehension, progressing to a stage of virtually complete dissolution of the semantic components of language. A marked reduction in the ability to generate exemplars from restricted semantic categories (e.g. animals, vehicles, etc.) was a consistent and early feature. Tests of semantic memory demonstrated a radically impoverished knowledge about a range of living and man-made items. In contrast, phonology and grammar of spoken language were largely preserved, as was comprehension of complex syntactic commands. Reading showed a pattern of surface dyslexia. Autobiographical and day-to-day (episodic) memory were relatively retained. Non-verbal memory, perceptual and visuospatial abilities were also strikingly preserved. In some cases, behavioural and personality changes may supervene; one patient developed features of the Kluver-Bucy Syndrome. Radiological investigations have shown marked focal temporal atrophy in all five patients, and functional imaging by single positron emission tomography and positron emission tomography (one case) have implicated the dominant temporal lobe in all five. In the older literature, such cases would have been subsumed under the rubric of Pick's disease. Others have been included in series with progressive aphasia. We propose the term semantic dementia, first coined by Snowden et al. (1989), to designate this clinical syndrome.
Language and cognition have been explained as the products of a homogeneous associative memory structure or alternatively,
of a set of genetically determined computational modules in which rules manipulate symbolic representations. Intensive study
of one phenomenon of English grammar and how it is processed and acquired suggest that both theories are partly right. Regular
verbs (walk-walked) are computed by a suffixation rule in a neural system for grammatical processing; irregular verbs (run-ran)
are retrieved from an associative memory.
A three-layer back-propagation network is used to implement a pattern association task in which four types of mapping are learned. These mappings, which are considered analogous to those which characterize the relationship between the stem and past tense forms of English verbs, include arbitrary mappings, identity mappings, vowel changes, and additions of a suffix. The degree of correspondence between parallel distributed processing (PDP) models which learn mappings of this sort (e.g., Rumelhart & McClelland, 1986, 1987) and children's acquisition of inflectional morphology has recently been at issue in discussions of the applicability of PDP models to the study of human cognition and language (Pinker & Mehler, 1989; Bever, in press). In this paper, we explore the capacity of a network to learn these types of mappings, focusing on three major issues. First, we compare the performance of a single-layered perceptron similar to the one used by Rumelhart and McClelland with a multi-layered perceptron. The results suggest that it is unlikely that a single-layered perceptron is capable of finding an adequate solution to the problem of mapping stems and past tense forms in input configurations that are sufficiently analogous to English. Second, we explore the input conditions which determine learning in these networks. Several factors that characterize linguistic input are investigated: (a) the nature of the mapping performed by the network (arbitrary, suffixation, identity, and vowel change); (b) the competition effects that arise when the task demands simultaneous learning of distinct mapping types; (c) the role of the type and token frequency of verb stems; and (d) the influence of phonological subregularities in the irregular verbs. Each of these factors is shown to have selective consequences on both successful and erroneous performance in the network. Third, we outline several types of systems which could result in U-shaped acquisition, and discuss the ways in which learning in multi-layered networks can be seen to capture several characteristics of U-shaped learning in children. In general, these models provide information about the role of input in determining the kinds of errors that a network will produce, including the conditions under which rule-like behavior and U-shaped learning will and will not emerge. The results from all simulations are discussed in light of behavioral data on children's acquisition of the past tense and the validity of drawing conclusions about the acquisition of language from models of this sort.
This paper examines three methodological issues concerning the measurement of semantic memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of semantic memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their semantic memory store without visual perceptual deficits.
The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of semantic memory. It was found that verbal fluency (generation of semantic category lists) was impaired due to two major constraints: deterioration of semantic memory store, and variable difficulties in semantic search. Verbal fluency, therefore, reflects semantic memory loss to some degree, but is not a direct test of semantic memory store in DAT. The second issue was whether semantic memory impairment in our patients conformed to the ‘semantic storage disorder’ syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether semantic cueing and semantic priming, are altered in a similar manner in DAT. It demonstrated that semantic cueing and semantic priming, using the same words whose concepts were degraded in semantic memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of semantic loss after brain damage.
