Progressive anomia with preserved oral spelling and automatic speech

We report a patient, Newton, with a progressive classical anomia resulting from focal degeneration of the left hemisphere. In naming tasks Newton spelt aloud picture names that he could not retrieve, indicating a dissociation between orthography and phonology. Unusually, his writing and letter-pointing performance were impaired and spelling was achieved only through alphabet recitation. A study of automatic speech tasks demonstrated strikingly preserved naming performance on automatic compared to nominative tasks. We argue that automatic tasks provide phonological cues that facilitate phonological activation. With progression of disease Newton has shown increasing difficulty reading and repeating words, which we interpret in terms of a progressive elevation in the threshold for activation of phonology. Phonological cueing of picture names has yielded superior naming than word reading and even repetition, a finding consistent with the notion that task characteristics influence likelihood of phonological activation and naming success, but contrary to the notion that there exist separate task-specific output systems. We conclude that Newton exhibits a unique pattern of deficits, which have theoretical relevance for the debate on the relationship between phonology and orthography, the role of automatic speech and the relationship between naming, reading and repetition.     

Sparing of country names in the context of phonological impairment

Many single case studies have reported selective impairment of proper or common names in anomic speakers, providing evidence for a categorical organisation of the lexical-semantic network. These dissociations have been observed in oral and/or written naming and sometimes in comprehension. Here we report the case of an aphasic patient with severely impaired phonological encoding presenting a dissociation between proper and common names. Superior production of countries and nationalities was observed in all output tasks (naming, reading and repetition). The interest of a preservation of proper name categories in the context of phonological impairment lies in the question of the propagation of categorical organisation to the processes of phonological encoding. We suggest that the observed dissociation can be explained by relative sparing of countries and nationalities at lexical-semantic level as in previous reported cases and that this organisation spreads beyond lexical selection, to phonological encoding.     

The natural history of late-stage "pure" semantic dementia

Relatively little is known about the neuropsychological profile of late-stage semantic dementia. This article provides a detailed assessment of patient MK who, despite her very severe semantic impairments, remained cooperative to testing and, unusually, did not show additional behavioral/personality changes. Although MK's initial presentation was typical of semantic dementia (SD), her performance began to deviate from the normal pattern. She developed impairments of single word repetition and regular word reading, and began to produce phonological errors in picture naming and spontaneous speech. These deficits might suggest that late-stage SD includes an independent disorder of phonology. An alternative possibility, however, is that phonological processing cannot proceed normally in the face of profound semantic degradation. A series of experiments supported the latter explanation of MK's deficits. In picture naming, MK showed little effect of progressive phonological cueing, did not reveal an increased sensitivity to word length or phonological complexity and continued to show a high degree of item-specific consistency in both accuracy and errors: she tended to produce the same erroneous phonemes for each item. She remained sensitive to the effects of phonological similarity in immediate serial recall. Letter substitution errors in regular word reading were more common for lower frequency letters (e.g., Q, Z). These letters also produced more item errors in immediate serial recall, suggesting that a frequency-graded loss of letter knowledge, rather than separate orthographic and phonological deficits, accounted for the deficits in both of these tasks. These findings are discussed in terms of theories that posit strong interactivity between phonology and semantics.     

Do deep dyslexia, dysphasia and dysgraphia share a common phonological impairment?

This study directly compared four patients who, to varying degrees, showed the characteristics of deep dyslexia, dysphasia and/or dysgraphia--i.e., they made semantic errors in oral reading, repetition and/or spelling to dictation. The "primary systems" hypothesis proposes that these different conditions result from severe impairment to a common phonological system, rather than damage to task-specific mechanisms (i.e. grapheme-phoneme conversion). By this view, deep dyslexic/dysphasic patients should show overlapping deficits but previous studies have not directly compared them. All four patients in the current study showed poor phonological production across different tasks, including repetition, reading aloud and spoken picture naming, in line with the primary systems hypothesis. They also showed severe deficits in tasks that required the manipulation of phonology, such as phoneme addition and deletion. Some of the characteristics of the deep syndromes - namely lexicality and imageability effects - were typically observed in all of the tasks, regardless of whether semantic errors occurred or not, suggesting that the patients' phonological deficits impacted on repetition, reading aloud and spelling to dictation in similar ways. Differences between the syndromes were accounted for by variation in other primary systems--particularly auditory processing. Deep dysphasic symptoms occurred when the impact of phonological input on spoken output was disrupted or reduced, either as a result of auditory/phonological impairment, or for patients with good phonological input analysis, when repetition was delayed. 'Deep' disorders of reading aloud, repetition and spelling can therefore be explained in terms of damage to interacting primary systems such as phonology, semantics and vision, with phonology playing a critical role.     

