Lexical access in aphasic and nonaphasic speakers

Representing the meanings of object and action words: The featural and unitary semantic space hypothesis

This paper presents the Featural and Unitary Semantic Space (FUSS) hypothesis of the meanings of object and action words. The hypothesis, implemented in a statistical model, is based on the following assumptions: First, it is assumed that the meanings of words are grounded in conceptual featural representations, some of which are organized according to modality. Second, it is assumed that conceptual featural representations are bound into lexico-semantic representations that provide an interface between conceptual knowledge and other linguistic information (syntax and phonology). Finally, the FUSS model employs the same principles and tools for objects and actions, modeling both domains in a single semantic space. We assess the plausibility of the model by showing that it can capture generalizations presented in the literature, in particular those related to category-related deficits, and show that it can predict semantic effects in behavioral experiments for object and action words better than other models such as Latent Semantic Analysis (Landauer & Dumais, 1997) and similarity metrics derived from Wordnet (Miller & Fellbaum, 1991).

The spatial and temporal signatures of word production components

This paper presents the results of a comprehensive meta-analysis of the relevant imaging literature on word production (82 experiments). In addition to the spatial overlap of activated regions, we also analyzed the available data on the time course of activations. The analysis specified regions and time windows of activation for the core processes of word production: lexical selection, phonological code retrieval, syllabification, and phonetic/articulatory preparation. A comparison of the word production results with studies on auditory word/non-word perception and reading showed that the time course of activations in word production is, on the whole, compatible with the temporal constraints that perception processes impose on the production processes they affect in picture/word interference paradigms.

Dorsal and ventral streams: a framework for understanding aspects of the functional anatomy of language

Despite intensive work on language-brain relations, and a fairly impressive accumulation of knowledge over the last several decades, there has been little progress in developing large-scale models of the functional anatomy of language that integrate neuropsychological, neuroimaging, and psycholinguistic data. Drawing on relatively recent developments in the cortical organization of vision, and on data from a variety of sources, we propose a new framework for understanding aspects of the functional anatomy of language which moves towards remedying this situation. The framework posits that early cortical stages of speech perception involve auditory fields in the superior temporal gyrus bilaterally (although asymmetrically). This cortical processing system then diverges into two broad processing streams, a ventral stream, which is involved in mapping sound onto meaning, and a dorsal stream, which is involved in mapping sound onto articulatory-based representations. The ventral stream projects ventro-laterally toward inferior posterior temporal cortex (posterior middle temporal gyrus) which serves as an interface between sound-based representations of speech in the superior temporal gyrus (again bilaterally) and widely distributed conceptual representations. The dorsal stream projects dorso-posteriorly involving a region in the posterior Sylvian fissure at the parietal-temporal boundary (area Spt), and ultimately projecting to frontal regions. This network provides a mechanism for the development and maintenance of "parity" between auditory and motor representations of speech. Although the proposed dorsal stream represents a very tight connection between processes involved in speech perception and speech production, it does not appear to be a critical component of the speech perception process under normal (ecologically natural) listening conditions, that is, when speech input is mapped onto a conceptual representation. We also propose some degree of bi-directionality in both the dorsal and ventral pathways. We discuss some recent empirical tests of this framework that utilize a range of methods. We also show how damage to different components of this framework can account for the major symptom clusters of the fluent aphasias, and discuss some recent evidence concerning how sentence-level processing might be integrated into the framework.

Cherry pit primes Brad Pitt: Homophone priming effects on young and older adults' production of proper names

This study investigated why proper names are difficult to retrieve, especially for older adults. On intermixed trials, young and older adults produced a word for a definition or a proper name for a picture of a famous person. Prior production of a homophone (e.g., pit) as the response on a definition trial increased correct naming and reduced tip-of-the-tongue experiences for a proper name (e.g., Pitt) on a picture-naming trial. Among participants with no awareness of the homophone manipulation, older but not young adults showed these homophone priming effects. With a procedure that reduced awareness effects (Experiment 2), prior production of a homophone improved correct naming only for older adults, but speeded naming latency for both age groups. We suggest that representations of proper names are susceptible to weak connections that cause deficits in the transmission of excitation, impairing retrieval especially in older adults. We conclude that homophone production strengthens phonological connections, increasing the transmission of excitation.

I'm sitting here feeling aphasic! A study of recurrent perseverative errors elicited in unimpaired speakers

In this study, the recurrent perseverative errors produced by 44 speakers without impairment were examined in picture naming and reading aloud tasks under a fast response deadline. The proportion of perseverative relative to non-perseverative errors was greater in picture naming, the more error-prone task, than in reading aloud. Additionally, although perseverative errors were less likely to be related to the target than non-perseverative errors, the overall distribution of perseverative and non-perseverative errors in each task was similar. It is concluded that the perseverative errors produced by the participants reflected both the degree and level at which language processing efficiency was reduced in each task. This is consistent with a more recent account of perseveration as a result of normally existing persistent activation overcoming weakened activation of a target at any level of language processing. These results are compared with recent studies of recurrent perseverative errors produced by people with aphasia in light of the cognitive neuropsychological assumption that speakers with and without impairment utilise a common language processing system.

