Lexical acquisition in progressive aphasia and frontotemporal dementia

Honorific Speech Impairment: A Characteristic Sign of Frontotemporal Dementia

BACKGROUND

Individuals with the behavioral variant of frontotemporal dementia (bvFTD) exhibit various levels of abulia, disinhibition, impaired judgment, and decline in executive function. Empirical evidence has shown that individuals with bvFTD also often exhibit difficulty using honorific speech, which expresses respect to another party or addressee.

OBJECTIVE

To analyze differences in the ability to use honorific speech among individuals with bvFTD, individuals with dementia of the Alzheimer type (AD dementia), and individuals with normal cognition (NC).

METHOD

A total of 53 native Korean speakers (13 bvFTD, 20 AD dementia, and 20 NC) completed an experimental honorific speech task (HST) that involved both expressive and receptive tasks. We analyzed the number of correct responses and error patterns separately for an expressive task and for a receptive task.

RESULTS

The bvFTD group had significantly fewer correct responses on the HST compared with the AD dementia and NC groups. The bvFTD group exhibited more misjudgment errors in identifying nonhonorific speech as honorific speech in the expressive task, and significantly longer response times in the receptive task, than the AD dementia and NC groups. Significant associations were identified between HST scores and cortical atrophy in the temporal and frontotemporal lobes.

CONCLUSION

A decline in the ability to use honorific speech may be a diagnosable behavioral and psychiatric symptom for bvFTD in Korean-speaking individuals. This decline in individuals with bvFTD could be attributed to multiple factors, including social manners (politeness) and impaired social language use ability (pragmatics).

Speech and language impairments in behavioral variant frontotemporal dementia: A systematic review

Although behavioral variant frontotemporal dementia (bvFTD) is classically defined by behavioral and socio-emotional changes, impairments often extend to other cognitive functions. These include early speech and language deficits related to the disease's core neural disruptions. Yet, their scope and clinical relevance remains poorly understood. This systematic review characterizes such disturbances in bvFTD, considering clinically, neuroanatomically, genetically, and neuropathologically defined subgroups. We included 181 experimental studies, with at least 5 bvFTD patients diagnosed using accepted criteria, comparing speech and language outcomes between bvFTD patients and healthy controls or between bvFTD subgroups. Results reveal extensive and heterogeneous deficits across cohorts, with (a) consistent lexico-semantic, reading & writing, and prosodic impairments; (b) inconsistent deficits in motor speech and grammar; and (c) relative preservation of phonological skills. Also, preliminary findings suggest that the severity of speech and language deficits might be associated with global cognitive impairment, predominantly temporal or fronto-temporal atrophy and MAPT mutations (vs C9orf72). Although under-recognized, these impairments contribute to patient characterization and phenotyping, while potentially informing diagnosis and management.

So Many Are "Few," but so Few Are Also "Few" - Reduced Semantic Flexibility in bvFTD Patients

The processing of quantifier words such as "many" or "few" is a complex operation supported by a plastic fronto-parietal network predominantly in the left hemisphere. The internal reference criterion defining a quantifier (e.g., ≥50% for "many") can be modified in a learning paradigm. Most interestingly, changing the criterion for one quantifier also leads to a change in the criterion for the untrained quantifier, i.e., a semantic restructuring effect, which is supported by Broca's region in the left inferior frontal cortex. Here, we applied this paradigm to patients with the behavioral variant of fronto-temporal dementia (bvFTD) because they suffer from loss of cognitive flexibility, reduced ability to process quantities and their values, impaired reinforcement learning, and language comprehension deficits. The question was whether the patients would be able to perform the task, show direct learning of the new quantifier meanings, and exhibit cognitive flexibility in terms of semantic restructuring. Eleven bvFTD patients took part in two behavioral experiments. In Experiment 1, in a first baseline block, each individual's criterion for "many" and "few" was assessed. In block 2, subjects received feedback about their decisions. Contrary to their initial notion, a proportion of 40% yellow circles was reinforced as "many." In block 3, the effect of this training on their judgments of "many" and "few" was re-assessed. The group of bvFTD patients showed a learning effect for the new criterion trained for the quantifier "many," but failed to generalize this criterion shift to the other quantifier "few." Experiment 2 was similar to Experiment 1, but the patients were trained in Block 2 to judge 60% of circles as "few," with no training for "many." Again, there was an average learning effect for the trained quantifier "few" over the entire group, but no generalization to "many." Since the patients were still able to perform the task and showed learning of "many" to direct feedback, the data suggest that the generalization process, rather than initial learning, is more vulnerable to fronto-temporal degeneration.