A parallel distributed processing model of visual word recognition and pronunciation is described. The model consists of sets of orthographic and phonological units and an interlevel of hidden units. Weights on connections between units were modified during a training phase using the back-propagation learning algorithm. The model simulates many aspects of human performance, including (a) differences between words in terms of processing difficulty, (b) pronunciation of novel items, (c) differences between readers in terms of word recognition skill, (d) transitions from beginning to skilled reading, and (e) differences in performance on lexical decision and naming tasks. The model's behavior early in the learning phase corresponds to that of children acquiring word recognition skills. Training with a smaller number of hidden units produces output characteristic of many dyslexic readers. Naming is simulated without pronunciation rules, and lexical decisions are simulated without accessing word-level representations. The performance of the model is largely determined by three factors: the nature of the input, a significant fragment of written English; the learning rule, which encodes the implicit structure of the orthography in the weights on connections; and the architecture of the system, which influences the scope of what can be learned.
A patient, JL, with the syndrome of semantic dementia was assessed longitudinally over a two-year period. The data presented here address the controversy concerning the hierarchical organisation of semantic memory. On a range of category fluency tests, when first tested JL was just within the normal range on the broadest categories of animals and household items, but was virtually unable to produce any instances of specific categories such as breeds of dog or musical instruments. Longitudinal fluency data for the animal category demonstrate that while JL continued to produce the most prototypical responses (cat, dog, horse), other animal labels dropped out early from his vocabulary. On the picture-sorting tests from our semantic memory test battery, JL's discrimination between living things and man-made objects was preserved for a substantial time in conjunction with a marked decline in his sorting ability for more specific categories, particularly features or attributes (e.g. size, foreign-ness, or ferocity of animals).
A connectionist approach to processing in quasi-regular domains, as exemplified by English word reading, is developed. Networks using appropriately structured orthographic and phonological representations were trained to read both regular and exception words, and yet were also able to read pronounceable nonwords as well as skilled readers. A mathematical analysis of a simplified system clarifies the close relationship of word frequency and spelling-sound consistency in influencing naming latencies. These insights were verified in subsequent simulations, including an attractor network that accounted for latency data directly in its time to settle on a response. Further analyses of the ability of networks to reproduce data on acquired surface dyslexia support a view of the reading system that incorporates a graded division of labor between semantic and phonological processes, and contrasts in important ways with the standard dual-route account.
A fundamental issue in the study of cognition and the brain is the nature of mental computation. How far does this depend on internally represented systems of rules, expressed as strings of symbols with a syntax, as opposed to more distributed neural systems, operating subsymbolically and without syntax? The mental representation of the regular and irregular past tense of the English verb has become a crucial test case for this debate. Single-mechanism approaches argue that current multilayer connectionist networks can account for the learning and representation both of regular and of irregular forms. Dual-mechanism approaches, although accepting connectionist accounts for the irregular forms, argue that a symbolic, rule-based system is required to explain the properties of the regular past tense and, by extension, the properties of language and cognition in general. We show here that the regular and irregular past tense are supported by different neural systems, which can become dissociated by damage to the brain. This is evidence for functional and neurological distinctions in the types of mental computation that support these different aspects of linguistic and cognitive performance.
The development of reading skill and bases of developmental dyslexia were explored using connectionist models. Four issues were examined: the acquisition of phonological knowledge prior to reading, how this knowledge facilitates learning to read, phonological and nonphonological bases of dyslexia, and effects of literacy on phonological representation. Compared with simple feedforward networks, representing phonological knowledge in an attractor network yielded improved learning and generalization. Phonological and surface forms of developmental dyslexia, which are usually attributed to impairments in distinct lexical and nonlexical processing "routes," were derived from different types of damage to the network. The results provide a computationally explicit account of many aspects of reading acquisition using connectionist principles.