Testing predictions of the interactive activation model in recovery from aphasia after treatment

This paper presents preliminary results of pre- and post-treatment error analysis from an aphasic patient with anomia. The Interactive Activation (IA) model of word production (Dell, Schwartz, Martin, Saffran, & Gagnon, 1997) is utilized to make predictions about the anticipated changes on a picture naming task and to explain emerging patterns. Error patterns are viewed in light of two putative mechanisms within the IA network, connection strength, and rate of decay. The results suggest that while these mechanisms can successfully account for the magnitude and order of specific errors (e.g., predominance of semantic paraphasias and nonwords followed by formal paraphasias under the conditions of weak connections), the treatment may have influenced the occurrence/absence of some error types.

Management of anomia

Anomia is a complex, commonly occurring symptom of aphasia with different underlying causes. A number of behavioral approaches to rehabilitation of anomia have been described. Some are restitutive in nature and attempt to reactivate lexical-semantic or phonological representations to improve word retrieval. Others are intended to reorganize language functions by engaging alternative cognitive systems to mediate word retrieval or by exploiting residual abilities to circumvent the impairment. A better appreciation of the characteristics of an individual's naming deficit may assist the clinician in selecting appropriate interventions for restitution or substitution of function in the management of this disorder.

Language processing: functional organization and neuroanatomical basis

Earlier formulations of the relation of language and the brain provided oversimplified accounts of the nature of language disorders, classifying patients into syndromes characterized by the disruption of sensory or motor word representations or by the disruption of syntax or semantics. More recent neuropsychological findings, drawn mainly from case studies, provide evidence regarding the various levels of representations and processes involved in single-word and sentence processing. Lesion data and neuroimaging findings are converging to some extent in providing localization of these components of language processing, particularly at the single-word level. Much work remains to be done in developing precise theoretical accounts of sentence processing that can accommodate the observed patterns of breakdown. Such theoretical developments may provide a means of accommodating the seemingly contradictory findings regarding the neural organization of sentence processing.

Psycholinguistic norms for action photographs in French and their relationships with spoken and written latencies

A set of 142 photographs of actions (taken from Fiez & Tranel, 1997) was standardized in French on name agreement, image agreement, conceptual familiarity, visual complexity, imageability, age of acquisition, and duration of the depicted actions. Objective word frequency measures were provided for the infinitive modal forms of the verbs and for the cumulative frequency of the verbal forms associated with the photographs. Statistics on the variables collected for action items were provided and compared with the statistics on the same variables collected for object items. The relationships between these variables were analyzed, and certain comparisons between the current database and other similar published databases of pictures of actions are reported. Spoken and written naming latencies were also collected for the photographs of actions, and multiple regression analyses revealed that name agreement, image agreement, and age of acquisition are the major determinants of action naming speed. Finally, certain analyses were performed to compare object and action naming times. The norms and the spoken and written naming latencies corresponding to the pictures are available on the Internet (http://www.psy.univ-bpclermont.fr/~pbonin/pbonin-eng.html) and should be of great use to researchers interested in the processing of actions.

A method for studying the evolution of naming error types in the recovery of acute aphasia: a single-patient and single-stimulus approach

In this study, we present a method for analysing the evolution of picture naming errors in the follow-up of single patients affected by acute aphasia. In particular, we have based our analysis on the presence of response type inconsistency, as patients often fail to give the same type of response to the same stimulus at a task repetition attempted after a short time. Due to the uncertain definition of the type of response associated to a given stimulus for each stage of the clinical course, the investigation of the factors underlying the transition between different types of response is a serious methodological challenge. The solution presented here is based on a multiple presentation of the same naming battery at different stages of the clinical course, on the estimation of the probability associated with each response type at each stage, and on the estimation of the transition probability between different response types from one clinical stage to another. The basic idea was to use the set of probabilities referred to above as single stimuli weights in the study of linear models; these permit to compare different types of responses and different types of transitions. We present the application of this method to the study of a single case, a woman affected by fluent aphasia examined twice in the first 2 weeks following stroke. Besides discussing empirical findings, we comment on the usefulness of this method for wider fields of inquiry.

Error Biases in Spoken Word Planning and Monitoring by Aphasic and Nonaphasic Speakers: Comment on Rapp and Goldrick (2000)

B. Rapp and M. Goldrick (2000) claimed that the lexical and mixed error biases in picture naming by aphasic and nonaphasic speakers argue against models that assume a feedforward-only relationship between lexical items and their sounds in spoken word production. The author contests this claim by showing that a feedforward-only model like WEAVER++ (W. J. M. Levelt, A. Roelofs, & A. S. Meyer, 1999b) exhibits the error biases in word planning and self-monitoring. Furthermore, it is argued that extant feedback accounts of the error biases and relevant chronometric effects are incompatible. WEAVER++ simulations with self-monitoring revealed that this model accounts for the chronometric data, the error biases, and the influence of the impairment locus in aphasic speakers.

