Distinguishing semantic and lexical word retrieval deficits in people with aphasia

Background: Identifying the point of breakdown in people with aphasia with disorders of word retrieval is not straightforward. Evidence has been sought from: (i) the nature of the errors in naming; (ii) the variables affecting naming accuracy; (iii) the effects of correct and misleading cues; (iv) performance in other word comprehension and production tasks. However, previous research has demonstrated that each of these sources of evidence provides information compatible with more than level of breakdown. Aims: The study investigates whether a combination of information from these sources can provide a coherent account of how word retrieval is breaking down in people with aphasia. Methods & Procedures: Three people with aphasia (JGr, LM, and KS) took part in four experiments. The first investigated the errors made in picture naming and the factors (target word length, imageability, frequency …) affecting naming accuracy. The second experiment investigated the effects of correct phonemic cues and miscues on word retrieval. The third examined the participants' performance in tests of spoken and written word and picture comprehension. The fourth experiment investigated whether the participants had the processing abilities necessary to generate their own phonemic cues in spoken naming from orthographic information. Outcomes & Results: Evidence from these investigations showed different levels of breakdown in the three participants. JGr's naming was characterised by semantic errors, effects of target imageability and familiarity on naming accuracy, improved naming with correct phonemic cues and semantic errors with miscues, and poor performance in word comprehension tasks. This pattern is consistent with a breakdown at a semantic level underlying JGr's difficulty in word retrieval. In contrast, LM shows performance indicating a breakdown in mapping between intact semantic and phonological representations. He makes primarily no response errors in naming and his accuracy is affected only by frequency and familiarity. Correct phonemic cues can improve his naming accuracy to near normal levels, and he makes no semantic errors, although he is slowed by miscues. His word and picture comprehension is intact. KS shows a more complex pattern of impairment. Like JGr, she shows evidence of a semantic impairment: she makes semantic errors in naming, and her accuracy is affected by target imageability. She makes errors in word comprehension and her word retrieval is adversely affected by miscues. There are two unusual features to her performance: her naming accuracy is not improved by initial phoneme cues (despite effects of miscues and more extensive phonemic cues), and she is better at naming pictures with longer names (a “reverse length effect”). Investigations in experiment four show that KS is using orthographic information on the initial letter of names to generate her own phonemic cues; it is concluded that in addition to her semantic deficit she has an impairment in access to lexical phonological representations. Conclusions: We conclude that careful investigation of the performance of people with aphasia across a range of tasks can be used to identify underlying levels of breakdown in word retrieval. However, superficial resemblances between people with aphasia can be misleading.     

Patterns of breakdown in spelling in primary progressive aphasia

Introduction

The objective of this study is to determine which cognitive processes underlying spelling are most affected in the three variants of primary progressive aphasia (PPA): Logopenic variant primary progressive aphasia (lvPPA), Semantic variant primary progressive aphasia (svPPA), and Nonfluent variant primary progressive aphasia (nfvPPA).

Methods

23 PPA patients were administered The Johns Hopkins Dysgraphia Battery to assess spelling. Subtests evaluate for effects of word frequency, concreteness, word length, grammatical word class, lexicality (words vs pseudowords), and “regularity” by controlling for the other variables. Significant effects of each variable were identified with chi square tests. Responses on all spelling to dictation tests were scored by error type. 16 of the 23 subjects also had a high resolution MRI brain scan to identify areas of atrophy.

Results

We identified 4 patterns of spelling that could be explained by damage to one or more cognitive processes underlying spelling. Nine patients (3 unclassifiable, 4 with lvPPA, 2 with svPPA) had dysgraphia explicable by impaired access to lexical representations, with reliance on sublexical phonology-to-orthography conversion (POC). Two patients (with nfvPPA) showed dysgraphia explicable by impaired access to lexical representations and complete disruption of sublexical POC. Seven patients (4 with lvPPA, 1 with svPPA, 2 unclassifiable) showed dysgraphia explicable by impaired access to lexical-semantic representations and/or lexical representations with partially spared sublexical POC mechanisms. Five patients (1 with nfvPPA, 2 with svPPA, 1 with lvPPA, and 1 unclassifiable) showed dysgraphia explicable by impairment of the graphemic buffer.