This is the third volume in the Vancouver Studies in Cognitive Science Series. It is based on a conference that was held in 1990, which was sponsored by the Cognitive Science Program and Linguistics Department of Simon Fraser University. Over the last decade, there has emerged a paradigm of cognitive modeling that has been hailed by many researchers as a radically new and promising approach to cognitive science. This new paradigm has come to be known by a number of names, including “connectionism”, "neural networks", and "parallel distributed processing", (or PDP). This method of computation attempts to model the neural processes that are thought to underlie cognitive functions in human beings. Unlike the digital computation methods used by AI researchers, connectionist models claim to approximate the kind of spontaneous, creative and somewhat unpredicatable behavior of human agents. However, over the last few years, a heated controversy has arisen over the extent to which connectionist models are able to provide successful explanations for higher cognitive processes. A central theme of this book reviews the adequacy of recent attempts to implement higher cognitive processes in connectionist networks.
The processes required for object naming were addressed in a study of patients with semantic dementia (a selective decline of semantic memory resulting from progressive temporal lobe atrophy) and in a computational model of single-word production. Although all patients with semantic dementia are impaired in both single-word production and comprehension, previous reports had indicated two different patterns: (a) a parallel decline in accuracy of naming and comprehension, with frequent semantic naming errors, suggesting a purely semantic basis for the anomia and (b) a dramatic progressive anomia without commensurate decline in comprehension, which might suggest a mainly postsemantic source of the anomia. Longitudinal data for 16 patients with semantic dementia reflected these two profiles, but with the following additional important specifications: (1) despite a few relatively extreme versions of one or other profile, the full set of cases formed a continuum in the extent of anomia for a given degree of degraded comprehension; (2) the degree of disparity between these two abilities was associated with relative asymmetry in laterality of atrophy: a parallel decline in the two measures characterized patients with greater right-than left-temporal atrophy, while disproportionate anomia occurred with a predominance of atrophy in the left-temporal lobe. In an implemented computational model of naming, semantic representations were distributed across simulated left-and right-temporal regions, but the semantic units on the left were more strongly connected to left-lateralized phonolo-gical representations. Asymmetric damage to semantic units reproduced the longitudinal patient profiles of naming relative to comprehension, plus additional characteristics of the patients' naming performance. On the basis of both the neuropsychological and computational evidence, we propose that semantic impairment alone can account for the full range of word production deficits described here. &
The cortical anatomy of 6 patients with semantic dementia (the temporal lobe variant of frontotemporal dementia) was contrasted with that of a group of age-matched normal subjects by using voxel-based morphometry, a technique that identifies changes in gray matter volume on a voxel-by-voxel basis. Among the circumscribed regions of neuronal loss, the left temporal pole (Brodmann area 38) was the most significantly and consistently affected region. Cortical atrophy in the left hemisphere also involved the inferolateral temporal lobe (Brodmann area 20/21) and fusiform gyrus. In addition, the right temporal pole (Brodmann area 38), the ventromedial frontal cortex (Brodmann area 11/32) bilaterally , and the amygdaloid complex were affected, but no significant atrophy was measured in the hippocampus, entorhi-nal, or caudal perirhinal cortex. The degree of semantic memory impairment across the 6 cases correlated significantly with the extent of atrophy of the left anterior temporal lobe but not with atrophy in the adjacent ventromedial frontal cortex. These results confirm that the anterior temporal lobe is critically involved in semantic processing, and dissociate its function from that of the adjacent frontal region. Mummery CJ, Patterson K, Price CJ, Ashburner J, Frackowiak RSJ, Hodges JR. A voxel-based morphometry study of semantic dementia: relationship between temporal lobe atrophy and semantic memory.
