Verb deficits in Alzheimer's disease and agrammatism: implications for lexical organization

This study examined the nature of verb deficits in 14 individuals with probable Alzheimer's Disease (PrAD) and nine with agrammatic aphasia. Production was tested, controlling both semantic and syntactic features of verbs, using noun and verb naming, sentence completion, and narrative tasks. Noun and verb comprehension and a grammaticality judgment task also were administered. Results showed that while both PrAD and agrammatic subjects showed impaired verb naming, the syntactic features of verbs (i.e., argument structure) influenced agrammatic, but not Alzheimer's disease patients' verb production ability. That is, agrammatic patients showed progressively greater difficulty with verbs associated with more arguments, as has been shown in previous studies (e.g., Kim & Thompson, 2000; Thompson, 2003; Thompson, Lange, Schneider, & Shapiro, 1997), and suggest a syntactic basis for verb production deficits in agrammatism. Conversely, the semantic complexity of verbs affected PrAD, but not agrammatic, patients' performance, suggesting "bottom-up" breakdown in their verb lexicon, paralleling that of nouns, resulting from the degradation or loss of semantic features of verbs.     

Verb processing during sentence comprehension in aphasia

This study examines verb processing during on-line sentence comprehension in aphasia. We describe two experiments that explore whether a group of Broca's aphasics, who were agrammatic in comprehension as well as speech, a group of fluent aphasics, and a group of normal controls are sensitive to the argument structure arrangements of verbs. Subjects had to perform a complex secondary task both in the immediate vicinity of the verb and also at a point well past the verb while listening to sentences for meaning. Reaction times to this secondary task show that both normal controls and agrammatic Broca's aphasic subjects activate multiple argument structure possibilities for a verb in the vicinity of the verb, yet at a point downstream from the verb such effects disappear. These data suggest that the problems agrammatic subjects show with verbs in sentence comprehension, and the general lexical access deficit also recently claimed to be part of the agrammatics' problem, may not extend to the real-time processing of verbs and their arguments. Fluent aphasic subjects, on the other hand, do not show sensitivity to the argument structure properties of verbs, suggesting that these patients may have a semantic-like sentence processing deficit.     

句子结构与控制动词类型对题元角色指派的影响

扩展论元依存模型认为：语序固定语言的题元角色指派依赖论元的语序线索; 论元线索与动词论元表征不一致时, 题元角色再分析会产生额外的加工负荷。为检验该模型, 本研究采用眼动记录方法, 实验为2 (句子结构：居中、前置) × 2 (控制动词类型：主语控制、宾语控制)被试内设计。通过操纵句子结构, 考察汉语读者对语序线索的依赖性; 通过操纵控制动词类型, 考察汉语论元线索与动词论元表征的一致性对题元角色指派的影响。结果发现：(1)前置结构的句子在名词1、名词2和动词区域的阅读时间和回视次数多于居中结构的句子; (2)宾语控制动词条件在动词和动词后区域的第二遍阅读时间和总回视次数多于主语控制动词条件; (3)在居中结构中, 宾语控制动词条件在名词2和动词区域的阅读时间和回视次数多于主语控制动词条件; 在前置结构中, 宾语控制动词条件在动词后区域的阅读时间多于主语控制动词条件。结果支持扩展论元依存模型。     

The role of entrenchment in children’s and adults’ performance on grammaticality judgment tasks

Between the ages of 3 and 7 years, children have been observed to produce verb argument structure overgeneralization errors (e.g., Don’t giggle me; Bowerman, 1982, 1988; Pinker, 1989). A number of recent studies have begun to find evidence that the precise distributional properties of the input may provide an important part of the explanation for why children retreat from overgeneralization errors (Brooks & Tomasello, 1999; Brooks, Tomasello, Dodson, & Lewis, 1999). The current study evaluates the role of entrenchment (Braine & Brooks, 1995) in constraining argument structure overgeneralization errors using a grammaticality judgment task. The 5-year-olds, 8-year-olds, and adults were presented with examples of argument structure errors containing high and low frequency verbs matched for semantic class and asked to indicate whether, or the extent to which they found the sentences to be grammatical. The data show that across all groups, sentences with argument structure errors containing low frequency verbs were judged to be significantly more grammatical than those containing high frequency verbs. These findings provide further support for the entrenchment hypothesis and suggest that verb frequency plays an important and continuing role in determining a speaker’s choice of verb argument structure.     