Conclusions

Any cognitive process underlying spelling can be affected in PPA. Predominance of phonologically plausible errors, more accurate spelling of regular words than irregular words, and more accurate spelling of pseudowords than words (indicating spared POC mechanisms) may indicate a low probability of progression to nfvPPA.     

Anatomic, clinical, and neuropsychological correlates of spelling errors in primary progressive aphasia

This study evaluates spelling errors in the three subtypes of primary progressive aphasia (PPA): agrammatic (PPA-G), logopenic (PPA-L), and semantic (PPA-S). Forty-one PPA patients and 36 age-matched healthy controls were administered a test of spelling. The total number of errors and types of errors in spelling to dictation of regular words, exception words and nonwords, were recorded. Error types were classified based on phonetic plausibility. In the first analysis, scores were evaluated by clinical diagnosis. Errors in spelling exception words and phonetically plausible errors were seen in PPA-S. Conversely, PPA-G was associated with errors in nonword spelling and phonetically implausible errors. In the next analysis, spelling scores were correlated to other neuropsychological language test scores. Significant correlations were found between exception word spelling and measures of naming and single word comprehension. Nonword spelling correlated with tests of grammar and repetition. Global language measures did not correlate significantly with spelling scores, however. Cortical thickness analysis based on MRI showed that atrophy in several language regions of interest were correlated with spelling errors. Atrophy in the left supramarginal gyrus and inferior frontal gyrus (IFG) pars orbitalis correlated with errors in nonword spelling, while thinning in the left temporal pole and fusiform gyrus correlated with errors in exception word spelling. Additionally, phonetically implausible errors in regular word spelling correlated with thinning in the left IFG pars triangularis and pars opercularis. Together, these findings suggest two independent systems for spelling to dictation, one phonetic (phoneme to grapheme conversion), and one lexical (whole word retrieval).     

Acquired mirror writing and reading: evidence for reflected graphemic representations

Mirror writing occurs when individual letters and whole word strings are produced in reverse direction. By analogy, mirror reading refers to the preference to read mirror reversed over normally written words. These phenomena appear rarely after brain damage and offer insight into the nervous system's organization of visual-spatial and visual-motor representations. We present the case of a 51-year-old patient with persistent mirror writing and reading following traumatic brain injury. She preferred to write in the mirror direction with either hand. She drew asymmetric pictures with the same directional bias as normal right-handed subjects, and she did not exhibit left-right confusion regarding other pictures. By contrast, on picture-word matching and lexical decision tasks, she was faster and more accurate with mirrored than normally written words. This pattern of performance suggests that her behavior was not accounted for by reflected motor programs, or by the mirroring of visual-spatial representations in general. Rather, we suggest that her behavior was produced by privileged access to mirrored graphemes. Furthermore, because she seemed better able to read irregular words in mirrored than in normal formats, we suggest that mirrored representations may exist at the whole word level and not simply at the letter level.     

Phonological,lexical, and semantic errors produced by impairment at the output buffer in a Spanish aphasic patient

We present a single case of a right-handed female patient, RH, who was categorized as suffering from conduction aphasia. She presented no articulatory problems during spontaneous speech but made a significant number of phonological paraphasias in naming and repetition tasks. The number of errors increased for long words and pseudowords. This pattern of results points to damage in the “Phonological Output Buffer” (POB) as the basis of this disorder. However, this patient did not make mistakes when reading words and pseudowords aloud, even when we introduced a delay between the presentation of the word and its production to test the working memory resources of the phonological buffer. Furthermore, the patient’s ability to name objects, repeat words, and write to dictation improved with her degree of familiarity with the items. The damage could be situated at the point where phonemes are selected and ordered to produce words. We posit that the deficits observed in this patient, and the differences encountered between her performance and that of others described in the literature, in particular in reading tasks, can be explained by considering POB damage to be gradual in nature. According to this explanation, the performance of patients with damage to the POB will depend on the amount of information provided by the stimulus (word/nonword), the language particularities (regular/irregular), and the nature of the task demands (repetition, writing, naming, or reading).     