This study examines the impact of progressive degeneration of conceptual knowledge on the content words used in connected speech elicited using the Cookie Theft picture description (Goodglass & Kaplan, 1983). We began with an analysis of control subjects' descriptions with regard to word types and their frequency and imageability. Because the impairment of conceptual knowledge in semantic demen-tia is graded by concept familiarity, we created a model of a standardized normal Cookie Theft description that was then progressively degraded by the systematic removal of lower bands of word frequency. We drew two main predictions from this model: reduced availability of the lower bands of word frequency should result in (a) an apparent deficit for noun retrieval in relation to verb retrieval and (b) an apparent reverse imageability effect. Results from a longitudinal study, in which three patients with semantic dementia each described the Cookie Theft picture on three occasions during the progression of their disease, confirmed these predictions. An additional cross-sectional analysis, adding narratives from a larger number of cases, demonstrated that the decline in ability to produce suitable words for the picture description is closely related to the extent of semantic impairment as measured in tests of word comprehension and production. Both verbs and nouns are affected by the degradation of semantic memory; the fact that the impairment to noun production is manifested earlier and more catastrophically may be attributed to the relatively lower frequency of these terms. The authors thank the patients and the members of the MRC Cognition and Brain Sciences Unit Volunteer Panel for their participation in this study. We are also grateful to two anonymous reviewers for their helpful comments on an earlier version of this paper. The research was in part funded by an EPS study visit award to the first author and by an NIH grant to
Al~tract-To establish whether semantic memory is consistently impaired in patients with very mild dementia of Alzheimer's type (DAT), we assessed episodic and semantic memory in 52 patients with DAT who were divided into three subgroups according to dementia severity on the Mini-Mental State Examination (minimal >23, mild 17-23 and moderate < 17) and 24 matched controls. The minimal group showed impairment on the following semantic memory measures: category fluency, naming of line drawings, naming to verbal description, answering semantic feature questions and a non-verbal picture-picture matching task (the Pyramids and Palm Trees Test). The mild and moderate groups showed additional deficits on picture sorting and word-picture matching tests. Within the minimal and mild groups there was, however, considerable heterogeneity. While some patients showed a consistent impairment across all of the semantic memory tests, others were impaired only on a subset of these tests and a few even performed flawlessly. In contrast, all patients showed a profound deficit in episodic memory: delayed recall of new verbal and non-verbal material appears to be a particularly sensitive marker of early DAT. These data are in keeping with recent neuropathological studies demonstrating that the transentorhinal region is consistently involved at a very early stage. Lesions in this site cause a functional disconnection of the hippocampus, and hence a profound episodic memory disorder. The fact that many, but not all, patients with early disease also show impairment of semantic memory suggests that damage to the transentorhinal region is not sufficient to produce significant disruption of semantic memory. Such disruption reliably occurs, we hypothesize, only when the pathology extends to the temporal neocortex proper.
This paper describes a computerised database of psycholinguistic information. Semantic, syntactic, phonological and orthographic information about some or all of the 98,538 words in the database is accessible, by using a specially-written and very simple programming language. Word-association data are also included in the database. Some examples are given of the use of the database for selection of stimuli to be used in psycholinguistic experimentation or linguistic research. © 1981, The Experimental Psychology Society. All rights reserved.
The most productive class of strong verbs in English is that exemplified by the verb string/strung. Both historical and experimental evidence show that the class is phonologically defined. However, the members do not share a single set of phonological features. Rather, the class is organized around a prototypical member (in the sense of Rosch 1978), to which the other members stand in a family-resemblance relation (in the sense of Wittgenstein 1953). The defining attributes of the class include the final consonants as well as the initial consonants and consonant clusters, and to a lesser extent the vowel of the base verb. The organization of the formal aspects of linguistic units is shown to follow the same principles as the organization of the content of the linguistic units. The phonological shapes of verbs in morphological classes can be organized into natural categories, like other natural and cultural objects.
Theories about the representation and processing of regular and irregular past tense forms of verbs in English have disagreed as to whether they should be treated as a unified phenomenon (e.g. both rule-governed, or both generated by a connectionist net), or as two distinct types of linguistic entities (e.g. regulars formed by rules of the grammar, irregulars stored in lexical memory). In this article we present data from a positron emission tomographic study in which subjects were asked to produce the Fast tense forms of regular, irregular, and nonce stems. We find very different amounts and areas of cortical activation in the regular and irregular tasks, as well as significantly different reaction times in producing the past tenses. We interpret our findings as supporting the grammar/lexicon theories, and discuss the implications of our results for general linguistic theory.*
Describes the construction of a graded difficulty test of concrete and abstract word synonym comprehension. The standardization sample consisted of 184 volunteers (aged 16–77 yrs) representing a cross-section of the population. Percentile scores and scaled scores are presented for each section of the test. The test was validated in an experimental group of 65 with unilateral cerebral lesions in the left or right hemispheres. The greatest impairments were observed in Ss with left temporal lobe lesions. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Theories of language learnability have focused on “normal” language development, but there is a group of children, termed “specifically language-impaired,” for whom these theories are also appropriate. These children present an interesting learnability problem because they develop language slowly, the intermediate points in their development differ in certain respects from the usual developmental stages, and they do not always achieve the adult level of language functioning. In this article, specifically language-impaired children are treated as normal learners dealing with an input that is distorted in principled ways. When the children are viewed from this perspective, Pinker's (1984) theory can account for many of the features of their language.
