Verb retrieval in brain-damaged subjects: 1. Analysis of stimulus, lexical, and conceptual factors

Verb retrieval for action naming was assessed in 53 brain-damaged subjects by administering a standardized test with 100 items. The goal of the study was to gain further insight into the nature of verb processing impairments by investigating the influence of several kinds of stimulus, lexical, and conceptual factors on the subjects' performance at the level of group tendencies and also at the level of individual differences. (1) Stimulus factors: visual complexity, familiarity, image agreement, and one vs. two pictures (which corresponds to ongoing vs. completed actions); (2) lexical factors: name agreement, verb frequency, and whether the root of the target verb has a homophonous noun; (3) conceptual factors: whether the action is done with the hand or the body, whether the action involves one or two core participants, whether the undergoer of the action has a change of internal state, whether the undergoer has a change of spatial location, and whether the actor makes use of an instrument in carrying out the action. The subjects were divided into an impaired group (n = 19) and an unimpaired group (n = 34) on the basis of their overall performance on the test. For both groups of subjects, verb retrieval was significantly affected by the following factors: familiarity, image agreement, name agreement, homophonous noun, and undergoer change of location. These results indicate that, at the level of group analysis, some factors have a stronger influence on verb retrieval for action naming than others. Moreover, the finding that the two groups exhibited the same general pattern of factor sensitivity suggests that although the processing efficiency of the mechanisms that subserve verb retrieval is degraded in the impaired group, the basic functional properties of these mechanisms may not be qualitatively very different from those of the unimpaired group. Further analyses were conducted at the level of individual subjects and revealed a considerable amount of variation with regard to factor sensitivity. Many patterns of associations and dissociations of factors were found across the subjects, which suggests that the task of retrieving verbs for naming actions is quite complex and that different subjects can be influenced by different properties of both the stimuli and the target verbs.     

A selective deficit for living things after temporal lobectomy for relief of epileptic seizures.

Unilateral left and right temporal lobectomy patients and normal control subjects were tested on confrontation naming, speeded naming, category generation, and category and associate matching tasks. Both groups of patients were disproportionately impaired for living relative to nonliving things in confrontation naming, speeded naming, and category generation. We argue that damage to the temporal lobe impairs lexical retrieval most strongly for living things and that the anterior temporal cortices are convergence zones particularly necessary for retrieving the names of living things.     

Selective impairment of lexical stress assignment in an Italian-speaking aphasic patient

Psycholinguistic speech production models assume that lexical stress is stored and accessed separately during phonological encoding. We address the questions of the storage and computation of lexical stress in a case study of an Italian-speaking patient with an impairment of lexical stress assignment in naming, reading, and repeating single words. The patient's stress error pattern and his performance on tasks examining lexical stress in perception suggest an impairment in the retrieval of the stress pattern of irregular words. In contrast, his assignment of stress to nonstored phonological forms suggests that the computation of stress is unimpaired.     

Mechanisms for accessing lexical representations for output: evidence from a category-specific semantic deficit

We report the performance of a neurologically impaired patient, JJ, whose oral reading of words exceeded his naming and comprehension performance for the same words--a pattern of performance that has been previously presented as evidence for "direct, nonsemantic, lexical" routes to output in reading. However, detailed analyses of JJ's reading and comprehension revealed two results that do not follow directly from the "direct route" hypothesis: (1) He accurately read aloud all orthophonologically regular words and just those irregular words for which he demonstrated some comprehension (as indicated by correct responses or within-category semantic errors in naming and comprehension tasks); and (2) his reading errors on words that were not comprehended at all (but were recognized as words) were phonologically plausible (e.g., soot read as "suit"). We account for these results by proposing that preserved sublexical mechanisms for converting print to sound, together with partially preserved semantic information, serve to mediate the activation of representations in the phonological output lexicon in the task of reading aloud. We present similar arguments for postulating an interaction between sublexical mechanisms and lexical output components of the spelling process.     

Semantic abilities in dementia of the Alzheimer type. 1. Lexical semantics

The lexical semantic abilities of 18 Alzheimer patients were investigated using confrontation naming tasks (including both visual and tactile naming tests) and compared to those of a group of institutionalized, nonneurologically impaired control subjects matched for age, sex, and educational level. The Alzheimer patients produced a greater number of naming errors than the control subjects. The errors made by subjects during the naming tasks were analyzed according to a set of 16 error response types. The Alzheimer patients' response patterns suggest that they do recognize objects which they are unable to name and are able to identify the semantic class to which the target belongs, but cannot provide the lexeme corresponding to the correct individual class member. The results support a semantic network disruption rather than a visual perceptual deficit as the basis of the naming disturbance observed in Alzheimer patients.     