Progressive aphasia and surface Alexia in Japanese

Abstract

We report the reading performance of a patient, NK, with selective left-temporal atrophy and progressive aphasia. NK showed surface alexlc reading with the following pattern: flawless oral reading of kana words; a deficit in reading of two-character kanji words that was particularly severe for lower frequency words with an unpredictable correspondence between the component characters and their pronunciations; a predominance of kanji-word reading errors In which characters were assigned pronunciations appropriate to other words containing these characters. These features were predicted and are interpreted on the basis of (a) recent studies of patients with progressive aphasia in English, (b) recent analyses of surface alexia in terms of an interaction between word frequency and neighbourhood-based consistency of spelling-sound correspondences, and (c) characteristics of the Japanese kana and kanji writing systems.     

Effect of number of syllables in word repetition]

We report a case of non-fluent conduction aphasia. The patient was a 59-year-old right-handed male. He suffered from aphasia after a left internal carotid artery occlusion. MRI study revealed subcortical lesions in the left inferior frontal gyrus and cortical lesion in the anterior part of the left insular gyrus and the left postcentral gyrus. The patient showed good comprehension of words and daily conversation but had a common difficulty in the following tasks; naming of pictures, repetition of words, reading of kanji and kana letters. In these tasks, the phonological output of the patient contained many literal paraphasias and there was a tendency that errors appeared more in the posterior portion of a target word. We analyzed the position of errors in the target word on word repetition tasks. The result confirmed the above observation. We speculate that the length of a target word may have played a critical rote in this patient's repetition capability.     

Supplementary motor area aphasia: a case report.

A 72-year-old right-handed woman developed aphasia after a left supplementary motor area (SMA) infarct. She had a right hemiparesis, more paretic on the leg, a tendency to look to her left, and loss of spontaneity. Neuropsychological deficits were mainly in the initiation of language production. She did not speak spontaneously, but responded and articulated well to questions. She named objects correctly when presented, and could repeat words, phrases, and sentences well. She had a difficulty in reading aloud, writing spontaneously and writing to dictation, but preserved the ability to copy written material. This is another rare case of SMA aphasia.     

Gogi (word-meaning) aphasia

Gogi (word meaning) aphasia is an aphasic syndrome originally described by Tsuneo Imura in 1943. According to Imura, this syndrome is characterized by 4 symptoms: (1) difficulty in comprehending the meaning of a word despite perfect perception of the sound of the word; (2) presence of word amnesia and verbal paraphasia; (3) preservation of the ability to repeat spoken words; and (4) characteristic disturbances in reading and writing, in which Kana (Japanese syllabogram) can be correctly read and written, but Kanji (Japanese logogram) is read and transcribed in a peculiar way without comprehension, resulting in strange paragraphia. Gogi aphasia occupies a unique seat in the category of transcortical sensory aphasia. While the latter is grossly defined as fluent sensory aphasia with good repetition and without any specification about the linguistic level of deficit, the former is defined more specifically as fluent sensory aphasia with the deficit limited to the level of words. The characteristic Kana-Kanji dissociation aids in the diagnosis of this syndrome. Recently, it has been repeatedly confirmed that the temporal lobe type of Pick disease (known as semantic dementia in recent English literature) often presents the clinical picture of Gogi aphasia in its early course. Many Japanese physicians have contributed to the elucidation of this clinicopathological correlation. This is mainly because many neurologists and psychiatrists in Japan have long been familiar with the concept of Gogi aphasia and the nosology of Pick disease.     