We investigated six patients with progressive focal dementia or progressive aphasia, who showed impairments in knowledge of word meaning ranging from moderate to very severe. In all cases, a test of oral word reading demonstrated preserved reading of words with regular spelling-to-sound correspondences (e.g. MINT), but impaired reading of words with atypical correspondences (e.g. PINT). The level of success on these “exception” words was significantly related to word frequency, and the most common error was the assignment of a more typical spelling-sound correspondence. Various explanations are considered for this common association between loss of word meaning and a surface alexic pattern of reading performance.
In a recent issue of this journal, Pinker and Prince (1988) and Lachter and Bever (1988) presented detailed critiques of Rumelhart and McClelland's (1986) connectionist model of the child's learning of the phonological form of the English past tense. In order to address these criticisms, a new connectionist model was constructed using the back-propagation algorithm, a larger input corpus, a fuller paradigm, and a new phonological representation. This new implementation successfully addressed the criticisms of the phonological representation used by Rumelhart and McClelland. It did a much better job of learning the past tense using a fuller input set with realistic frequencies of occurrence. Ancillary simulations using the same network were able to deal with the homonymy problem and the generation of forms like “ated” from “ate”. The one feature not provided by the new model was a way of modeling early correct production of irregular forms. The success of the new model can be used to help clarify the extent to which the published critiques apply to a particular connectionist implementation as opposed to fundamental principles underlying the broader connectionist conceptualization.
To examine visuospatial impairment in a task that minimizes episodic memory demands in individuals with very mild or mild dementia of the Alzheimer type compared with a healthy control group.
Initial scores on the Visual Form Discrimination Test enrolled in longitudinal studies of dementia of the Alzheimer type and healthy aging.
Alzheimer's Disease Research Center at Washington University, St Louis, Mo.
Volunteer samples of 59 people (35 women and 24 men) with mild dementia of the Alzheimer type, 66 (39 women and 27 men) with mild dementia of the Alzheimer type, and 146 healthy nondemented individuals (90 women and 56 men) were recruited between 1988 and 1992. Ages ranged from 51 to 96 years. Persons with confounding medical, neurologic, or psychiatric disorders were excluded. Dementia severity was staged by means of the Clinical Dementia Rating.
Total number correct on the Visual Form Discrimination Test as well as the numbers of three types of errors: peripheral figure movement or rotation, major figure distortion, and major figure rotation.
Visuospatial deficit was apparent in very mild dementia of the Alzheimer type. Individuals with both very mild and mild dementia of the Alzheimer type made more errors involving peripheral figures and rotation of a major figure than did healthy, nondemented individuals.
The initial effects of Alzheimer's disease on cognitive function are more pervasive than just episodic memory failure.
This paper reports a study of the breakdown of semantic memory in the case of a subject with semantic dementia. The first experiment shows that the subject failed to comprehend words of low familiarity and word frequency, even though the spoken word forms were recognised as familiar. Experiments 2 and 3 showed (a) that the recall of word meanings in definition tasks did not vary with the generality of the word meaning (e.g. category, basic level, or subordinate property) but varied instead with the concept familiarity and frequency of the name; (b) that the ability to verify properties of basic-level objects was not affected by the ability to comprehend the property name, but depended instead on the degree of knowledge demonstrated for the object name in definition tasks; (c) that properties were frequently verified correctly when the object had been defined only to the superordinate level. It is argued that the results do not support the widely held view that, in general, specific information is lost first when semantic memory breaks down. The selective failure to recall specific information for some word meanings is discussed with reference to two theoretical accounts.
Over the past few decades, refined cognitive architectures with highly specific components have been proposed to explain apparently selective disorders of reading, resulting from brain disease or injury, in previously literate adults. Recent analysis of the more general linguistic and cognitive abilities supported by neural systems damaged in the various forms of alexia favours a rather different view of reading and the kinds of models sufficient to account for its acquisition, skilled performance and disruption.