Examining the neural and cognitive processes that underlie reading through naming speed tasks

We combined fMRI with eye tracking and speech recording to examine the neural and cognitive mechanisms that underlie reading. To simplify the study of the complex processes involved during reading, we used naming speed (NS) tasks (also known as rapid automatized naming or RAN) as a focus for this study, in which average reading right‐handed adults named sets of stimuli (letters or objects) as quickly and accurately as possible. Due to the possibility of spoken output during fMRI studies creating motion artifacts, we employed both an overt session and a covert session. When comparing the two sessions, there were no significant differences in behavioral performance, sensorimotor activation (except for regions involved in the motor aspects of speech production) or activation in regions within the left‐hemisphere‐dominant neural reading network. This established that differences found between the tasks within the reading network were not attributed to speech production motion artifacts or sensorimotor processes. Both behavioral and neuroimaging measures showed that letter naming was a more automatic and efficient task than object naming. Furthermore, specific manipulations to the NS tasks to make the stimuli more visually and/or phonologically similar differentially activated the reading network in the left hemisphere associated with phonological, orthographic and orthographic‐to‐phonological processing, but not articulatory/motor processing related to speech production. These findings further our understanding of the underlying neural processes that support reading by examining how activation within the reading network differs with both task performance and task characteristics.     

The interaction between orthographic and phonological information in children: an fMRI study

We examined the neural representations of orthographic and phonological processing in children, while manipulating the consistency between orthographic and phonological information. Participants, aged 9-15, were scanned while performing rhyming and spelling judgments on pairs of visually presented words. The orthographic and phonological similarity between words in the pair was independently manipulated, resulting in four conditions. In the nonconflicting conditions, both orthography and phonology of the words were either (1) similar (lime-dime) or (2) different (staff-gain); in conflicting conditions, words had (3) similar phonology and different orthography (jazz-has) or (4) different phonology and similar orthography (pint-mint). The comparison between tasks resulted in greater activation for the rhyming task in bilateral inferior frontal gyri (BA 45/47), and greater activation for the spelling task in bilateral inferior/superior parietal lobules (BA 40/7), suggesting greater involvement of phonological and semantic processing in the rhyming task, and nonlinguistic spatial processing in the spelling task. Conflicting conditions were more difficult in both tasks and resulted in greater activation in the above regions. The results suggest that when children encounter inconsistency between orthographic and phonological information they show greater engagement of both orthographic and phonological processing.     

Case Study Impairment to phonological processes in a Cantonese‐speaking brain‐damaged patient

Background: Previous studies have shown that brain‐damaged patients with selective deficits to phonological processes produced frequent phonological errors and similar error patterns in all spoken tasks, exhibited the effects of word frequency, grammatical class, and imageability, and were unable to make rhyming judgements, due to impaired lexical retrieval and/or phonological representations. Aims: This paper describes a Cantonese‐speaking brain‐damaged patient, LKK, whose performance patterns in spoken tasks indicate impairment to both the lexically mediated non‐semantic and semantic pathways of oral production, as well as the phonological output buffer. Methods & Procedures: A range of tasks was conducted including repetition, reading aloud, oral naming, written/spoken word–picture matching, non‐verbal semantic tests, written lexical decision, and homophone judgements. Outcomes & Results: LKK performed normally on written lexical decision, word–picture matching, and non‐verbal semantic tests, but he was unable to make homophone judgements and showed impaired production in all oral tasks. He was better able to read aloud names of objects than to name them. He also made more semantic errors in naming than reading. His accuracy in reading single words was affected by word frequency and form class. Further observations of his oral production included better (but nevertheless impaired) performance on repetition than reading and naming, a consistent effect of word length across tasks, and a tendency for phonological errors to occur on the coda compared with the onset. Conclusions: There was sufficient evidence for deficits of the phonological lexicon and/or the access to it along the non‐semantic route and the semantic pathway at the post‐semantic level in LKK. The effect of word length and comparable patterns of error distribution across spoken tasks suggested additional impairment to the phonological output buffer. The different levels of accuracy in repetition, reading, and naming, as well as the differential rates of semantic errors in these tasks were consistent with predictions of the summation hypothesis.     