The relationships between morphological and phonological errors in aphasic speech: data from a word repetition task

Current theories of single-word processing predict that in some cases brain damage should selectively impair morphological processes, resulting in the selective occurrence of morphological errors. However, such a selective pattern of errors has never been documented, and the available case studies report the systematic association of morphological and phonological (segmental) errors in the same subject. The number of relevant case reports is very small, however. To better understand the relationship between morphological and phonological processes, we analyzed the repetition performance of 26 subjects who produced morphological errors in a screening battery for aphasia. Although the results confirm that subjects who make morphological errors also invariably make phonological errors, the probabilities of the two types of errors are not (quantitatively) correlated. Furthermore, the relationship between morphological and phonological errors was asymmetrical: although all subjects who produced morphological errors also produced phonological errors, some aphasics who produced phonological errors did not also produce morphological errors. The one-way relationship between morphological and phonological errors could result either from the anatomical proximity of the structures involved in morphological and phonological processes, or from the functional inseparability of the two processes. The fact that phonological errors can occur either in isolation or in association with morphological errors could be attributed to the functional heterogeneity of phonological errors, and to the separability of the neural substrates involved in processing various aspects of phonological information.

What Is a TOT? Cognate and Translation Effects on Tip-of-the-Tongue States in Spanish-English and Tagalog-English Bilinguals

The authors induced tip-of-the-tongue states (TOTs) for English words in monolinguals and bilinguals using picture stimuli with cognate (e.g., vampire, which is vampiro in Spanish) and noncognate (e.g., funnel, which is embudo in Spanish) names. Bilinguals had more TOTs than did monolinguals unless the target pictures had translatable cognate names, and bilinguals had fewer TOTs for noncognates they were later able to translate. TOT rates for the same targets in monolinguals indicated that these effects could not be attributed to target difficulty. Two popular TOT accounts must be modified to explain cognate and translatability facilitation effects, and cross-language interference cannot explain bilinguals' increased TOTs rates. Instead the authors propose that, relative to monolinguals, bilinguals are less able to activate representations specific to each language.

Effects of frequency and similarity neighborhoods on pharmacists’ visual perception of drug names

To minimize drug name confusion errors, regulators, drug companies, and clinicians need tools that help them predict which names are most likely to be involved in confusions. Two experiments, carried out in the United States, examined the effects of stimulus frequency (i.e., how frequently a target name is prescribed), neighborhood frequency (i.e., how frequently prescribed are the "neighbors" of the target name), and neighborhood density (how many names are within a fixed distance of the target name) on the probability of pharmacists making an error in a visual perceptual identification task. In both experiments, the task was to correctly identify a series of blurry drug names after a 3s presentation on a computer monitor. In the first experiment, 45 pharmacists viewed 160 typewritten names, incorrectly identifying 60.6% of them. Random effects regression revealed a significant beneficial effect of stimulus frequency and a detrimental effect of neighborhood density. Significant two-way interactions were observed between stimulus frequency and neighborhood density and neighborhood frequency and neighborhood density. In the second experiment, 37 pharmacists viewed 156 handwritten drug names, incorrectly identifying 45.7%. Random effects regression revealed significant main effects of stimulus frequency and neighborhood density. These were contained within a significant three-way interaction: The interaction between stimulus frequency and neighborhood density was present at high but not low neighborhood frequency. Objectively measurable frequency and neighborhood characteristics have predictable effects on errors in pharmacists' visual perception. Organizations that coin and evaluate drug names, as well as hospitals, pharmacies, and health systems, should consider these characteristics when assessing visually confusing names.

The role of semantic complexity in treatment of naming deficits: training semantic categories in fluent aphasia by controlling exemplar typicality

The effect of typicality of category exemplars on naming was investigated using a single subject experimental design across participants and behaviors in 4 patients with fluent aphasia. Participants received a semantic feature treatment to improve naming of either typical or atypical items within semantic categories, while generalization was tested to untrained items of the category. The order of typicality and category trained was counterbalanced across participants. Results indicated that patients trained on naming of atypical exemplars demonstrated generalization to naming of intermediate and typical items. However, patients trained on typical items demonstrated no generalized naming effect to intermediate or atypical examples. Furthermore, analysis of errors indicated an evolution of errors throughout training, from those with no apparent relationship to the target to primarily semantic and phonemic paraphasias. Performance on standardized language tests also showed changes as a function of treatment. Theoretical and clinical implications regarding the impact of considering semantic complexity on rehabilitation of naming deficits in aphasia are discussed.