Formal paraphasias: A single case study

A case study is reported of an aphasic patient, RB, who showed frequent form-related whole-word substitutions in oral naming, writing to dictation, and reading aloud. In both written language tasks, the abstractness of the targets influenced the number of formal errors. In oral naming, a high proportion of formal paraphasias was related to the intended words in both form and meaning. A comparison between targets and formal paraphasias indicated a high agreement both in word class, number of syllables, stress pattern, and in basic (stressed) vowels. The agreement in consonants (including word-initial consonants), however, was low. It is argued that RB's formal substitutions are not caused solely by errors of lexical selection but that semantic, lexical, and segmental factors contribute to the error outcome.     

Contribution of perceptual and lexical-semantic errors to the naming impairments in Alzheimer's disease

The contribution of perceptual and semantic processing deficits to naming-test performance by Alzheimer's Disease subjects was examined. Groups of 34 Alzheimer subjects and 25 elderly controls completed tests of naming standard line drawings and naming perceptually degraded figures, and a test of verbal fluency for a specific semantic category. Alzheimer subjects were impaired on all measures and, when their naming-test errors were analyzed, they showed higher proportions of perceptual errors and failures to respond. Further, considerable variability in the proportions of different types of error was found both among subjects and among test items. These findings indicate that poor naming-test performance cannot necessarily be attributed to a specific deficit in semantic processing. Also, the discrepancies between previous reports of the naming deficits in Alzheimer's Disease may reflect differences in task difficulty and item selection that were apparent in this study.     

语义相似性与类别大小对图-词干扰范式下语义效应的影响

采用基本水平命名和类别水平命名任务, 通过2个实验, 考察了图-词之间的语义相似性与类别大小对图-词干扰范式下语义效应的影响。实验1发现, 图片命名时间在语义相似性高的干扰词条件下显著快于在语义相似性低的干扰词条件下, 但这种效应只出现在基本水平命名任务中, 未出现在类别水平命名任务中。图-词之间的语义相似性高低对低熟悉图片命名影响大, 对高熟悉图片命名影响小。实验2显示, 语义关联的干扰词对图片的基本水平命名产生了语义干扰效应, 对图片的类别水平命名产生了语义促进效应。类别大小强化了语义效应：类别大, 图片的基本水平命名的语义干扰效应更大, 图片的类别水平命名的语义促进效应更强。整个研究表明, 图-词之间的语义关联的强度影响语义效应的方向, 图-词之间的语义关联的广度影响语义效应的强弱。需要结合多种理论来解释图-词之间的语义相似性和类别大小对图-词干扰范式下语义效应的影响。     

Evidence for separate tonal and segmental tiers in the lexical specification of words: a case study of a brain-damaged Chinese speaker

We present an acoustic study of segmental and prosodic properties of words produced by a female speaker of Chinese with left-hemisphere brain damage. We measured the location of the point vowels /a, e, [Symbol: see text], i, y, o, u/ and determined their separation in the vowel plane, and their perceptual distinctivity. Similarly, the acoustic properties of the four lexical tones were measured in the F0 x time space. The data for our brain-damaged speaker were compared with those of a healthy control speaker. Results show that the patient's vowels hardly suffered from her lesion (relative to the vowel dispersion in the healthy control speaker), but that the identifiability of the four lexical tones was greatly compromised. These findings show that the tonal errors in aphasic speech behave independently of the segmental errors, even though both serve to maintain lexical contrasts in Chinese, and are therefore part of the lexical specification of Chinese words. The present study suggests that the specification of segmental and tonal aspects of lexical entries in Chinese, and in tone languages in general, are located or processed separately in the brain.     

Frequency effects with visual words and syllables in a dyslexic reader

The present study investigated the nature of the inhibitory syllable frequency effect, recently reported for normal readers, in a German-speaking dyslexic patient. The reading impairment was characterized as a severe deficit in naming single letters or words in the presence of spared lexical processing of visual word forms. Three visual lexical decision experiments were conducted with the dyslexic patient, an unimpaired control person matched to the patient and a control group: Experiment 1 manipulated the frequency of words and word-initial syllables and demonstrated systematic effects of both factors in normal readers and in the dyslexic patient. The syllable frequency effect was replicated in a second experiment with a more strictly controlled stimulus set. Experiment 3 confirmed the patient's deficit in activating phonological forms from written words by demonstrating that a pseudohomophone effect as observed in the unimpaired control participants was absent in the dyslexic patient.     