Semantic weight and verb retrieval in aphasia

Individuals with agrammatic aphasia may have difficulty with verb production in comparison to nouns. Additionally, they may have greater difficulty producing verbs that have fewer semantic components (i.e., are semantically "light") compared to verbs that have greater semantic weight. A connectionist verb-production model proposed by Gordon and Dell (2003) learns through error correction to "divide the labor" between syntax and semantics. Verbs that are semantically heavier come to depend less on syntax and more on semantics. For lighter verbs, the reverse is true. We performed this study to clarify the role of semantic weight in aphasic verb production and to test the prediction from Gordon and Dell that a brain lesion that impairs the syntactic input to verb retrieval will impair lighter verbs more than heavier ones. Consistent with this prediction, we found that the decrement for lighter verbs was present in a group with agrammatic aphasia but not in a matched group without agrammatism.     

The role of animacy and thematic relationships in processing active English sentences: evidence from event-related potentials

Recent event-related potential studies report a P600 effect to incongruous verbs preceded by semantically associated inanimate noun-phrase (NP) arguments, e.g., "eat" in "At breakfast the eggs would eat...". This P600 effect may reflect the processing cost incurred when semantic-thematic relationships between critical verbs and their preceding NP argument(s) bias towards different interpretations to those dictated by their sentences' syntactic structures. We have termed such violations of alternative thematic roles, 'thematic role violations.' Semantic-thematic relationships are influenced both by semantic associations and by more basic semantic features, such as a noun's animacy. This study determined whether a P600 effect can be evoked by verbs whose thematic structures are violated by their preceding inanimate NP arguments, even in the absence of close semantic-associative relationships with these arguments or their preceding contexts. ERPs were measured to verbs under four conditions: (1) non-violated ("At breakfast the boys would eat..."); (2) preceded by introductory clauses and animate NPs that violated their pragmatic expectations but not their thematic structures ("At breakfast the boys would plant..."); (3) preceded by semantically related contexts but inanimate NPs that violated their thematic structures ("At breakfast the eggs would eat..."); (4) preceded by semantically unrelated contexts and inanimate NPs that also violated their thematic structures ("At breakfast the eggs would plant..."). Pragmatically non-thematic role violated verbs preceded by unrelated contexts and animate NPs evoked robust N400 effects and small P600 effects. Thematically violated verbs preceded by inanimate argument NPs evoked robust P600 effects but no N400 effects, regardless of whether these inanimate arguments or their preceding contexts were semantically related or unrelated to these verbs. These findings suggest that semantic-thematic relations, related to animacy constraints on verbs' arguments, are computed online and can immediately impact verb processing within active, English sentences.     

Sensitivity to inflectional morphology in agrammatism: investigation of a highly inflected language

We present the results of a study with six Serbo-Croatian-speaking agrammatic patients on a test of inflectional morphology in which subjects judged whether spoken sentences were grammatical or ungrammatical. Sensitivity to two kinds of syntactic features was investigated in these aphasic patients: (1) subcategorization rules for transitive verbs (which must be followed by a noun in the accusative case; intransitive verbs can be followed by nouns in other noun cases); (2) sensitivity to the inflectional morphology marking noun case. The test items consisted of three-word sentences (noun-verb-noun) in which verb transitivity and appropriateness of the case inflection of the following noun were manipulated. Results of the grammaticality judgment task show that both syntactic properties are preserved in these patients.     