An investigation of semantic errors in unimpaired and Alzheimer's speakers of Italian

Semantic errors are a common type of slip of the tongue for normal speakers; they are also considered to be the hallmark of progressive diseases that affect semantic memory such as Alzheimer's Disease (AD) and semantic dementia. In unimpaired speakers, semantic errors have been shown to be affected by syntactic variables. For example, Marx (1999) has shown that speakers of a gendered language such as German tend to substitute a target with another word that shares the same grammatical gender with the target more often than chance would predict. This finding suggests that errors occur at a level at which lexical information about the target is activated and retrieved. Here, we assess whether such an effect of syntactic variables (gender) also holds in experimental tasks designed to induce errors in unimpaired speakers of Italian (another gendered language) and whether this effect can also be observed in the semantic errors produced in the same task by AD patients. We found that for the unimpaired speakers, the gender of the target word constrained the error committed, while this was not the case for the AD patients. We take this finding to suggest a different locus for the errors in the two populations: while the semantic errors by the unimpaired speakers occur because of mis-selection of a lexical entry due to lexical competition among semantically similar words, the errors by the AD patients occur because of insufficient activation of lexical representations.

The role of semantic complexity in treatment of naming deficits: training semantic categories in fluent aphasia by controlling exemplar typicality

The effect of typicality of category exemplars on naming was investigated using a single subject experimental design across participants and behaviors in 4 patients with fluent aphasia. Participants received a semantic feature treatment to improve naming of either typical or atypical items within semantic categories, while generalization was tested to untrained items of the category. The order of typicality and category trained was counterbalanced across participants. Results indicated that patients trained on naming of atypical exemplars demonstrated generalization to naming of intermediate and typical items. However, patients trained on typical items demonstrated no generalized naming effect to intermediate or atypical examples. Furthermore, analysis of errors indicated an evolution of errors throughout training, from those with no apparent relationship to the target to primarily semantic and phonemic paraphasias. Performance on standardized language tests also showed changes as a function of treatment. Theoretical and clinical implications regarding the impact of considering semantic complexity on rehabilitation of naming deficits in aphasia are discussed.

Phoneme frequency effects in jargon aphasia: a phonological investigation of nonword errors

This study investigates the nonwords produced by a jargon speaker, LT. Despite presenting with severe neologistic jargon, LT can produce discrete responses in picture naming tasks thus allowing the properties of his jargon to be investigated. This ability was exploited in two naming tasks. The first showed that LT's nonword errors are related to their targets despite being generally unrecognizable. This relatedness appears to be a general property of his errors suggesting that they are produced by lexical rather than nonlexical means. The second naming task used a set of stimuli controlled for their phonemic content. This allowed an investigation of target phonology at the level of individual phonemes. Nonword responses maintained the English distribution of consonants and showed a significant relationship to the target phonologies. A strong influence of phoneme frequency was identified. High frequency consonants showed a pattern of frequent but indiscriminate use. Low frequency consonants were realised less often but were largely restricted to target related contexts rarely appearing as error phonology. The findings are explained within a lexical activation network with the proposal that the resting levels of phoneme nodes are frequency sensitive. Predictions for the recovery of jargon aphasia and suggestions for future investigations are made.

Utterance format affects phonological priming in the picture-word task: implications for models of phonological encoding in speech production

Picture-word experiments investigating the production of multiword utterances with distractors that are phonologically related to words in noninitial position have yielded inconsistent results, ranging from facilitation to inhibition. A comparison of these studies is complicated by differences in detail. In parallel to the empirical inconsistencies, different theoretical accounts of phonological encoding in speech production have been provided. In the present article, the authors propose a unitary account, which can in principle account for facilitation, null effects, and inhibition. It assumes a graded activation pattern of the elements within the scope of phonological advance planning. The account is tested in an experiment varying utterance format while keeping all other aspects constant. The results are consistent with the proposed unitary account.

Adult brain plasticity elicited by anomia treatment

We describe a study where a specific treatment method for word-finding difficulty (so-called contextual priming technique, which combines massive repetition priming with semantic priming) was applied with three chronic left hemisphere-damaged aphasics. Both before and after treatment, which focused on naming of a series of pictures, naming-related brain activity was measured by magnetoencephalography (MEG). Due to its excellent temporal resolution and good spatial resolution, we were able to track treatment-induced changes in cortical activity. All three subjects showed improved naming of the trained items. In all subjects, a single source area, located in the left inferior parietal lobe, close to the lesioned area, displayed statistically significant training-induced changes. This effect was of long latency as it started 300-600 msec after picture presentation. The change in activation was specific to training, as it could not be accounted for by variation of cortical dynamics associated with increased proportion of correct answers. Our interpretation is that the training effect reflects more effective phonological encoding and storage of the trained items through the engagement of a left hemispheric word-learning system. This is in line with recent functional imaging studies, which have linked left inferior parietal lobe activity to the phonological storage component of the verbal working memory, as well as with theoretical arguments stating that the primary role of the phonological loop is to acquire new words. Finally, the MEG results showed no evidence of increased right hemisphere participation following training, supporting the view that restoration of language-related networks in the damaged left hemisphere is crucial for anomia recovery.

Grammatical class effects in brain-damaged patients: functional locus of noun and verb deficit

Two patients are described with grammatical class dissociation: CG, a semantic-dementia patient who presented a disproportionate impairment of nouns compared to verbs; SA, a patient with a left parietal lesion who presented impaired sentence production and a disproportionate deficit for verbs compared to nouns. The results are discussed within the current models on semantic memory and lexical access.

