Grammatical category-specific deficits in bilingual aphasia

We report the naming performance of an early and highly proficient Spanish-Catalan bilingual (JPG) suffering from Primary Progressive Aphasia (PPA). JPG's performance revealed a grammatical category-specific deficit, with worse performance in naming verbs than nouns. This dissociation was present in oral and written naming and in his two languages, and it seems to stem from damage to, at least, the lexical level. Despite the fact that JPG's performance was qualitatively very similar across languages, his second language seemed to be more affected than his first language. These results indicate that the cortical organization of the two languages of highly proficient bilinguals follow similar organizational principles, one of this principles being grammatical class.     

Reconstructive retrieval deficits in Broca's aphasia

Anterior aphasic patients' ability to utilize the phonemic and/or semantic features of verbal material for retention purposes was investigated. In the first experiment, patients were asked to either detect word repetitions, phoneme repetitions, or rhymes in a list of items. The aphasics performed well on word and phoneme repetition detection but below both normals and amnesic Korsakoffs on rhyme detection. In the second experiment the patients were instructed to analyze either the physical, phonemic, or semantic features of words they were later asked to recognize. Aphasics were differentially affected (as were normals) by these instructions: semantic feature analysis resulted in the best performance, followed by phonemic feature analysis. It was concluded that anterior aphasics can analyze, recirculate, and even store the phonemic features of words, but find difficulty in reconstructing the originally presented item from these features.     

Recognition deficits resulting from focussed attention in aphasia

Summary Two nonverbal short-term memory tasks, a Picture Recognition and a Paired Association Task, were performed by matched groups of aphasics and brain-damaged controls (N=52 each). For both tasks the alternatives on the answer forms differed systematically on three dimensions, one of which had been highlighted experimentally for each item before the target picture was indicated. In both tasks aphasics made more errors than braindamaged controls only with respect to those features that had been stressed beforehand; they were less able than controls to take advantage of focussed attention. The number of these errors was correlated with performance in the Token Test, a picture naming and a word comprehension task.There were no differences between the groups in response to variations in the semantic saliency of the discriminating features or in the semantic and phonetic relationship between words denoting the reference stimuli. The lack of interactions might have been due to a strong ceiling effect in both tasks.     

Discourse in aphasia: Integration deficits in processing reference

The present study investigated moderately impaired aphasic subjects' ability to integrate information across sentences by having them identify antecedents for ambiguous pronouns in brief narratives. In order to disambiguate the pronouns, the subjects had to consult either textual cues and/or extratextual cues. In addition, the subjects' ability to retrieve factual information was measured by having them identify explicitly stated noun referents. The results show that the aphasic subjects had significant difficulty using textual cues to resolve referents when the referents were not readily accessible through world knowledge. The patients had little difficulty interpreting referents which were recoverable from world knowledge or were stated explicitly. The explanatory power of world knowledge effects, grammatical class effects, memory effects, and linguistic integration effects in accounting for the deficit pattern observed is considered.     

Production deficits in aphasia: A voice-onset time analysis

An experimental study was conducted to examine phonetic and phonemic deficits in the speech production of aphasics. Subjects included four Broca's aphasics, four Conduction aphasics, five Wernicke's aphasics, one nonaphasic dysarthric patient, and four normal controls. The subjects read a list of words containing word-initial stop consonants which were subsequently measured acoustically for voice-onset time. The results showed that Broca's aphasics exhibit a more severe production disorder than Conduction aphasics who in turn exhibit a more severe disorder than Wernicke's aphasics, in accord with clinical observations. In addition, although Broca's aphasics produced both phonetic and phonemic errors, the results showed that they have a pervasive phonetic disorder which affects their correct target productions as well as the total number of phonetic errors produced. This deficit however seems to be a speech deficit rather than a low-level motor control problem. In contrast, the Wernicke's aphasics show a deficit characterized by isolated phonemic mistargeting errors. Finally, the pattern of productions for the Conduction aphasics indicates that some patients show a predominantly phonetic disorder similar to the Broca's aphasics and others show predominantly a phonemic disorder similar to the Wernicke's aphasics.     