动词论元结构复杂性加工的认知神经机制

动词论元结构复杂性表现在论元数量、论元范畴选择模式、题元角色指派模式和映射方式四个方面。大部分实证研究表明, 更多的论元数量、选择性论元范畴、选择性题元角色指派以及非典型映射, 使动词论元结构加工的认知神经机制更复杂。多论元加工功能脑区主要涉及左侧额下回和外侧裂周后部; 选择性论元范畴加工功能脑区主要涉及左侧额下回、额叶中后部、颞上回和颞叶中后部; 选择性题元角色指派加工功能脑区主要涉及外侧裂周后部、左侧额叶中后部和额下回; 非典型映射加工功能脑区主要涉及左侧额下回、颞上回、颞中回和颞叶后部。左侧额下回可能涉及初始句法加工、动词次范畴确定、句法移位和非宾格动词语义加工, 左侧额叶中后部可能涉及初始句法加工和动词次范畴确定, 左侧颞上回和颞叶中后部可能涉及表层句法加工和表层论元句法-语义整合, 外侧裂周后部可能涉及论元语义表征。动词论元结构加工过程和动词词汇特征表明, 复杂性某些方面存在交互作用。动词论元结构复杂性与加工难易的对应关系、复杂性加工难度层级和交互作用的认知神经机制以及汉语动词论元结构复杂性加工认知神经机制等议题, 有待进一步探讨。     

Verbal Integration: The Interaction of Participant Roles and Sentential Argument Structure

This paper explores the interaction between sentence level syntactic information and the semantic information that is carried with the verb during sentence comprehension. A cross-modal integration task was employed to examine whether the number of participant roles (thematic roles associated with the central meaning of the verb) causes an increase in processing load during integration of the verb into on-going sentence comprehension. The effect of preceding sentential structural information (varied with respect to the number of argument and/or adjunct NPs preceding the verb) was also manipulated. Independent of the structural information preceding the verb, verbs with two partici-pant roles were integrated into the sentence faster than verbs with three participant roles. This finding suggests that participant roles are stored with the representation of the verb and made immediately available during integration and comprehension. In addition, the syntactic distinction between arguments and adjuncts is also shown to play an immediate role in parsing and integration of language on-line.     

The word order problem in agrammatism : I. Comprehension

The results of a picture-pointing comprehension test show that agrammatic aphasics have difficulty understanding sentences in which the underlying semantic roles are marked by the order of noun phrases around a verbal element. Agrammatic patients performed poorly on reversible constructions involving spatial prepositions (e.g., “The square is above the circle”) and verbs (e.g., “The dancer applauds the clown”). These results have significance for the interpretation of the underlying disturbance in agrammatism—whether the deficit is syntactic or purely phonological.     

Verb Comprehension Deficits in Probable Alzheimer's Disease

Studies of lexical comprehension in probable Alzheimer's disease (pAD) have focused almost exclusively on nouns. In the following preliminary study, we examined whether lexical comprehension for verbs is also impaired in 25 pAD patients. The semantic meaning of motion verbs, cognition verbs, and perception verbs was assessed with a triadic comparison task. Structural meaning associated with these verbs was evaluated by asking the patients to judge the coherence of sentence frames that accept these verbs naturally or awkwardly. We found that pAD patients are significantly impaired at identifying semantic relations among verbs. pAD patients also encountered significantly more difficulty judging the coherence of sentences than control subjects. Correlation and regression analyses demonstrated that semantic characteristics of verbs are projected from the verbs' sentence frames in control subjects, but there was minimal evidence for such a structural–semantic relationship in pAD. We consider several possible explanations for our preliminary observations of an impairment that has consequences for processing both semantic and structural aspects of verb meaning.     

Semantic context influences memory for verbs more than memory for nouns

Three experiments revealed that memory for verbs is more dependent on semantic context than is memory for nouns. The participants in Experiment 1 were asked to remember either nouns or verbs from intransitive sentences. A recognition test included verbatim sentences, sentences with an old noun and a new verb, sentences with an old verb and a new noun, and entirely new sentences. Memory for verbs was significantly better when the verb was presented with the same noun at encoding and at retrieval. This contextual effect was much smaller for nouns. Experiments 2 and 3 replicated this effect and provided evidence that context effects reflect facilitation from bringing to mind the same meaning of a verb at encoding and at retrieval. Memory for verbs may be more dependent on semantic context because the meanings of verbs are more variable across semantic contexts than are the meanings of nouns.     