Information flow in the mental lexicon during speech planning: evidence from event-related brain potentials

A major issue in speech production research is the question of how speakers retrieve words from the so-called mental lexicon. Current models of lexical retrieval converge on the assumption that category associates of a target word are semantically activated during speech planning. However, the question of whether these competitors are also phonologically activated is less agreed on. Past research has addressed this issue by testing whether lexical retrieval of a picture name (e.g. sheep) affects, or is affected by, the processing of a word that is phonologically related to a semantic category associate to the picture name (e.g. goal, phonologically related to goat). Behavioral studies have failed to obtain such so-called mediated priming effects, but have been questioned on the grounds of possibly insufficient task sensitivity. As such priming effects have reliably been obtained with event-related brain potentials in word recognition, we used this approach for testing these effects in lexical retrieval during speech planning. Our results consistently demonstrate the absence of mediated priming effects, putting strong constraints on the activation flow in the mental lexicon during speech planning.

Mechanisms underlying perseveration in aphasia: evidence from a single case study

Aphasic individuals often inappropriately and unintentionally repeat recent responses, errors termed recurrent perseverations. In a series of picture naming experiments, we investigated the impact of manipulating stimulus factors on the number of perseverations produced by an aphasic patient (E.B.) with markedly impaired naming skills. E.B. produced significantly more perseverations to pictures with low frequency names and following stimulus repetition. In contrast, semantic relatedness and presentation rate failed to influence perseveration. Our results are considered in the context of theories that relate recurrent perseverations to intact priming mechanisms [Brain 121 (1998) 1641; Aphasiology 12 (1998) 319; J. Exp. Psychol. Learn. Mem. Cogn. 19 (1993) 243]. We conclude that these theories can correctly predict some but not all aspects of E.B.'s perseverations. In particular, they failed to predict that: (1) perseverations often appeared to reflect the earlier sequential proximity of stimuli and responses; and (2) perseverations became less likely as more experimental trials intervened, a trend that did not interact with presentation rate. We review evidence relating recurrent perseverations to neuromodulatory deficits and we conclude that a theory of the functional role of neuromodulation in the cerebral cortex proposed by Hasselmo [Neural Netw. 7 (1994) 13] is capable of accounting for all aspects of E.B.'s perseverative behavior.

Semantic priming in number naming

The issue of semantic and non-semantic conversion routes for numerals is still debated in numerical cognition. We report two number-naming experiments in which the target numerals were preceded by another numeral (prime). The primes and targets could be presented either in arabic (digit) notation or in verbal (alphabetical) notation. The results reveal a semantically related distance effect: Latencies are fastest when the prime has the same value as the target and increase when the distance between prime and target increases. We argue that the present results are congruent with the idea that the numerals make access to an ordered semantic number line common to all notations, as the results are the same for within-notation priming (arabic-arabic or verbal-verbal) and between-notations priming (arabic-verbal or verbal-arabic). The present results also point to a rapid involvement of semantics in the naming of numerals, also when the numerals are words. As such, they are in line with recent claims of rapid semantic mediation in word naming.

Aphasic naming in Spanish: predictors and errors

Sixteen Spanish aphasic patients named drawings of objects on three occasions. Multiple regression analyses were carried out on the naming accuracy scores. For the patient group as a whole, naming was affected by visual complexity, object familiarity, age of acquisition, and word frequency. The combination of variables predicted naming accuracy in 15 of the 16 individual patients. Age of acquisition, word frequency, and object familiarity predicted performance in the greatest number of patients, while visual complexity, imageability, animacy, and length all affected performance in at least two patients. High proportions of semantic and phonological errors to particular objects were associated with objects having early learned names while high proportions of no-response errors were associated with low familiarity and low visual complexity. It is suggested that visual complexity and object familiarity affect the ease of object recognition while word frequency affects name retrieval. Age of acquisition may affect both stages, accounting for its influence in patients with a range of different patterns of disorder.

Patterns of phonological errors as a function of a phonological versus an articulatory locus of impairment

We present the case of two aphasic patients: one with fluent speech, MM, and one with dysfluent speech, DB. Both patients make similar proportions of phonological errors in speech production and the errors have similar characteristics. A closer analysis, however, shows a number of differences. DB's phonological errors involve, for the most part, simplifications of syllabic structure; they affect consonants more than vowels; and, among vowels, they show effects of sonority/complexity. This error pattern may reflect articulatory difficulties. MM's errors, instead, show little effect of syllable structure, affect vowels at least as much as consonants and, and affect all different vowels to a similar extent. This pattern is consistent with a more central impairment involving the selection of the right phoneme among competing alternatives. We propose that, at this level, vowel selection may be more difficult than consonant selection because vowels belong to a smaller set of repeatedly activated units.