Processing passive sentences in aphasia: deficits and strategies

Broca's and Wernicke's aphasics' ability to process passive sentences in the absence of semantic cues was investigated in an experiment which varies syntactic complexity and word order. The results indicate that Broca and Wernicke patients use different strategies for sentence comprehension. Wernicke patients use rather general strategies for interpretation, which assign syntactic function according to sequential arrangements of words. Broca's aphasics, by contrast, base their interpretation on specific structural elements of the sentence's surface form, without, however, being able to exploit the full syntactic information of these elements. The different strategies are interpreted to reflect differential underlying deficits.     

The neural basis of syntactic deficits in primary progressive aphasia

Patients with primary progressive aphasia (PPA) vary considerably in terms of which brain regions are impacted, as well as in the extent to which syntactic processing is impaired. Here we review the literature on the neural basis of syntactic deficits in PPA. Structural and functional imaging studies have most consistently associated syntactic deficits with damage to left inferior frontal cortex. Posterior perisylvian regions have been implicated in some studies. Damage to the superior longitudinal fasciculus, including its arcuate component, has been linked with syntactic deficits, even after gray matter atrophy is taken into account. These findings suggest that syntactic processing depends on left frontal and posterior perisylvian regions, as well as intact connectivity between them. In contrast, anterior temporal regions, and the ventral tracts that link frontal and temporal language regions, appear to be less important for syntax, since they are damaged in many PPA patients with spared syntactic processing.     

Constraint on word-learning constraints

Many researchers have agreed that word learning in young children is guided by so-called "word-learning principles." However, these principles may make it difficult to learn a substantial part of the lexicon unless they are appropriately controlled. To learn proper names, the taxonomic assumption and/or the shape bias must be overridden; to learn names for substances, withdrawal of the whole-object assumption and/or the shape bias is required; and to learn lexical hierarchies, the mutual exclusivity assumption must be suspended. In certain languages, syntax can provide useful information in this situation. For example, if a novel noun is given to an object for which the name is known in the syntactic frame "This is X," English-speaking children may assume the noun to be a proper noun, and this will help them override the taxonomic assumption. However, this information is not available to Japanese children, since the Japanese language does not have grammatical markers to flag the distinction between count nouns and mass nouns, or the distinction between proper nouns and common nouns. In this paper, I discuss how Japanese children get around this problem.     

The development of a word-learning strategy

Two studies investigated young infants' use of the word-learning principle Mutual Exclusivity. In Experiment 1, a linear relationship between age and performance was discovered. Seventeen-month-old infants successfully used Mutual Exclusivity to map novel labels to novel objects in a preferential looking paradigm. That is, when presented a familiar and a novel object (e.g. car and phototube) and asked to "look at the dax", 17-month-olds increased looking to the novel object (i.e. phototube) above baseline preference. On these trials, 16-month-olds were at chance. And, 14-month-olds systematically increased looking to the familiar object (i.e. car) in response to hearing the novel label "dax". Experiment 2 established that this increase in looking to the car was due solely to hearing the novel label "dax". Several possible interpretations of the surprising form of failure at 14 months are discussed.     

Effects of morphological complexity on phonological output deficits in fluent and nonfluent aphasia

This study examined the effects of morphological complexity on aphasic speakers with lexical-phonological output deficits. Subjects were two fluent and two nonfluent aphasic speakers who repeated morphologically simple words at the same level of accuracy and whose errors were virtually all phonological in nature. They were asked to repeat a variety of morphologically complex (i.e., affixed) words. Results were interpreted within our two-stage model of lexical-phonological production (Kohn & Smith, 1994, 1995), which we expand to include a distinction between derivational and inflectional morphology. When comparing overall performance levels between morphologically simple and complex words, only three subjects exhibited more difficulty repeating the morphologically complex targets. Nevertheless, when comparing repetition accuracy between different types of morphologically complex words (e.g., derived vs. inflected), all four subjects displayed similar patterns. These findings suggested that while morphological complexity has different effects on the two stages within the lexical-phonological output system, the relative effects of different morphological structures are constant. At the level of error analysis, patterns of affix errors distinguished the nonfluent from the fluent subjects in ways that are reminiscent of the affix errors associated with agrammatic and paragrammatic speech. This finding raised questions concerning the relationship between morphosyntactic and morphophonological deficits.     