Neural substrates for writing impairments in Japanese patients with mild Alzheimer's disease: a SPECT study

Language is fairly well preserved in most patients with mild Alzheimer's disease, but writing ability seems to be impaired even in the early stages of the disease. To investigate the neural bases of writing impairments in Alzheimer's disease (AD), we examined the correlation between writing ability and regional cerebral blood flow (rCBF) in 52 Japanese patients with mild AD compared to 22 controls, using single photon emission computed tomography (SPECT). We found that, compared with control subjects, Kana writing to dictation and copying Kanji words were preserved in AD patients, but writing to dictating Kanji words was impaired. We classified the errors in the Kanji dictation task into four types to investigate the correlation between rCBF and the error type, as follows: non-response errors, phonologically plausible errors, non-phonologically plausible errors, and peripheral errors. Non-response errors, which indicated difficulty with retrieving Kanji graphic images, were the most frequent. When controlled for confounding factors, the number of non-response errors negatively correlated with rCBF in the left inferior parietal lobule, the posterior middle and inferior temporal gyri, and the posterior middle frontal gyrus. Thus, the impaired recall of Kanji in early Alzheimer's disease is related to dysfunctional cortical activity, which appears to be predominant in the left frontal, parietal, and temporal regions.     

Lexical spelling in children and adolescents with specific language impairment: Variations with the writing situation

The goal of this study was to compare the lexical spelling performance of children and adolescents with specific language impairment (SLI) in two contrasting writing situations: a dictation of isolated words (a classic evaluative situation) and a narrative of a personal event (a communicative situation). Twenty-four children with SLI and 48 typically developing children participated in the study, split into two age groups: 7–11 and 12–18 years of age. Although participants with SLI made more spelling errors per word than typically developing participants of the same chronological age, there was a smaller difference between the two groups in the narratives than in the dictations. Two of the findings are particularly noteworthy: (1) Between 12 and 18 years of age, in communicative narration, the number of spelling errors of the SLI group was not different from that of the typically developing group. (2) In communicative narration, the participants with SLI did not make specific spelling errors (phonologically unacceptable), contrary to what was shown in the dictation. From an educational perspective or that of a remediation program, it must be stressed that the communicative narration provides children—and especially adolescents—with SLI an opportunity to demonstrate their improved lexical spelling abilities. Furthermore, the results encourage long-term lexical spelling education, as adolescents with SLI continue to show improvement between 12 and 18 years of age.     

The role of speech production in auditory-verbal short-term memory: evidence from progressive fluent aphasia

We report investigations of auditory-verbal short-term memory (AVSTM) in a patient with progressive fluent anomic aphasia. Despite having apparently normal AVSTM as measured by digital span, FM was significantly impaired in immediate serial recall of short sequences of familiar words, and even in reproducing a single word after a filled delay of just a few seconds. In both tasks, unlike normal subjects, she produced numerous phonological errors, often consisting of phonological segments from the intended target word concatenated with segments from other words in the stimulus sequence. Her success in these tasks was modulated (i) consistently by word frequency (high > low), (ii) inconsistently by word imageability (high > low), and (iii) most dramatically by 'nameability': that is, FM was much more likely to reproduce a word correctly in AVSTM if it was a word that she could also produce successfully in picture-naming tasks. On the basis of these and additional experiments designed to exclude other interpretations, we conclude that AVSTM may be crucially supported by activation of the lexical phonological representations responsible for production of content words in speech.     

Impaired spelling in Alzheimer's disease: a linguistic deficit?

Different kinds of real words and pronounceable pseudowords (PWs) were presented for writing to dictation to patients with the diagnosis of probable Alzheimer's disease (AD) and to age- and education-matched healthy controls. Though spelling less accurately on all tasks, AD patients responded in a manner generally qualitatively similar to controls. Except for a slightly enhanced effect of spelling regularity in real word writing accuracy, AD patients showed the same sensitivity to various lexical, orthographic and phonological variables as controls. Both groups showed no difference in spelling accuracy for words and PWs with regular vs ambiguous spelling patterns, and groups also showed similar orthographic preferences when spelling PWs having several different acceptable pronunciations. Finally, AD patients and controls produced similar types of errors when spelling real words. Dementia severity was related to the overall accuracy, but not to the pattern, of spelling responses. It is suggested that the decline in response accuracy in cognitively demanding writing tasks in patients with more advanced dementia is most likely due to semantic impairment and impairments of nonlinguistic functions of attention, executive control and praxis, rather than to a disturbance within language specific processes.     