Phonological neighborhood effects in aphasic speech errors: spontaneous and structured contexts

The current study investigates the influence of phonological neighborhoods on the accuracy of speech production in aphasia by examining errors produced in both spontaneous and structured speech tasks. Characteristics of the phonological neighborhoods of spontaneously produced aphasic errors are compared to the neighborhood characteristics of correctly produced targets in a picture description task. Accuracy of picture naming is also examined with reference to the phonological neighborhood characteristics of the stimuli. Results show that frequency of occurrence and neighborhood density play a facilitative role in speech production, replicating findings from recent studies with normal subjects. It is argued that the results are most parsimoniously explained within an interactive activation framework of lexical access.

The interplay of meaning, sound, and syntax in sentence production

A discussion of modularity in language production processes, with special emphasis on processes for retrieving words and building syntactic structures for a to-be-uttered sentence, is presented. The authors' 1st goal was to assess the extent to which information processing is encapsulated between different processing stages. In particular, they assessed whether the input from one processing stage to the next is minimal and whether the flow of information in the system is strictly unidirectional. On the basis of the reviewed evidence, they conclude that both assumptions have to be revised. Their 2nd goal was to propose an altemative framework that does not assume strict encapsulation but that maintains multiple levels of integration for production.

Recency effects for meaning and form in word selection

Three experiments examined the contribution of phonological availability in selecting words as predicted by interactive activation models of word production. Homophonous words such as week and weak permitted a word's phonological form to be activated on priming trials without selection of its meaning or lemma. Recent production of a homophone failed to significantly increase production of its twin as a sentence completion. However, speakers were significantly more likely to complete a sentence with a recently read or generated unambiguous word. This increase in response probability was unaffected by word frequency. The results constrain the degree to which experience and phonological availability may affect word selection in spoken language production.

Reassessing working memory: comment on Just and Carpenter (1992) and Waters and Caplan (1996)

M. A. Just and P. A. Carpenter's (1992) capacity theory of comprehension posits a linguistic working memory functionally separated from the representation of linguistic knowledge. G. S. Waters and D. Caplan's (1996) critique of this approach retained the notion of a separate working memory. In this article, the authors present an alternative account motivated by a connectionist approach to language comprehension. In their view, processing capacity emerges from network architecture and experience and is not a primitive that can vary independently. Individual differences in comprehension do not stem from variations in a separate working memory capacity; instead they emerge from an interaction of biological factors and language experience. This alternative is argued to provide a superior account of comprehension results previously attributed to a separate working memory capacity.

Phonology: a review and proposals from a connectionist perspective

A parallel distributed processing (PDP) model of phonological processing is developed, including components to support repetition, auditory processing, comprehension, and language production. From the performance of the PDP reading model of Plaut, McClelland, Seidenberg, and Patterson (1996), it is inferred that the acoustic-articulatory motor pattern associator that supports repetition provides the basis for phonological sequence knowledge. From the observation that many patients make phonemic paraphasic errors in language production, as in repetition, it is argued that there must be a direct link between distributed concept representations (lexical semantic knowledge) and this network representation of sequence knowledge. In this way, both lexical semantic and phonotactic constraints are brought to bear on language production. The literature on phonological function in normal subjects (slip-of-the-tongue corpora) and in patients with aphasia is critically reviewed from this perspective. The relationship between acoustic and articulatory motor representations in the process of phonetic perception is considered. Repetition and reproduction conduction aphasia are reviewed in detail and extended consideration is given to the representation of auditory verbal short-term memory in the model. Finally, the PDP model is reconciled with information processing models of phonological processing, including that of Lichtheim, and with current knowledge of the anatomic localization of phonological processing. Although no simulations of the model were run, a number of simulation studies are proposed.

Differential effects of unilateral lesions on language production in children and adults

We present the first direct comparison of language production in brain-injured children and adults, using age-corrected z scores for multiple lexical and grammatical measures. Spontaneous speech samples were elicited in a structured biographical interview from 38 children (5-8 years of age), 24 with congenital left-hemisphere damage (LHD) and 14 with congenital right-hemisphere damage (RHD), compared with 38 age- and gender-matched controls, 21 adults with unilateral injuries (14 LHD and 7 RHD), and 12 adult controls. Adults with LHD showed severe and contrasting profiles of impairment across all measures (including classic differences between fluent and nonfluent aphasia). Adults with RHD (and three nonaphasic adults with LHD) showed fluent but disinhibited and sometimes empty speech. None of these qualitative or quantitative deviations were observed in children with unilateral brain injury, who were in the normal range for their age on all measures. There were no significant differences between children with LHD and RHD on any measure. When LHD children were compared directly with LHD adults using age-corrected z scores, the children scored far better than their adult counterparts on structural measures. These results provide the first systematic confirmation of differential free-speech outcomes in children and adults and offer strong evidence for neural and behavioral plasticity following early brain damage.