Selective delayed alternation deficits in dominantly inherited olivopontocerebellar atrophy

In order to characterize more completely the nature of the frontal lobe-type cognitive changes in patients with dominantly inherited olivopontocerebellar atrophy (OPCA) we administered two tasks sensitive to frontal system dysfunction, delayed alternation (DA) and delayed response (DR), to 12 patients from one OPCA family. Affected members from this family have previously been shown to have a marked and widespread cerebral (including frontal) cortical cholinergic reduction as severe as that observed in Alzheimer's disease. Performance on DA, but not on DR, was significantly impaired in the OPCA patients compared to that in the controls. We suggest that the DA deficits in OPCA could be a consequence of a loss of cholinergic innervation to orbitofrontal or possibly temporal cortical areas and/or damage to the integrity of the cerebello-frontal neuronal connections.     

Linguistic and neuropsychological deficits in crossed conduction aphasia. Report of three cases

This study describes the linguistic and neuropsychological findings in three right-handed patients with crossed conduction aphasia. Despite the location of the lesion in the right hemisphere, all patients displayed a combination of linguistic deficits typically found in conduction aphasia following analogous damage to the left hemisphere. Associated cognitive deficits varied across the three patients. In addition, all cases showed deficits classically attributed to non-dominant hemisphere damage (visuoperceptual deficits and reduced figural memory). As a result, lesion-behaviour relationships in our study sample indicate both dominant and non-dominant qualities of the right hemisphere.     

Selective deficit of conceptual structures in aphasia: Class versus thematic relations

Conceptual structures in aphasia were investigated by means of a nonverbal test. The understanding of class and thematic relationships was demonstrated to be selectively impaired according to varieties of aphasic deficit. Broca's aphasics showed difficulty evaluating a thematic relationship and did not differ from normal controls as far as class relationships were concerned. The opposite happened for Wernicke's aphasics whose defect seems to be selectively restricted to class relationships.     

Selective crossed aphasia in a trilingual aphasic patient followed by reciprocal antagonism

After surgical removal of a parasitic cyst in the right prerolandic area, an educated 25-year-old male exhibited obvious deficits in one of his three languages (Gujarati), with no measurable deficits in the other two (French and Malagasy). The patient spoke all three languages fluently before the operation. Gujarati and Malagasy had been acquired in infancy. Gujarati was the language of his parents and relatives. Malagasy the language of the local population. All the patient's schooling had been in French, the only language in which he was literate. He used French daily at work. Since the acquisition history for Gujarati and Malagasy was identical, while French had been acquired in a different context, one would have predicted, on the basis of W. Lambert and S. Fillenbaum's (1959, Canadian Journal of Psychology, 13, 28-34) hypothesis, that Gujarati and Malagasy should have been equally affected, with French possibly differently so. However, 8 months postoperatively, the patient had regained control of Gujarati, while Malagasy had deteriorated considerably, and his French remained unimpaired. Two years later, the patient had recovered full use of his three languages.     

Theories of spoken word recognition deficits in aphasia: evidence from eye-tracking and computational modeling

We used eye-tracking to investigate lexical processing in aphasic participants by examining the fixation time course for rhyme (e.g., carrot-parrot) and cohort (e.g., beaker-beetle) competitors. Broca’s aphasic participants exhibited larger rhyme competition effects than age-matched controls. A re-analysis of previously reported data (Yee, Blumstein, & Sedivy, 2008) confirmed that Wernicke’s aphasic participants exhibited larger cohort competition effects. Individual-level analyses revealed a negative correlation between rhyme and cohort competition effect size across both groups of aphasic participants. Computational model simulations were performed to examine which of several accounts of lexical processing deficits in aphasia might account for the observed effects. Simulation results revealed that slower deactivation of lexical competitors could account for increased cohort competition in Wernicke’s aphasic participants; auditory perceptual impairment could account for increased rhyme competition in Broca’s aphasic participants; and a perturbation of a parameter controlling selection among competing alternatives could account for both patterns, as well as the correlation between the effects. In light of these simulation results, we discuss theoretical accounts that have the potential to explain the dynamics of spoken word recognition in aphasia and the possible roles of anterior and posterior brain regions in lexical processing and cognitive control.     