Regularity and beyond: Impaired production and comprehension of inflectional morphology in semantic dementia

Studies on inflectional morphology in semantic dementia (SD) have focused on the contrast between the regular and the irregular English past-tense. These studies aimed to contrast the claims of single- and dual-mechanism theories. However, both theories can account for impaired production of irregular verbs observed in SD. According to the dual-mechanism theory, this impairment is related to word-retrieval difficulties, while according to single-mechanism theory it is the consequence of semantic impairment. However, authors suggest that it is time to envision a broader role for semantic memory in the production of semantically encoded aspects of inflectional morphology. This study reports the performance of 10 French-speaking patients with SD in three tasks of inflectional morphology. Their performances were compared to those of a group of 20 age-, gender- and education-matched adults without cognitive impairment. Results show that SD patients had difficulties producing tense and person inflection in verbs and pseudo-verbs, whether regular or pseudo-regular. In a second task in which participants were directly exposed to regularity manipulations, SD patients tended to choose a more typical or predictable alternative over a correctly inflected verb. Results of the third task show that their difficulties in producing semantically encoded aspects of inflection, such as tense, are related to difficulties to understand the semantic content conveyed by inflectional morphemes. Overall, these results support the claim that semantic impairment can cause morphological deficits that do not only affect irregular verbs, but that also have impacts on the production and comprehension of semantic information conveyed by inflectional morphemes.

The Language Profile of Behavioral Variant Frontotemporal Dementia

BACKGROUND

The language profile of behavioral variant frontotemporal dementia (bvFTD) remains to be fully defined.

OBJECTIVE

We aimed to quantify the extent of language deficits in this patient group.

METHODS

We assessed a cohort of patients with bvFTD (n = 24) in relation to patients with semantic variant primary progressive aphasia (svPPA; n = 14), nonfluent variant primary progressive aphasia (nfvPPA; n = 18), and healthy age-matched individuals (n = 24) cross-sectionally and longitudinally using a comprehensive battery of language and general neuropsychological tests. Neuroanatomical associations of language performance were assessed using voxel-based morphometry of patients' brain magnetic resonance images.

RESULTS

Relative to healthy controls, and after accounting for nonverbal executive performance, patients with bvFTD showed deficits of noun and verb naming and single word comprehension, diminished spontaneous propositional speech, and deterioration in naming performance over time. Within the bvFTD group, patients with MAPT mutations had more severe impairments of noun naming and single word comprehension than patients with C9orf72 mutations. Overall the bvFTD group had less severe language deficits than patients with PPA, but showed a language profile that was qualitatively similar to svPPA. Neuroanatomical correlates of naming and word comprehension performance in bvFTD were identified predominantly in inferior frontal and antero-inferior temporal cortices within the dominant hemispheric language network.

CONCLUSIONS

bvFTD is associated with a language profile including verbal semantic impairment that warrants further evaluation as a novel biomarker.

Dissociation of explicit and implicit long-term memory consolidation in semantic dementia: a case study

We report a case study of a semantic dementia patient, whose episodic memory consolidation was tested over a 2-month period. The results reveal that despite early retention of information, the patient lost all explicit information of the newly learnt material after 2 weeks. By contrast, he retained implicit word information even after a 4-week delay. These findings highlight the critical time window of 2-4 weeks in which newly learnt information should be re-encoded in rehabilitations studies. The results also indicate that learnt information can be still accessed with implicit retrieval strategies when explicit retrieval fails.

An investigation of semantic similarity judgments about action and non-action verbs in Parkinson's disease: implications for the Embodied Cognition Framework

The Embodied Cognition Framework maintains that understanding actions requires motor simulations subserved in part by premotor and primary motor regions. This hypothesis predicts that disturbances to these regions should impair comprehension of action verbs but not non-action verbs. We evaluated the performances of 10 patients with Parkinson's disease (PD) and 10 normal comparison (NC) participants on a semantic similarity judgment task (SSJT) that included four classes of action verbs and two classes of non-action verbs. The patients were tested both ON and OFF medication. The most salient results involved the accuracies and reaction times (RTs) for the action verbs taken as a whole and the non-action verbs taken as a whole. With respect to accuracies, the patients did not perform significantly worse than the NC participants for either the action verbs or the non-action verbs, regardless of whether they were ON or OFF their medication. And with respect to RTs, although the patients' responses were significantly slower than those of the NC participants for the action verbs, comparable processing delays were also observed for the non-action verbs; moreover, there was again no notable influence of medication. The major dissociation was therefore not between action and non-action verbs, but rather between accuracies (relatively intact) and RTs (relatively delayed). Overall, the data suggest that semantic similarity judgments for both action and non-action verbs are correct but slow in individuals with PD. These results provide new insights about language processing in PD, and they raise important questions about the explanatory scope of the Embodied Cognition Framework.