Gewißt wu - gewußt wie! Was die Versprecherforschung über Sprachproduktion weiß

Zusammenfassung. Die Art und Weise, wie wir uns versprechen, gibt Aufschluß über Prozesse der Sprachproduktion. Der erste Teil des Beitrags gibt eine Einführung in den Themenbereich und skizziert historische Ansätze linguistischer sowie psychologischer Versprecherforschung. In Teil zwei werden verschiedene Versprecherarten und Annahmen vorgestellt, die sich bezüglich einzelner Prozeßphasen aus ihnen ableiten lassen. Diese werden im Zusammenhang mit aktuellen chronometrischen Daten der experimentellen Sprachproduktionsforschung diskutiert. Es geht dabei immer um eine Frage, nämlich um die zeitliche Koordination einzelner Prozeßstufen und um ihre Möglichkeit, untereinander zu interagieren.

Language deficits, localization, and grammar: evidence for a distributive model of language breakdown in aphasic patients and neurologically intact individuals

Selective deficits in aphasic patients' grammatical production and comprehension are often cited as evidence that syntactic processing is modular and localizable in discrete areas of the brain (e.g., Y. Grodzinsky, 2000). The authors review a large body of experimental evidence suggesting that morpho-syntactic deficits can be observed in a number of aphasic and neurologically intact populations. They present new data showing that receptive agrammatism is found not only over a range of aphasic groups, but is also observed in neurologically intact individuals processing under stressful conditions. The authors suggest that these data are most compatible with a domain-general account of language, one that emphasizes the interaction of linguistic distributions with the properties of an associative processor working under normal or suboptimal conditions.

The influence of phonological context on the sound errors of a speaker with Wernicke's aphasia

A corpus of phonological errors produced in narrative speech by a Wernicke's aphasic speaker (R.W.B.) was tested for context effects using two new methods for establishing chance baselines. A reliable anticipatory effect was found using the second method, which estimated chance from the distance between phoneme repeats in the speech sample containing the errors. Relative to this baseline, error-source distances were shorter than expected for anticipations, but not perseverations. R.W.B.'s anticipation/perseveration ratio measured intermediate between a nonaphasic error corpus and that of a more severe aphasic speaker (both reported in Schwartz et al., 1994), supporting the view that the anticipatory bias correlates to severity. Finally, R.W.B's anticipations favored word-initial segments, although errors and sources did not consistently share word or syllable position.

Assessing working memory and language comprehension in Alzheimer's disease

Studies of language impairments in patients with Alzheimer's disease have often assumed that impairments in linguistic working memory underlie comprehension deficits. Assessment of this hypothesis has been hindered both by vagueness of key terms such as "working memory" and by limitations of available working memory tasks, in that many such tasks either seem to have little relationship to language comprehension or are too confusing or difficult for Alzheimer's patients. Four experiments investigated the usefulness of digit ordering, a new task assessing linguistic working memory and/or language processing skill, in normal adults and patients with probable Alzheimer's disease. The digit ordering task was shown to be strongly correlated with the degree of dementia in Alzheimer's patients. The task correlated with measures of language processing on which patients and normal controls performed differently. The results are interpreted as indicating that linguistic representations, linguistic processing, and linguistic working memory are intertwined, such that a deficit of one (e.g., working memory) cannot be said to "cause" a deficit in the other. The implications of this approach are explored in terms of task demands in comprehension and memory measures, and interpretation of previous results in the literature.

Short-term retention of lexical-semantic representations: Implications for speech production

Patients with semantic STM deficits have difficulty comprehending sentences that require the retention of several lexical-semantic representations prior to their integration into higher-level propositions (Martin, 1995; Martin & Romani, 1994). In Experiment 1, patients with a semantic retention deficit had difficulty with the same type of constructions in speech production, namely noun phrases with one or two prenominal adjectives. Their performance improved when they could produce the nouns and adjectives in sentence form, which placed smaller demands on lexical-semantic retention. In Experiment 2 these patients were better able to produce syntactically complex sentences than the prenominal adjective phrases having an equal number of content words, indicating that the findings in Experiment 1 could not be attributed to syntactic complexity. These patients produced more pauses in the sentence constructions in Experiments 1 and 2, suggesting that the timing of such productions is abnormal. In contrast, patient EA, with a phonological retention deficit, performed better than the patients with a semantic retention deficit on the AN phrases despite having a smaller STM span. She showed no significant benefit of producing sentence compared to phrase constructions, and also made fewer and shorter pauses than the other patients. These findings support the multiple capacities view of verbal working memory and suggest that the same semantic retention capacity used in language comprehension is used in speech production.

Psycholinguistic models of speech development and their application to clinical practice

This article presents an introduction to psycholinguistic models of speech development. Two specific types of models are addressed: box-and-arrow models and connectionist or neural network models. We review some historical and some current models and discuss recent applications of such models to the management of speech impairment in children. We suggest that there are two ways in which a psycholinguistic approach can influence clinical practice: by directly supplementing a speech-language pathologist's repertoire of assessment and treatment approaches and by offering a new way to conceptualize speech impairment in children.