The comprehension of anomalous sentences: evidence from structural priming

We report three experiments investigating how people process anomalous sentences, in particular those in which the anomaly is associated with the verb. We contrast two accounts for the processing of such anomalous sentences: a syntactic account, in which the representations constructed for anomalous sentences are similar in nature to the ones constructed for well-formed sentences; and a semantic account, in which the representations constructed for anomalous sentences are erroneous, or altogether missing, and interpretation is achieved on the basis of semantic representations instead. To distinguish between these accounts, we used structural priming. First, we ruled out the possibility that anomaly per se influences the magnitude of the priming effect: Prime sentences with morphologically incorrect verbs produced similarly enhanced priming (lexical boost) to sentences with the same correct verbs (Exp. 1). Second, we found that prime sentences with a novel verb (Exp. 2) or a semantically and syntactically incongruent verb (Exp. 3) produced a priming effect, which was the same as that produced by well-formed sentences. In accord with the syntactic account, we conclude that the syntactic representations of anomalous sentences are similar to those constructed for well-formed sentences. Our results furthermore suggest that lexically-independent syntactic information is robust enough to produce well-formed syntactic representations during processing without requiring aid from lexically-based syntactic information.     

Thematic role properties of subjects and objects

This paper tests two claims about the thematic roles Agent and Patient: first, that they can be decomposed into more primitive features, as laid out in Dowty's (1991) Proto-Roles Hypothesis; and second, that these properties can be inferred directly from the grammatical roles subject and object. In Experiments 1 and 2, participants rated the Proto-Roles properties of the subject and object of transitive sentences with real verbs. Subjects were rated as more Agent-like than objects, while objects were rated as more Patient-like than subjects. Experiment 3 used transitive sentences with nonsense content words (e.g. "The rom mecked the zarg"). Even in the absence of a known verb, the results were the same. Experiment 4 examined the corollary prediction that subjects and objects should not differ on grammatically irrelevant properties (e.g. "being liquid"); this prediction was confirmed. In Experiment 5, verbs that do not permit objects (e.g. "fall," "erupt") were placed in the transitive frame. Results were the same as in Experiments 1 through 3. Moreover, the semantics of the verb were altered by the frame, indicating that participants tried to fuse the semantics of the verb with those of the frame. Possible sources of these inferences are considered.     

Syntactic frame and verb bias in aphasia: plausibility judgments of undergoer-subject sentences

This study investigates three factors that have been argued to define "canonical form" in sentence comprehension: Syntactic structure, semantic role, and frequency of usage. We first examine the claim that sentences containing unaccusative verbs present difficulties analogous to those of passive sentences. Using a plausibility judgment task, we show that a mixed group of aphasics performed significantly better on unaccusatives than on passives. We then turn to the observation that passives are generally harder than actives for aphasics. We show that this effect is modulated by lexical bias, i.e., the likelihood that a verb appears in a given syntactic structure: Passives of passive-bias verbs were significantly easier than passives of active-bias verbs. More generally, sentences whose structure matches the lexical bias of the main verb are significantly easier than sentences in which structure and lexical bias do not match. These findings suggest that "canonical form" reflects frequency and lexical biases.     

Agrammatic sentence production: is verb second impaired in Dutch?

This study investigates effects of verb movement in nine Dutch-speaking agrammatic aphasics. According to linguistic theory, in verb second languages such as Dutch and German, the verb remains in its clause-final base position in embedded clauses, whereas it moves to second position in main clauses. In recent linguistic accounts of agrammatic sentence production, it has been suggested that the production of sentences with moved verbs is relatively difficult. However, we argue that evidence provided by previous studies on this matter is inconclusive. An experiment is reported in which the production of both types of clauses is compared. No evidence is found that sentences with moved verbs are relatively difficult to produce. In fact, there was a tendency for the base order sentences to be harder. Implications of these findings for theories of normal and agrammatic sentence production are discussed.     

