Semantic capacities of the right hemisphere as seen in two cases of pure word blindness.

Two patients with pure alexia were studied with tachistoscopically presented stimuli to examine factors influencing their ability to distinguish words from nonwords and to derive semantic information at exposures too brief for explicit letter identification. Both patients had profound right hemianopia and computerized tomography (CT) evidence of splenial destruction. Both patients were successful in making word/nonword decisions for high-frequency, but not low-frequency, words. They could judge semantic class membership reliably for such common categories as animals and vegetables, but not for arbitrarily selected categories, such as office-related items. Judgments about the gender of people's names and place versus person name distinctions were made with high reliability. Results are interpreted as evidence for limited word recognition and semantic-processing capacity in the right hemisphere.

Effects of age and hearing sensitivity on the use of prosodic information in spoken word recognition.

It is well known that spoken words can often be recognized from just their onsets and that older adults require a greater word onset duration for recognition than young adults. In this study, young and older adults heard either just word onsets, word onsets followed by white noise indicating the full duration of the target word, or word onsets followed by a low-pass-filtered signal that indicated the number of syllables and syllabic stress (word prosody) in the absence of segmental information. Older adults required longer stimulus durations for word recognition under all conditions, with age differences in hearing sensitivity contributing significantly to this age difference. Within this difference, however, word recognition was facilitated by knowledge of word prosody to the same degree for young and older adults. These findings suggest, first, that listeners can detect and utilize word stress in making perceptual judgments and, second, that this ability remains spared in normal aging.

The role of prosody in the mental lexicon.

Current models of spoken word recognition take into account factors such as word frequency, word onset cohort size, and phonological neighborhood density. Using the word onset gating technique we tested word recognition when bandpass filtering was used to allow subjects to hear the full prosodic pattern of a word (number of syllables and syllabic stress), deprived of segmental information beyond that contained in the onset gate. Subjects also heard either word onsets plus duration information or only word onsets. Results suggest that word prosody is represented in the mental lexicon and is effectively used by listeners in spoken word recognition.

Decision latencies for phonological and semantic information in object identification.

Several on-line studies in the literature have been cited in support of a two-stage model of name-retrieval in which semantic processing precedes and mediates access to phonology. Because of inconsistencies in prior studies an off-line experiment was designed to provide converging evidence on this issue. An experiment is reported in which young and elderly adults were required to give speeded judgments of whether a pictured object matched a named category, a named physical attribute, or a rhyming cue. Latencies for the young adults were fastest for category judgments and slowest for rhyming judgments. For the elderly adults physical attributes and rhyming judgments were equivalent. Results are discussed in terms of "lemma" theory in object naming.

A cross-linguistic study of grammatical morphology in Spanish- and English-speaking agrammatic patients.

To account for cross-linguistic differences in agrammatism, Bates and her colleagues have employed the Competition Model, proposing that the cue validity and cue costs of a grammatical morpheme in a particular language will directly affect how agrammatism is manifested. Using Goodglass et al.'s (1993) Morphosyntax Battery in English and a translated version in Spanish, we analyzed the use of equivalent grammatical structures in production and comprehension by agrammatic speakers of the two languages. Wilcoxon signed-rank tests revealed that the relative order of difficulty in both production and comprehension of various grammatical morphemes was the same for both Spanish- and English-speaking agrammatic patients, with two exceptions (1) the Spanish-speaking agrammatics were relatively better at producing subject-verb agreement, and (2) the Spanish speakers were significantly worse at comprehending both active and passive voice sentences. The Competition Model can explain the performance differences regarding subject-verb agreement and comprehension of active voice sentences, but it cannot account for the differences seen in comprehending passive voice sentences.

The boston corpus of aphasic naming errors.

This report provides verbatim error responses to picture naming given by 30 aphasic patients (10 Broca's aphasics, 6 Wernicke's aphasics, 7 conduction aphasics, and 7 anomic aphasics). The error corpus is intended to supply a rich set of raw data for investigators interested in the characteristics of aphasic word-finding problems as well as those interested in general models of lexical retrieval.