Does agrammatic speech constitute a regression to child language? A three-way comparison between agrammatic, child, and normal ellipsis

When children are in the process of learning their mother tongue, they show frequent use of nonfinite clauses, even though they produce finite clauses at the same time, thereby demonstrating the availability of the functional domain associated with finiteness. In this study the hypothesis was tested that this behavior results from an overuse of the normal elliptical repertoire that has also been observed in agrammatic aphasia. The purpose of this overuse is prevention of computational overload. In support of the hypothesis it was found that children behaved very similar to aphasics and normal adults with respect to the following parameters: (a) distribution of types of ellipsis, (b) elaboration of ellipses, (c) word order, (d) subject omission, (e) frequency of weak subject pronouns, and (f) verb type (eventivity). The results also support the Jackson/Jakobson regression hypothesis, at least at the grammatical level.

Processing of grammatical gender in normal and aphasic speakers of Russian

Sensitivity to grammatical gender was investigated in 22 Russian-speaking aphasic patients, compared with young controls. Experiment 1 used a cued shadowing paradigm to assess gender priming (facilitation and/or inhibition of lexical access by a prenominal modifier with congruent, incongruent or neutral gender). Experiment 2 used a grammaticality judgment paradigm with similar stimuli. Normals showed significant interactions between gender and priming in Experiment 1 (facilitation for feminine and neuter nouns but not for masculines) and Experiment 2 (larger effects of context on feminine and neuter nouns) that we interpret as a Markedness Effect. Patients showed significant priming in Experiment 1 and above-chance accuracy in Experiment 2, but failed to show reduced effects for the least-marked masculine gender (the Markedness Effect) in either experiment. Context effects were not related to specific aphasic symptoms or subtypes in either experiment. However, canonical correlation revealed differential effects of specific aphasic symptoms on judgment accuracy (false alarms vs. misses). We conclude that knowledge of grammatical gender is spared in Russian aphasics, but gender processing is deviant. A possible model to account for these differences is discussed.

A neural correlate of syntactic encoding during speech production

Spoken language is one of the most compact and structured ways to convey information. The linguistic ability to structure individual words into larger sentence units permits speakers to express a nearly unlimited range of meanings. This ability is rooted in speakers' knowledge of syntax and in the corresponding process of syntactic encoding. Syntactic encoding is highly automatized, operates largely outside of conscious awareness, and overlaps closely in time with several other processes of language production. With the use of positron emission tomography we investigated the cortical activations during spoken language production that are related to the syntactic encoding process. In the paradigm of restrictive scene description, utterances varying in complexity of syntactic encoding were elicited. Results provided evidence that the left Rolandic operculum, caudally adjacent to Broca's area, is involved in both sentence-level and local (phrase-level) syntactic encoding during speaking.

Self-organizing dynamics of lexical access in normals and aphasics

The goal of this article is to illustrate the application of self-organizing dynamics in the design of a model of lexical access. We focus particularly on the mapping of sound structure on to the lexicon and the influence of that structure on lexical access. The approach is tested in a series of two sets of simulations that explicate how lexical access might occur in normal subjects and aphasic patients. Both sets of simulations address the behavioral effects of both phonological and phonetic variability of prime stimuli on the magnitude of semantic priming. Results show that the model can successfully account for the behavioral effects associated with several kinds of acoustic manipulation, competitor presence, and the unfolding of those effects over time--primarily because it balances three important control parameters: resting lexical activation, positive feedback, and negative feedback. These simulations are offered as support (in the form of an existence proof) that deficits in the degree of lexical activation can account for the lexical processing impairments shown by Broca's aphasics who have reduced lexical activation, and Wernicke's aphasics who have increased lexical activation. Overall, results suggest that the present approach promises to offer a coherent theoretical framework within which to link empirical evidence in language processing and cognitive neuroscience in terms of possible underlying mechanisms.

Connectionist psycholinguistics: capturing the empirical data

Connectionist psycholinguistics is an emerging approach to modeling empirical data on human language processing using connectionist computational architectures. For almost 20 years, connectionist models have increasingly been used to model empirical data across many areas of language processing. We critically review four key areas: speech processing, sentence processing, language production, and reading aloud, and evaluate progress against three criteria: data contact, task veridicality, and input representativeness. Recent connectionist modeling efforts have made considerable headway toward meeting these criteria, although it is by no means clear whether connectionist (or symbolic) psycholinguistics will eventually provide an integrated model of full-scale human language processing.

When ottoman is easier than chair: an inverse frequency effect in jargon aphasia

This paper presents evidence of an inverse frequency effect in jargon aphasia. The subject (JP) showed a pre-disposition for low frequency word production on a range of tasks, including picture naming, sentence completion and naming in categories. Her real word errors were also striking, in that these tended to be lower in frequency than the target. Reading data suggested that the inverse frequency effect was present only when production was semantically mediated. It was therefore hypothesised that the effect was at least partly due to the semantic characteristics of low frequency items. Some support for this was obtained from a comprehension task showing that JP's understanding of low frequency terms, which she often produced as errors, was superior to her understanding of high frequency terms. Possible explanations for these findings are considered.