Combining treatment for written and spoken naming.

Individuals with left-hemisphere damage often have concomitant impairment of spoken and written language. Whereas some treatment studies have shown that reading paired with spoken naming can benefit both language modalities, little systematic research has been directed toward the treatment of spelling combined with spoken naming. The purpose of this study was to examine the therapeutic effect of pairing a lexical spelling treatment referred to as Copy and Recall Treatment (CART) with verbal repetition of target words. This approach (CART + Repetition) was compared with treatment using verbal repetition without the inclusion of orthographic training (Repetition Only). Two individuals with moderate aphasia and severe impairment of spelling participated in the study using a multiple baseline design across stimulus sets and treatment conditions. Both participants improved spelling of targeted words as well as spoken naming of those items, but improvement in spoken naming was marked for one individual in the CART + Repetition condition, while the other participant made smaller gains in spoken than written naming irrespective of treatment condition. Consideration of the participant profiles suggested that CART + Repetition provides greater benefit when there is some residual phonological ability and the treatment serves to stimulate links between orthography and phonology.     

Lexical access via letter naming in a profoundly alexic and anomic patient: a treatment study.

We report the results of a letter naming treatment designed to facilitate letter-by-letter reading in an aphasic patient with no reading ability. Patient M.R.'s anomia for written letters reflected two loci of impairment within visual naming: impaired letter activation from print (a deficit commonly seen in pure alexic patients who read letter by letter) and impaired access to phonology via semantics (documented in a severe multimodality anomia). Remarkably, M.R. retained an excellent ability to pronounce orally spelled words, demonstrating that abstract letter identities could be activated normally via spoken letter names, and also that lexical phonological representations were intact when accessed via spoken letter names. M.R.'s training in oral naming of written letters resulted in significant improvement in her oral naming of trained letters. Importantly, as M.R.'s letter naming improved, she became able to employ letter-by-letter reading as a compensatory strategy for oral word reading. M.R.'s success in letter naming and letter-by-letter reading suggests that other patients with a similar pattern of spared and impaired cognitive abilities may benefit from a similar treatment. Moreover, this study highlights the value of testing the pronunciation of orally spelled words in localizing the source of prelexical reading impairment and in predicting the functional outcome of treatment for impaired letter activation in reading.     

Independent access to phonological and orthographic lexical representations: a replication study

Traditionally, it has been assumed that written abilities are completely dependent on phonology (the so-called phonological mediation theory). In this view, the semantic system activates the phonological form of a word, which then activates the corresponding orthographic representation. This hypothesis predicts that in double naming tasks (two temporally close responses to the same picture in the two output modalities), the word selected for a written response will always correspond to the one selected for a spoken output. On the contrary,the orthographic autonomy theory hypothesises the independence of the written output lexicon, which, in the presence of severe damage to conversion procedures, could be directly activated from the semantic system. In this case, the theory predicts that double naming tasks give rise to lexically inconsistent responses.We describe a non-fluent aphasic patient, RA, with agrammatic speech and severe word- finding difficulties. He also presented with severe damage to the phonology-to-orthography and orthography-to-phonology conversion procedures. His performance on picture naming tasks was significantly worse in the spoken than in the written output modality. Errors were predominantly omissions. Few semantic paraphasias were present. Semantic errors did not arise from a deficit in the semantic system since the patient performed flawlessly on a semantic questionnaire and a word picture matching task and gave correct definitions of the items. Although not predicted by the phonological mediation theory, on double naming tasks the patient gave inconsistent responses (i.e. he correctly wrote the stimulus "z-e-b-r-a" but he orally produced "giraffe"). Taken together, these results further confirm the hypothesis that access to the orthographic form of words can be accomplished independently, without the mediation of phonology (the orthographic autonomy hypothesis).     