The changing relationship between anatomic and cognitive explanation in the neuropsychology of language.

Changing trends in the approach to neurolinguistics are reviewed. We suggest that these trends are marked by a distinct convergence between linguistic/cognitive and anatomic/physiological approaches to the study of aphasia. With respect to the former, we cite the refinement of analysis of language symptoms and the introduction of experimental methods that reveal real-time aspects of language processing. With respect to the latter, we cite the technical advances in static and dynamic brain imaging that have allowed the in vivo analysis of lesion sites in aphasic patients, and the identification of foci of metabolic activity during linguistic/cognitive tasks in normal brains. We cite recent imaging studies of category-specific lexical dissociations as examples of the productive convergence of anatomic and technological advances to illuminate a particularly challenging problem.

The importance of word-initial phonology: error patterns in prolonged naming efforts by aphasic patients.

Whether multiple conscious efforts at word search bring a subject closer to an elusive word and to eventual successful retrieval remains a subject of debate. Previous work with normal participants has shown that multiple attempts eventuating in correct retrieval are not usually associated with a systematic progression toward target word phonology in the intervening attempts. In this study we analyzed the naming errors produced by 30 aphasic patients who had received the Boston Naming Test. The analyses were designed to elucidate the characteristics of responses that led to eventual success. Our data showed that among aphasics, as with normal subjects, the presence of target-initial phonology in the subject's first response was the most important predictor of correct retrieval. Moreover, progression towards target phonology in the course of multiple attempts was unrelated to eventual correct retrieval.

Judgments of concept similarity by normal and aphasic subjects: relation to naming and comprehension.

A study was conducted in which aphasic patients, age-matched normals, and normal young adults performed five types of matching judgments for object pictures. These required matching for physical identity, basic object identity, and membership in the same superordinate category. Spoken name-to-picture matching was tested for the last two conditions. An analogous set of conditions was presented for letters. Latency patterns across the conditions showed general slowing for the aphasic patients, but with a differential decrement in the conditions that involved auditory (spoken name) input for the matching task. Results showed that variations in semantic judgment capability among the aphasics did not predict the patients' object naming ability.

Agrammatism in aphasiology.

Agrammatism is a pattern of syntactically defective speech that is frequently observed as a prominent feature in Broca's aphasia. It may range in severity from one-word utterances, completely lacking in grammatical organization, to mildly 'telegraphic' speech. First described in the early 19th century, it was originally interpreted by Pick as being due to economy of effort in finding words. Beginning with Jakobson, in 1956, there have been a succession of efforts to give an account of it in terms of linguistic theory. While the theories are still controversial, they have led to much more detailed and systematic description of the linguistic output in agrammatic speech. Cross linguistic comparisons have revealed that the features of agrammatism are not fixed, but are conditioned by the grammatical structure of the speaker's language.

Deterioration of generic knowledge in patients with Alzheimer's disease: evidence from the Number Information Test.

Semantic memory for generic knowledge was assessed in patients with probable Alzheimer's disease (AD; n = 142) and elderly normal control (NC; n = 78) subjects using the Number Information Test (NIT), a test that consists of 24 general knowledge questions that require a single number for an answer (e.g., "How many days are in a year?"). The results showed that patients with AD were impaired, even in the mildest stage of dementia, and that this impairment grew as the severity of their dementia increased over time. In addition, patients with AD were highly consistent in the individual items they missed in subsequent test sessions conducted 1 or 2 years later. These results indicate that semantic memory for generic knowledge is impaired relatively early in AD, deteriorates throughout the course of the disease, and may be due to a loss of knowledge rather than to a retrieval deficit.

Preserved semantic priming effect in alexia.