The processing of lexical stress during visual word recognition: typicality effects and orthographic correlates

Many studies that have examined reading at the single-word level have been restricted to the processing of monosyllabic stimuli, and, as a result, lexical stress has not been widely investigated. In the experiments reported here, we used disyllabic words and nonwords to investigate the processing of lexical stress during visual word recognition. In Experiments 1 and 2, we found an effect of stress typicality in naming and lexical decision. Typically stressed words (trochaic nouns and iambic verbs) elicited fewer errors than atypically stressed words (iambic nouns and trochaic verbs). In Experiment 3, we carried out an analysis of 340 word endings and found clear orthographic correlates of both grammatical category and lexical stress in word endings. In Experiment 4, we demonstrated that readers are sensitive to these cues in their processing of nonwords during two tasks: sentence construction and stress assignment. We discuss the implications of these findings with regard to psycholinguistic models of single-word reading.     

The processing of lexical stress during visual word recognition: Typicality effects and orthographic correlates

Many studies that have examined reading at the single-word level have been restricted to the processing of monosyllabic stimuli, and, as a result, lexical stress has not been widely investigated. In the experiments reported here, we used disyllabic words and nonwords to investigate the processing of lexical stress during visual word recognition. In Experiments 1 and 2, we found an effect of stress typicality in naming and lexical decision. Typically stressed words (trochaic nouns and iambic verbs) elicited fewer errors than atypically stressed words (iambic nouns and trochaic verbs). In Experiment 3, we carried out an analysis of 340 word endings and found clear orthographic correlates of both grammatical category and lexical stress in word endings. In Experiment 4, we demonstrated that readers are sensitive to these cues in their processing of nonwords during two tasks: sentence construction and stress assignment. We discuss the implications of these findings with regard to psycholinguistic models of single-word reading.     

A diffusion model account of normal and impaired readers

Acquired aphasics and dyslexics with even very profound word reading impairments have been shown to perform relatively well on the lexical decision task, but direct contrasts with unimpaired participant's data is often complicated by extremely long reaction times for patient data. The dissociation between lexical decision and word naming performance shown by these patients is of theoretical importance, and here we present an analysis of processing underlying the lexical decision task. We are able to determine what aspects of performance are affected by acquired aphasics in the lexical decision task. We fit lexical decision data from aphasic patients and from normal readers with a sequential sampling model (the diffusion model) that simultaneously considers reaction time and accuracy. This model provides a powerful means of assessing processes involved in impaired and unimpaired lexical decision. Our results suggest that lexical decision may tap impairments at both a linguistic and a nonlinguistic level. These impairments combine to make patients produce the exaggerated lexical decision reaction times typical of neurolinguistic patients: we demonstrate that patients have compromised decision and nondecision processes but that the quality of the information upon which they base their decisions is not much different from that of unimpaired participants.     

Accurate reading by nonlexical means: A case study

Accurate reading of irregular words is generally assumed to require intact lexical reading mechanisms. A nonlexical mechanism is usually deemed insufficient for this type of stimulus processing. The maximum level of accuracy attainable by nonlexical means, however, has not been adequately evaluated. We now describe a patient with acquired dyslexia due to impaired lexical reading mechanisms who retained the ability to read irregular words. The patient's poor performance on tasks requiring lexical decision and access to word meaning provided evidence that his lexical mechanisms were impaired. Nevertheless, errors on irregular words became apparent only with special tests that circumvented the patient's ability to use his intact speaking vocabulary to ensure that reading responses were words. The results demonstrate that relatively accurate reading of irregular words is possible despite damage to lexical mechanisms and that this can be achieved by filtering potential responses through the speaking vocabulary.     