Patterns of comprehension and production of nouns and verbs in agrammatism: implications for lexical organization

This study examined the relationship between verb retrieval and verb-argument-structure properties in seven agrammatic aphasic patients using tasks requiring access to the verb's lexicon for both comprehension- and productionlike processes. Results showed intact comprehension of both nouns and verbs and noun naming, but impaired naming of verbs. Subjects also demonstrated near-normal performance on a grammaticality judgment task involving verb-argument-structure violations but were impaired in categorizing verbs by type (based on number of obligatory arguments). In both naming and categorization conditions, a hierarchy of verb difficulty emerged. Subjects were more accurate in naming/categorizing one-place verbs than two-place verbs and more accurate in naming/categorizing two-place verbs than three-place verbs. The pattern of selective impairment in lexical access/retrieval supports the hypothesis that one dimension of normal lexical organization is by form class. The results also suggest that no necessary relationship exists between production difficulties and comprehension of nouns/verbs in agrammatism. Further, the performance pattern noted supports the claim that verb-argument-structure properties, an important component of the verb lexicon, influence verb production at the single-word and at the sentence level. Subjects' performance on different tasks suggests that the locus of breakdown in the verb-retrieval processes for productionlike tasks may be in accessing information at the lemma level of representation as per Bock's model (1995) of sentence production.     

The time course of argument reactivation revealed: using the visual world paradigm

Previous research has found that the single argument of unaccusative verbs (such as fall) is reactivated during sentence processing, but the argument of agentive verbs (such as jump) is not (Bever & Sanz, 1997; Friedmann, Taranto, Shapiro, & Swinney, 2008). An open question so far was whether this difference in processing is caused by a difference in thematic roles the verbs assign, or a difference in the underlying syntactic structure. In the present study we tease apart these two potential sources. In order to achieve this, we included a set of verbs (like sparkle) which are equal to unaccusative verbs in the thematic role they assign to their argument, but equal to agentive verbs in the syntactic status of their argument (henceforth mixed verbs). As a method we used the visual world paradigm as this enables us to measure processing of the sentences continuously. This method also allowed us to test another hypothesis, namely the hypothesis that not only the argument of unaccusative verbs is reactivated during processing, but also the argument of agentive verbs. This reactivation is expected as the result of integrating the verb and its argument into one representation. In our experiment, participants listened to sentences including one of the three types of verbs. While listening, they viewed a visual display in which one of four objects was strongly related to the argument of the verb (wood-saw). The gaze record showed that the eyes moved to the related object (saw) upon presentation of the argument (wood). More interestingly, the eyes moved back to the related object upon presentation of the verb (fell). We found that looks to the related object increase only late after verb offset for unaccusative verbs, replicating the findings of previous research. We also found a rise in looks to the related object in agentive verbs, but this rise took place much earlier, starting slightly after verb onset. Finally, we found that mixed verbs pattern in processing with agentive verbs. We conclude that the argument of the verb is always reactivated, independent of verb type. In addition, the timing of integration differs per verb type and depends on the syntactic status of the argument and not on the thematic role that is assigned to the argument.     

Comprehending Noun Phrase Arguments and Adjuncts

Two experiments investigated how readers comprehend noun phrase (NP) arguments and adjuncts. Previous research suggested that argument phrases are processed more quickly than adjunct phrases (Clifton, Speer, & Abney, 1991; Kennison, 1999; Schütze & Gibson, 1999; Speer & Clifton, 1998). The present experiments investigated whether the type of verb in the sentence context could influence how NP arguments and adjuncts were processed. Reading time was measured on sentences containing NP arguments and adjuncts preceded either by verbs occurring most frequently with NP arguments (biased transitive verbs) or by verbs occurring most frequently without NP arguments (biased intransitive verbs) (e.g., Meredith read/performed every play/week.). In Experiment 1, reading time was measured using a self-paced phrase-by-phrase moving window. In Experiment 2, reading time was measured using eye tracking. The results of both experiments indicated that, following biased transitive verbs, NP arguments were processed more quickly than NP adjuncts. When NPs followed biased intransitive verbs, there was no significant difference between the processing time of NP arguments and adjuncts.