The left posterior superior temporal gyrus participates specifically in accessing lexical phonology

Impairments in phonological processing have been associated with damage to the region of the left posterior superior temporal gyrus (pSTG), but the extent to which this area supports phonological processing, independent of semantic processing, is less clear. We used repetition priming and neural repetition suppression during functional magnetic resonance imaging (fMRI) in an auditory pseudoword repetition task as a semantics-free model of lexical (whole-word) phonological access. Across six repetitions, we observed repetition priming in terms of decreased reaction time and repetition suppression in terms of reduced neural activity. An additional analysis aimed at sublexical phonology did not show significant effects in the areas where repetition suppression was observed. To test if these areas were relevant to real word production, we performed a conjunction analysis with data from a separate fMRI experiment which manipulated word frequency (a putative index of lexical phonological access) in picture naming. The left pSTG demonstrated significant effects independently in both experiments, suggesting that this area participates specifically in accessing lexical phonology.     

Independent Access to Phonological and Orthographic Lexical Representations: A Replication Study

Abstract

Traditionally, it has been assumed that written abilities are completely dependent on phonology (the so-called phonological mediation theory). In this view, the semantic system activates the phonological form of a word, which then activates the corresponding orthographic representation. This hypothesis predicts that in double naming tasks (two temporally close responses to the same picture in the two output modalities), the word selected for a written response will always correspond to the one selected for a spoken output. On the contrary, the orthographic autonomy theory hypothesises the independence of the written output lexicon, which, in the presence of severe damage to conversion procedures, could be directly activated from the semantic system. In this case, the theory predicts that double naming tasks give rise to lexically inconsistent responses.

We describe a non-fluent aphasic patient, RA, with agrammatic speech and severe word- finding difficulties. He also presented with severe damage to the phonology-to-orthography and orthography-to-phonology conversion procedures. His performance on picture naming tasks was significantly worse in the spoken than in the written output modality. Errors were predominantly omissions. Few semantic paraphasias were present. Semantic errors did not arise from a deficit in the semantic system since the patient performed flawlessly on a semantic questionnaire and a word picture matching task and gave correct definitions of the items. Although not predicted by the phonological mediation theory, on double naming tasks the patient gave inconsistent responses (i.e. he correctly wrote the stimulus “z-e-b-r-a” but he orally produced “giraffe”). Taken together, these results further confirm the hypothesis that access to the orthographic form of words can be accomplished independently, without the mediation of phonology (the orthographic autonomy hypothesis).     

Progressive anomia revisited: focal degeneration associated with progranulin gene mutation

In 2003 we reported a case study of a patient, Newton who presented with a progressive circumscribed anomia in association with focal left hemisphere atrophy. Remarkably, he could spell aloud the names of objects that he could not name, indicating dissociated access to phonology and orthography. We now present follow-up clinical data, post-mortem histopathological findings, and results of molecular genetic analysis. Newton showed tau-negative ubiquitin-positive histology consistent with frontotemporal lobar degeneration (FTLD) and a mutation in the progranulin (PGRN) gene. The case exemplifies the heterogeneity of clinical expression of FTLD and contributes to understanding of primary progressive aphasia.     

Progressive Anomia Revisited: Focal Degeneration Associated with Progranulin Gene Mutation

In 2003 we reported a case study of a patient, Newton who presented with a progressive circumscribed anomia in association with focal left hemisphere atrophy. Remarkably, he could spell aloud the names of objects that he could not name, indicating dissociated access to phonology and orthography. We now present follow-up clinical data, post-mortem histopathological findings, and results of molecular genetic analysis. Newton showed tau-negative ubiquitin-positive histology consistent with frontotemporal lobar degeneration (FTLD) and a mutation in the progranulin (PGRN) gene. The case exemplifies the heterogeneity of clinical expression of FTLD and contributes to understanding of primary progressive aphasia.     