A case of crossed aphasia with echolalia after the resection of tumor in the right medial frontal lobe]

We report a right-handed woman, who developed a non-fluent aphasia after resection of astrocytoma (grade III) in the right medial frontal lobe. On admission to the rehabilitation department, neurological examination revealed mild left hemiparesis, hyperreflexia on the left side and grasp reflex on the left hand. Neuropsychologically she showed general inattention, non-fluent aphasia, acalculia, constructional disability, and mild buccofacial apraxia. No other apraxia, unilateral spatial neglect or extinction phenomena were observed. An MRI demonstrated resected areas in the right superior frontal gyrus, subcortical region in the right middle frontal gyrus, anterior part of the cingulate gyrus, a part of supplementary motor area. Surrounding area in the right frontal lobe showed diffuse signal change. She demonstrated non-fluent aprosodic speech with word finding difficulty. No phonemic paraphasia, or anarthria was observed. Auditory comprehension was fair with some difficulty in comprehending complex commands. Naming was good, but verbal fluency tests for a category or phonemic cuing was severely impaired. She could repeat words but not sentences. Reading comprehension was disturbed by semantic paralexia and writing words was poor for both Kana (syllabogram) and Kanji(logogram) characters. A significant feature of her speech was mitigated echolalia. In both free conversation and examination setting, she often repeated phrases spoken to her which she used to start her speech. In addition, she repeated words spoken to others which were totally irrelevant to her conversation. She was aware of her echoing, which always embarrassed her. She described her echolalic tendency as a great nuisance. However, once echoing being forbidden, she could not initiate her speech and made incorrect responses after long delay. Thus, her compulsive echolalia helped to start her speech. Only four patients with crossed aphasia demonstrated echolalia in the literature. They showed severe aphasia with markedly decreased speech and severe comprehension deficit. A patient with a similar lesion in the right medial frontal lobe had aspontaneity in general and language function per se could not be examined properly. Echolalia related to the medial frontal lesion in the language dominant hemisphere was described as a compulsive speech response, because some other 'echoing' phenomena or compulsive behavior were also observed in these patients. On the other hand, some patients with a large lesion in the right hemisphere tended to respond to stimuli directed to other patients, so called 'response-to-next-patient-stimulation'. This behavior was explained by disinhibited shift of attention or perseveration of the set. Both compulsive speech responses and 'response-to-next-patient-stimulation' like phenomena may have contributed to the echolalia phenomena of the present case.     

“Are there lexicons?” A study of lexical and semantic processing in word-meaning deafness suggests “yes”

A controversial issue in the cognitive neuroscience of language is the question whether independent lexical representations need to be included in cognitive models. Recent models claim to account for the available data without including phonological or orthographic lexicons. These models base their lexical decision (“Is it a word or not?”) either on familiarity of the input string or alternatively, on semantic information. These two alternatives were evaluated in a series of experiments with an individual suffering from word-meaning deafness. This is a rare disorder of auditory word comprehension which affects mapping of a word’s phonology to its meaning. The participant, BB, was unaffected by the ‘word-likeness’ of nonwords with comparable accuracy for plausible and abstruse nonwords. She was further able to make lexical decisions despite her severe impairment in comprehending the word’s meaning. Lexical and semantic processing were assessed on an item-specific basis providing a methodological advancement over previous studies. The comprehension tasks involved word-picture matching as well as definition tasks. The results suggest that BB’s lexical decisions are based neither on familiarity of the input string nor on semantic information, which was largely unavailable. The only alternative are lexical representations on which she could base her decisions.     