Contextual control over lexical and sublexical routines when reading English aloud

Are the processes responsible for reading aloud single well-formed letter strings under contextual control? Despite the widespread contention that the answer to this question is “yes,” it has been remarkably difficult to provide a compelling demonstration to that effect. In a speeded naming experiment, skilled readers read aloud exception words (such asPint) that are atypical in terms of their spelling sound correspondences and nonwords (such asFlad) that appeared in a predictable sequence. Subjects took longer to name both words and nonwords when the item on the preceding trial was from the other lexical category, relative to when the preceding item was from the same lexical category. This finding is consistent with the relative contributions of lexical and sublexical knowledge being controlled. We note a number of different ways that this control could arise and suggest some directions for future research.     

Lexical retrieval in left and right brain lesioned children

Performance on two measures of lexical retrieval for 19 left and 13 right brain lesioned children was compared to that of control subjects matched by age, sex, race, and social class. On the Word-Finding Test, left lesioned subjects were significantly slower in response time than left controls when given semantic and visual cues and made more errors when given rhyming cues. On the Rapid Automatized Naming Test, left lesioned subjects were significantly slower than left controls in naming all semantic categories, including colors, numbers, objects, and letters. In contrast, right lesioned subjects responded as quickly as or more quickly than did right controls in all access conditions and in naming semantic categories yet tended to produce more errors than their controls, suggesting a speed-accuracy tradeoff. Children sustaining left brain lesions before 1 year of age appeared to be as impaired as those whose lesions occurred after 1 year of age. Diverse lesion sites within the left hemisphere were associated with increased lexical retrieval latencies.     

Visual field differences in verbal tasks: Effects of task familiarity and sex of subject

Four experiments using normal subjects investigated differences in magnitude of the right visual field (RVF) superiority as a function of word material (frequency and concreteness/imageability status), nonword letter strings (some of which were homophonic with nonpresented real words), and type of task (overt naming or lexical decision with discriminatory manual responses) as well as sex of the subject and the subject's familiarity with the material. Both latency and error measures showed that RVF superiority was more consistent when overt naming was required and with male subjects. For female subjects engaged in lexical decisions, a left visual field (LVF) superiority was often apparent, especially in the first half of an experimental sequence; when actually naming the items aloud, they showed field asymmetries similar to males. Except from an analysis of errors, there was little evidence to support differential right hemisphere mediation of high frequency concrete/imageable materials. It is suggested that in females, right hemisphere space normally reserved for visuospatial processing may have been invaded by secondary speech mechanisms. These mechanisms appear to operate at an essentially lexical level and may act in a supportive or auxiliary capacity for difficult or unfamiliar material; they seem to be equally concerned with both phonological and graphological processing and may account for the well-known female superiority in verbal tasks and inferiority in visuospatial tasks. Other findings are discussed such as the degree of consistency of the field differences, both for the same subjects and for the same stimulus materials under different task requirements and experimental conditions.     

Lexical characteristics of words used in emotional Stroop experiments

Validity of the emotional Stroop task hinges on equivalence between the emotion and the control words in terms of lexical features related to word recognition. The authors evaluated the lexical features of 1,033 words used in 32 published emotional Stroop studies. Emotion words were significantly lower in frequency of use, longer in length, and had smaller orthographic neighborhoods than words used as controls. These lexical features contribute to slower word recognition and hence are likely to contribute to delayed latencies in color naming. The often-replicated slowdown in color naming of emotion words may be due, in part, to lexical differences between the emotion and control words used in the majority of such studies to date.     

Word production and comprehension in Alzheimer's diseáse: The breakdown of semantic knowledge

Relatively mildly impaired patients with suspected Alzheimer's disease (N = 14; Verbal IQ = 96) and normal controls of similar age and education (N = 11) were administered tests requiring production (naming and fluency) and comprehension of single words. Word comprehension was assessed on a superordinate level (rating words for degree of “pleasantness”) and on a more specific level (matching abstract pictorial representations with printed words denoting objects, actions, emotions, and modifiers). Performance on standardized measures of semantic knowledge (Vocabulary and Similarities subtests of the WAIS) was also evaluated. The naming and fluency abilities of the Alzheimer's patients were found to be highly correlated (r = .80) and impaired. Naming errors often consisted of semantic field errors which were either hierarchically or linearly related to the target name. In comparison with normals, verbal fluency was characterized by a tendency to generate proportionally more category names concurrent with reduced production of items within a category. Single-word comprehension was also impaired, except when judgments of affective meaning were required. It was argued that these results suggest that Alzheimer's disease may lead to a specific disruption in semantic knowledge characterized by a difficulty in differentiating between items within the same semantic category concurrent with the relative preservation of broader categorical information.