Electrophysiological estimates of the time course of semantic and phonological encoding during listening and naming

Current psycholinguistic models suggest that we know what we want to say before we decide how we are going to say it: in other words, for speaking, word meaning is activated prior to information about syntax and phonology. Listening likely involves the reverse order of processes: phonological processing before meaning activation. We examined the relative time courses of phonological and semantic processing during language production and comprehension using event-related brain potentials (ERPs). Participants viewed a series of pictures (with the instruction to covertly name the depicted item), or heard a series of words, and made dual choice Go/noGo decisions based on each item's conceptual (whether the item was an animal or an object) and phonological features (whether the item's German name started with a vowel or a consonant). During picture naming, the N200 component (related to response inhibition) indicated that conceptual processing preceded phonological processing by about 170ms. During auditory word processing, on the other hand, the brain activity related to these two aspects of comprehension indicated some temporal overlap with the N200 to phonological processing preceding that to semantic processing by only about 85ms. In sum, the data are compatible with current psycholinguistic models of speech production and comprehension and argue for serial or widely spaced cascaded processing during production but more parallel processing of information during comprehension.     

Jargon dyslexia in an individual with semantic dementia: further evidence for task-specificity in phonological output

We report a patient with semantic dementia who demonstrated a very unusual dyslexia. He had a global loss of conceptual knowledge in the context of a fluent dysphasia and intact syntax. However, he did not have the surface dyslexia which is typical of semantic dementia; rather his reading impairment was characterized by speech production errors resulting in multiple neologisms. In a series of experiments it was established that input phonological and input orthographical processing were intact as was output phonology for naming and propositional speech. We demonstrate that our patient has a task-specific phonological deficit and we argue that reading and propositional speech rely upon dissociable phonological output systems. Thus we corroborate our earlier evidence of task-specific phonological output stores (Crutch and Warrington, 2001). We also document a greater difficulty with comprehending the written than the spoken word. We account for this pattern of performance in terms of our patient's attempting to read by the indirect phonological route, as with other semantic dementia patients, but suggest that this process is overridden by the task-specific speech production deficit.     

Dissociated roles of the middle frontal gyri in the processing of Chinese characters

The present study examined a hypothesis that the right middle frontal gyrus participates in processing orthography of Chinese characters, while the left middle frontal gyrus mediates access to phonology and semantics. Brain activation during three character tasks, which required processing orthography, phonology, or semantics of Chinese characters, respectively, was measured by functional magnetic resonance imaging. Comparable neural activity in the right middle frontal gyrus was observed in all three character tasks that always demand orthographical processing. In contrast, the left middle frontal gyrus showed greater activation in the phonological and semantic tasks than in the orthographic task. These results suggest that the right and left middle frontal gyrus have dissociable functions in achieving Chinese character recognition.     

The consequences of progressive phonological impairment for reading aloud

The ‘primary systems’ view of reading disorders proposes that there are no neural regions devoted exclusively to reading, and therefore that acquired dyslexias should reliably co-occur with deficits in more general underlying capacities. This perspective predicted that surface dyslexia, a selective deficit in reading aloud ‘exception’ words (those with atypical spelling-sound characteristics), should be a consistent feature of semantic dementia, a progressive disorder of conceptual knowledge, and just such a pattern has been observed in previous research. In a similar vein, one might expect the gradual deterioration of phonological processing seen in the nonfluent forms of progressive aphasia to be accompanied by phonological dyslexia, a selective deficit in reading of unfamiliar letter strings, i.e., nonwords. The present study, reporting a case-series consideration of reading-aloud data from 16 progressive nonfluent aphasic patients, revealed a pattern in which both low-frequency exception word and nonword reading were comparably compromised. The severity of the reading disorder was predicted by scores on the expressive language task of picture naming but not the receptive task of spoken word-to-picture matching. Our hypothesis that a phonological deficit underpins diminished performance for both naming and reading was supported by the finding that reading-aloud performance was predicted specifically by the rate of phonological errors in picture naming. Moreover, the strength of this relationship was similar for low-frequency exception words and nonwords, suggesting that reading deficits for these two types of items in this disorder shared a common cause: a progressive impairment of phonological processing.