Selective attention and executive functions deficits among criminal psychopaths

The present study examined whether psychopaths exhibit deficits in selective attention and executive functions. Prison inmates were assigned to either a “psychopath” group or a “control” group according to their scores on the PCL‐R [Hare, 1991: Toronto, Multi‐Health Systems]. The two groups were compared in terms of performance on the following tests: (1) D‐II cancellation, (2) Porteus Maze, (3) Modified Wisconsin Card Sorting, (4) Stroop Color Word Interference, (5) Trail Making, and (6) Tower of London. The results support the hypothesis of selective attention and specific executive function deficits among psychopaths. Specifically, psychopaths' abilities to maintain a plan and to inhibit irrelevant information were inferior to those of control participants. Aggr. Behav. 29:393–405, 2003. © 2003 Wiley‐Liss, Inc.     

Emergent constraints on word-learning: a computational perspective

In learning the meanings of words, children are guided by a set of constraints that give privilege to some potential meanings over others. These word-learning constraints are sometimes viewed as part of a specifically linguistic endowment. However, several recent computational models suggest concretely how word-learning - constraints included - might emerge from more general aspects of cognition, such as associative learning, attention and rational inference. This article reviews these models, highlighting the link between general cognitive forces and the word-learning they subserve. Ultimately, these cognitive forces might leave their mark not just on language learning, but also on language itself: in constraining the space of possible meanings, they place limits on cross-linguistic semantic variation.     

The relationship between phonological and morphological deficits in Broca's aphasia: further evidence from errors in verb inflection

A previous study of 10 patients with Broca's aphasia demonstrated that the advantage for producing the past tense of irregular over regular verbs exhibited by these patients was eliminated when the two sets of past-tense forms were matched for phonological complexity (Bird, Lambon Ralph, Seidenberg, McClelland, & Patterson, 2003). The interpretation given was that a generalised phonological impairment was central to the patients' language deficits, including their poor performance on regular past tense verbs. The current paper provides further evidence in favour of this hypothesis, on the basis of a detailed analysis of the errors produced by these same 10 patients in reading, repetition, and sentence completion for a large number of regular, irregular, and nonce verbs. The patients' predominant error types in all tasks and for all verb types were close and distant phonologically related responses. The balance between close and distant errors varied along three continua: the severity of the patient (more distant errors produced by the more severely impaired patients); the difficulty of the task (more distant errors in sentence completion>reading>repetition); the difficulty of the item (more distant errors for novel word forms than real verbs). A position analysis for these phonologically related errors revealed that vowels were most likely to be preserved and that consonant onsets and offsets were equally likely to be incorrect. Critically, the patients' errors exhibited a strong tendency to simplify the phonological form of the target. These results are consistent with the notion that the patients' relatively greater difficulty with regular past tenses reflects a phonological impairment that is sensitive to the complexity of spoken forms.     

Selective spatial processing deficits in an at-risk subgroup of the fragile X premutation

Until a decade ago, it was assumed that males with the fragile X premutation were unaffected by any cognitive phenotype. Here we examined the extent to which CGG repeat toxicity extends to visuospatial functioning in male fragile X premutation carriers who are asymptomatic for a late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). Thirty-three premutation males aged 20-68 years [divided into two groups: 16 low-repeat carriers (CGG ≥ 55 ≤ 100) and 17 high-repeat carriers (CGG>100)] with a family history of fragile X syndrome and 62 non-affected adult males with normal FMR1 alleles were recruited. Subjects underwent neuropsychological tests of visuospatial and visual working memory functioning and visuoperceptual processing. On measures of visuospatial processing, the high-repeat carriers performed significantly worse than the normal allele group when age and IQ were covaried out. With increasing age and only in carriers of a larger (>100 repeats) premutation allele was there a greater decrement in visuospatial working memory functioning. Performance on spatial and perceptual judgement tasks failed to show similar specificity in males within the upper premutation range. We conclude that identification of selective visuospatial impairments in carriers of a larger premutation allele indicates greater CGG repeat toxicity in specific neural regions. Longitudinal follow-up studies will be needed to determine whether subtle decline in visuospatial functioning is associated with the later onset of motor symptoms of FXTAS.