BH, a left-handed patient with alexia and nonfluent aphasia, was presented with a lexical-decision task in which words and pronounceable pseudowords were preceded by semantically related or unrelated picture primes (Experiment 1). In Experiment 2, BH was given an explicit reading task using the word lists from Experiment 1. Performance on Experiment 2 disclosed severe reading deficits in both oral reading and semantic matching of the words to pictures. However, in Experiment 1, BH demonstrated a significant semantic priming effect, responding more accurately and more quickly to words preceded by related primes than by unrelated primes. The present results suggest that even in a patient with severe alexia, implicit access to semantic information can be preserved in the absence of explicit identification. The possibility of categorical gradient in implicit activation (living vs. nonliving) in BH was also discussed, which, however, needs to be clarified in the further investigation.

Selective preservation of a lexical category in aphasia: dissociations in comprehension of body parts and geographical place names following focal brain lesion.

The selective dissociation of memory for proper names is discussed in the context of a review of dissociations involving broadly defined vs narrowly defined semantic categories in brain damaged adults. Two narrowly defined categories for which dissociations have been reported are body parts (selectively impaired in comprehension) and geographical place names (selectively preserved in comprehension). In this study, 167 aphasic patients were tested for their ability to correctly identify body parts and map locations from spoken names, relative to a baseline for correct responses on general word discrimination (object identification). Wernicke's aphasics and Global aphasics both had significantly more success in pointing to named map locations and significantly worse performance in pointing to named body parts than they had in selecting other objects from multiple choice. Anomic aphasics showed precisely the opposite pattern of results. Other aphasic subgroups (Broca's aphasics, Mixed Nonfluent aphasics, Conduction aphasics, Transcortical Motor and Transcortical Sensory aphasics, and Mixed Fluent aphasics) did not show significant deviations in either direction. We suggest that the selective preservation for place names may be related to their status as proper names.

Comparison of morphology and syntax in free narrative and structured tests: fluent vs. nonfluent aphasics.

Seven agrammatic Broca's and seven paragrammatic conduction aphasics were evaluated on a free narrative story elicitation test and on a structured, cross-modal morphology and syntax battery (MSB). The latter permitted comparison of the same set of morphosyntactic forms in both production and comprehension. Results suggests distinctive oral production profiles, with agrammatics inferior to paragrammatics in use of auxiliaries, verb inflection and passive word order. Only agrammatics commonly omitted articles or main verbs. The use of noun plurals and possessives did not discriminate between the groups. The two groups did not differ in level of performance on MSB comprehension subtests, and the order of difficulty among the comprehension subtests was unrelated to their difficulty for production. This suggests that the source of agrammatic production errors is independent of comprehension errors. The production of targeted constructions on the MSB, an easily scored instrument, closely paralleled production in free narrative.

Pantomime, praxis, and aphasia.

The production and comprehension of pantomimed movements by asphasic subjects were studied with respect to their relationship to the aphasic deficit on one hand and apraxia on the other. At issue was whether impaired use of pantomime is a manifestation of reduced symbolic capacity or purely a manifestation of an apraxic impairment of purposeful movement or both. Tests of pantomime included a Pantomime Recognition Test, a nonverbal Transitive Pantomime Production Test, and an Intransitive Pantomime Production Test (to oral command). Imitation of Nonmeaningful Movements served as a measure of apraxia, uncontaminated by symbolic or linguistic factors. Imitation of Meaningful Movements taken from the pantomime tasks was also tested. Independent measures of auditory comprehension, picture naming, and reading comprehension were used as indices of language impairment. Intellectual function was measured by the Performance scale of the WAIS. Thirty aphasic subjects were examined. Twenty healthy age-matched normals served to establish scoring standards for the pantomime tests. Multiple regression analysis revealed significant, independent contributions from both auditory comprehension and imitation of Nonmeaningful Movements to all of the tests of pantomime production and pantomime recognition. All measures of pantomime production and pantomime recognition were strongly intercorrelated. While the three language measures were strongly correlated with each other, auditory comprehension was the only one of them that was significantly and consistently related to the pantomime tests. None was related to the imitation of nonmeaningful movement. The results are taken as indicating (1) that pantomime production and imitation share common factors with both praxis and auditory comprehension; (2) apraxia entails impairment of both production and interpretation of purposeful movements. Possible theoretical accounts for these results are offered.