Writing disorders in primary progressive aphasia]

We investigated longitudinally three patients with primary progressive aphasia (PPA) who exhibited fluent aphasia at the early stage, in terms of writing disorders. The writing disorders were the most striking during the aphasia quotient (AQ) was 50-60 for all these patients. The characteristic features were as follows: (i) several types of perseverative errors, especially on spontaneous writing rather than on dictation (ii) confusion between letters and pictures (iii) preserved copying ability and (iv) total loss of writing ability at the final stage. Additionally, through the progression, linguistic level of the perseverative errors changed from sentence to word and finally to phoneme. The results suggest that the fluent type PPA patients have difficulty to recall proper letters and to arrange them in correct order following the writing plan, in addition to disinhibition and lexical stereotyping which were commonly observed in perseverative patients. The results also suggest that their writing disorders seem to be based on difficulty of letter manipulation as symbols.     

Alexia for ideograms: implications for kanji alexia

This study was concerned with a model for kanji reading applicable in a non-Japanese population of aphasics. The experimental task required aphasic subjects to match animals with their footprints, a type of ideogram "reading" requiring no special training. As is true for kanji, footprint reading defects were consistently associated with word reading impairment, but some aphasics with defects in word reading performed normally in footprint reading. All with defects in footprint reading were also impaired in letter recognition or pantomime recognition. One aphasic's pattern of symptoms was quite similar to the rare phenomenon of Gogi aphasia. Implications for kanji alexia are discussed.     

Rapid interactions between lexical semantic and word form analysis during word recognition in context: evidence from ERPs

We used ERPs to investigate the time course of interactions between lexical semantic and sublexical visual word form processing during word recognition. Participants read sentence-embedded pseudowords that orthographically resembled a contextually supported real word (e.g., "She measured the flour so she could bake a ceke…") or did not (e.g., "She measured the flour so she could bake a tont…") along with nonword consonant strings (e.g., "She measured the flour so she could bake a srdt…"). Pseudowords that resembled a contextually supported real word ("ceke") elicited an enhanced positivity at 130 msec (P130), relative to real words (e.g., "She measured the flour so she could bake a cake…"). Pseudowords that did not resemble a plausible real word ("tont") enhanced the N170 component, as did nonword consonant strings ("srdt"). The effect pattern shows that the visual word recognition system is, perhaps, counterintuitively, more rapidly sensitive to minor than to flagrant deviations from contextually predicted inputs. The findings are consistent with rapid interactions between lexical and sublexical representations during word recognition, in which rapid lexical access of a contextually supported word (CAKE) provides top-down excitation of form features ("cake"), highlighting the anomaly of an unexpected word "ceke."     

Episodic and semantic memory after traumatic brain injury in a child]

In an early-life, a memory disturbance affects the learning and school record directly. Furthermore, it may cause the problem of maltreatment or adaptation difficulty for school life. We report a child amnesia caused by a traumatic brain injury when she was 9 years old. We examined her episodic and semantic memory. We developed 3-steps tasks of recognition and recall for the post-accident episodic memory. First, the examiner presented the patient with four words orally including a label of her episode, and asked her to choose one that she felt familiar with (the recognition of the episodic label). Second, if the word she selected was correct, she was required to recall the episode related to the word (the recall of the episode). Third, if she could not recall the episode herself correctly, she was required to choose a correct sentence about the episode (the recognition of the episode). She could not recall episodes correctly, but produced confabulation instead. She showed, however, good recognition of each episode. Furthermore, we performed recognition tests of time, person, and place about the same post-accident episodes, which were poor especially for time. In semantic memory tasks, we examined about kanji characters (ideogram) learned from the first grade to the sixth grade and mathematical knowledge learned from the second grade to the sixth grade at elementary school ("What centimeters is equal to one meter?" or "Tell me the formula of the size of a circle." etc). We found that she showed a retrograde impairment for about one year. For both episodic and semantic memory, she showed an anterograde impairment. Because of the anterograde amnesia she could not acquire new facts, and also showed para-amnesia or confabulation. In a child with brain damage, neuropsychological assessment is important in predicting effect of rehabilitation and recovery of school performance.