The formation of the past tense of verbs in English has been the focus of the debate concerning connectionist vs. symbolic accounts of language. Brain-injured patients differ with respect to whether they are more impaired in generating irregular past tenses (TAKE-TOOK) or past tenses for nonce verbs (WUG-WUGGED). Such dissociations have been taken as evidence for distinct "rule" and "associative" memory systems in morphology and against the connectionist approach in which a single system is used for all forms. We describe a simulation model in which these impairments arise from damage to phonological or semantic information, which have different effects on generalization and irregular forms, respectively. The results provide an account of the bases of impairments in verb morphology and show that these impairments can be explained within connectionist models that do not use rules or a separate mechanism for exceptions.
The modularity of the sentence processor, or lack thereof, remains a much-debated issue in psycholinguistics. The authors present evidence from a semantically impaired patient (DM) that bears on this issue. As demonstrated elsewhere (S. D. Breedin, E. M. Saffran, & H. B. Coslett, 1994), DM suffered a significant loss of semantic knowledge. Here, the authors show that this impairment did not compromise DM's ability to process syntactic information. DM performed well on grammaticality judgment tasks and on sentence comprehension tasks that required the use of syntactic information for the assignment of thematic roles. The resistance of syntactic operations to semantic loss would seem to pose a challenge for models in which "the syntactic and conceptual aspects of processing are ... inextricably intertwined" (J. L. McClelland, M. St. John, & R. Taraban, 1989, p. 329).
Biological systems which inspire connectionist architecture are
based upon axonal point to point connections. As we attempt to engineer
ever larger analogues of these neural networks we are forced to
multiplex neural signals over time shared paths. This can alter the
timing of signal arrival which is critical in oscillatory networks and
leads to the bandwidth-synchrony dilemma. This paper further describes
the problem, especially for analog VLSI systems, and approaches under
consideration for the solution
Can a perceptual processing deficit explain the impairment of inflectional morphology in developmental dysphasia? A computational investigation
- J J Hoeffner
- J L Mcclleland
Hoeffner JJ, McClleland JL. Can a perceptual processing deficit
explain the impairment of inflectional morphology in developmental dysphasia? A computational investigation, In: Clark E
(editor), Proceedings of the 25th Annual Child Language Forum.
Stanford CA: Center for the Study of Language and Information, 1993: pp. 38 -49.
Pyramids and Palm Trees: A Test of Semantic Access from Pictures and Words
- D Howard
- K Patterson
Howard D, Patterson K. Pyramids and Palm Trees: A Test of
Semantic Access from Pictures and Words. Bury St Edmunds:
Thames Valley Test Company, 1992.
Semantic dementia: one window on the structure and organisation of semantic memory
- K Patterson
- J R Hodges
Patterson K, Hodges JR. Semantic dementia: one window on the
structure and organisation of semantic memory. In: Cermak L,
editor. Handbook of Neuropsychology: Memory Disorders. Amsterdam, London: Elsevier, 2000:289-309.
Words and Rules: The Ingredients of Language. London: Weidenfeld and Nicolson
- S Pinker
Pinker S. Words and Rules: The Ingredients of Language.
London: Weidenfeld and Nicolson, 1999.
Fronto-temporal Lobar Degeneration: Fronto-temporal Dementia, Progressive Aphasia, Semantic Dementia
- J S Snowden
- D Neary
- Dma Mann
Snowden JS, Neary D, Mann DMA. Fronto-temporal Lobar
Degeneration: Fronto-temporal Dementia, Progressive Aphasia,
Semantic Dementia. New York: Churchill Livingstone, 1996.
Neural correlates of lexicon and grammar: evidence from the production, reading and judgment of inflection in aphasia
- Mt Ullman
- R Izvorski
- T Love
- Yee E Swinney
- D Hickok
Ullman MT, Izvorski R, Love T, Yee E, Swinney D, Hickok G.
Neural correlates of lexicon and grammar: evidence from the
production, reading and judgment of inflection in aphasia, Brain
and Language, In press.