Idiosyncratic word associations following right hemisphere damage.

Single oral word associations produced by right-hemisphere-damaged (RHD) stroke patients and age-matched healthy controls were analyzed to assess the right-hemisphere contribution to lexical-semantic processes. RHD patients did not differ from normals in terms of response times, in syntactic class of the response word, or in numbers of errors in response to words drawn from different grammatical categories and words differing in imageability/concreteness. Groups also did not differ in the number of high frequency, popular, associations produced. Despite their apparently intact ability to access high-frequency lexical associates, RHD patients, particularly those with frontal-lobe lesions, also sporadically produced lexical responses that were idiosyncratically related or that were totally unrelated to the stimulus word. An attentional disorder is suggested to explain these pragmatically deviant lexical associations.

Effects of word-onset cuing on picture naming in aphasia: a reconsideration.

When an aphasic is unable to name an object, giving the patient the opening sounds of the target name will often trigger the correct response. Eighteen aphasic subjects were tested using a gating paradigm to compare word onset durations necessary to elicit correct names after an initial naming failure with those necessary for recognizing the same words when spoken in isolation with no picture present. Prerecognition errors were also examined. Results suggested that the facilitation of naming found when examiners supply word-onset sound cues may be due in part to a two-stage process consisting of stem-completion followed by matching the picture with the potential name as generated.

Disorders in executive control functions among aphasic and other brain-damaged patients.

Four experimental procedures for assessing disorders of executive control (Nonverbal Continuous Performance, Graphic Pattern Generation, Sequence Generation Test, and Tower of Hanoi) were administered to 22 left-brain-damaged aphasic patients, 19 right-brain-damaged nonaphasic patients, and 49 healthy controls. Aphasic patients with frontal-lobe lesions were significantly more impaired on these tasks than aphasics with retrorolandic or mixed lesions in the left hemisphere. Patients with right-hemisphere lesions, especially those with frontal-lobe lesions, showed even greater impairments on these visual/spatial tasks. The results suggest that aphasics' impairments in executive control are independent of their linguistic and visuospatial deficits and are specific to lesions in left frontal and prefrontal regions. The clinical utility of the experimental procedures is discussed.

Deep dysphasia: analysis of a rare form of repetition disorder.

"Deep dysphasia" is the parallel in repetition to the reading impairment deep dyslexia. Our patient, S.M., showed part of speech, word/nonword, and concreteness effects in repetition, and he made semantic errors, but his oral reading was relatively spared. Further testing indicated that S.M. did not have difficulty perceiving spoken stimuli or deciding their lexical status, but he was deficient at semantically processing spoken words. Moreover, his phonemic memory was severely impaired. We argue that the routes for repetition (lexical and nonlexical) that function without semantic mediation were defective and that deficits in phonemic memory further diminished their effectiveness, since initial phonological encoding of spoken words was not available to guide the output stages of phonological processing. In addition, the semantically mediated route for repetition was unreliable because semantic processing was faulty and S.M. could not accurately label concepts.

Body image and comprehension of body part names.

The relation between awareness of body topology and auditory comprehension of body part names was studied in 22 aphasic subjects. Two nonverbal tasks--human figure drawing and placement of individual body parts in relation to a drawn face--were compared with two auditory tests of body part comprehension. The two nonverbal and the two verbal tasks were closely correlated with each other, but there was no relation involving either of the verbal tests with either of the nonverbal tests. Selection errors in the auditory comprehension tasks were predominantly semantically based and equally distributed between functionally analogous parts and parts related by location on the body.