Phonological learning in semantic dementia

Patients with semantic dementia (SD) have anterior temporal lobe (ATL) atrophy that gives rise to a highly selective deterioration of semantic knowledge. Despite pronounced anomia and poor comprehension of words and pictures, SD patients have well-formed, fluent speech and normal digit span. Given the intimate connection between phonological STM and word learning revealed by both neuropsychological and developmental studies, SD patients might be expected to show good acquisition of new phonological forms, even though their ability to map these onto meanings is impaired. In contradiction of these predictions, a limited amount of previous research has found poor learning of new phonological forms in SD. In a series of experiments, we examined whether SD patient, GE, could learn novel phonological sequences and, if so, under which circumstances. GE showed normal benefits of phonological knowledge in STM (i.e., normal phonotactic frequency and phonological similarity effects) but reduced support from semantic memory (i.e., poor immediate serial recall for semantically degraded words, characterised by frequent item errors). Next, we demonstrated normal learning of serial order information for repeated lists of single-digit number words using the Hebb paradigm: these items were well-understood allowing them to be repeated without frequent item errors. In contrast, patient GE showed little learning of nonsense syllable sequences using the same Hebb paradigm. Detailed analysis revealed that both GE and the controls showed a tendency to learn their own errors as opposed to the target items. Finally, we showed normal learning of phonological sequences for GE when he was prevented from repeating his errors. These findings confirm that the ATL atrophy in SD disrupts phonological processing for semantically degraded words but leaves the phonological architecture intact. Consequently, when item errors are minimised, phonological STM can support the acquisition of new phoneme sequences in patients with SD.

The importance of multiple assessments of object knowledge in semantic dementia: the case of the familiar objects task

Semantic dementia (SD) is characterized by a dramatic loss of conceptual knowledge about the meaning of words and the identity of objects. Previous research has suggested that SD patients' knowledge is differentially influenced by the disease and may decline at different degrees depending on a patient's everyday familiarity with certain items. However, no study has examined (a) semantic knowledge deterioration and (b) the potential significance of autobiographical experience for the maintenance of object concepts in the same cohort of SD patients by using comprehensive assessments of different aspects of object knowledge across an experience-based, distributed semantic memory network. Here, we tested four SD patients and three Alzheimer's disease (AD) control patients using a range of tasks - including naming, gesture generation, and autobiographical knowledge - with personally familiar objects or perceptually similar or different object analogs. Our results showed dissociations between performance on naming relative to other assessments of object knowledge between SD and AD patients, though we did not observe a reliable familiar objects advantage. We discuss different factors that may account for these findings, as well as their implications for research on SD.

Hierarchical organization of scripts: converging evidence from FMRI and frontotemporal degeneration

The present study examined the organization of complex familiar activities, known as "scripts" (e.g., "going fishing"). We assessed whether events in a script are processed in a linear-sequential manner or clustered-hierarchical manner, and we evaluated the neural basis for this processing capacity. Converging evidence was obtained from functional neuroimaging in healthy young adults and from behavioral and structural magnetic resonance imaging (MRI) data in patients with focal neurodegenerative disease. In both studies, participants judged the order of consecutive event pairs taken from a script. Event pairs either were clustered together within a script or were from different clusters within the script. Controls judged events more accurately and quickly if taken from the same cluster within a script compared with different clusters, even though all event pairs were consecutive, consistent with the hierarchical organization of a script. Functional magnetic resonance imaging associated this with bilateral inferior frontal activation. Patients with progressive nonfluent aphasia or behavior-variant frontotemporal dementia did not distinguish between event pairs from the same cluster or from different clusters within a script. Structural MRI associated this deficit with significant frontal cortical atrophy. Our findings suggest that frontal cortex contributes to clustering events during script comprehension, underlining the role of frontal cortex in the hierarchical organization of a script.

Computerized analysis of speech and language to identify psycholinguistic correlates of frontotemporal lobar degeneration

OBJECTIVE

To evaluate the use of a semiautomated computerized system for measuring speech and language characteristics in patients with frontotemporal lobar degeneration (FTLD).

BACKGROUND

FTLD is a heterogeneous disorder comprising at least 3 variants. Computerized assessment of spontaneous verbal descriptions by patients with FTLD offers a detailed and reproducible view of the underlying cognitive deficits.

METHODS

Audiorecorded speech samples of 38 patients from 3 participating medical centers were elicited using the Cookie Theft stimulus. Each patient underwent a battery of neuropsychologic tests. The audio was analyzed by the computerized system to measure 15 speech and language variables. Analysis of variance was used to identify characteristics with significant differences in means between FTLD variants. Factor analysis was used to examine the implicit relations between subsets of the variables.

RESULTS

Semiautomated measurements of pause-to-word ratio and pronoun-to-noun ratio were able to discriminate between some of the FTLD variants. Principal component analysis of all 14 variables suggested 4 subjectively defined components (length, hesitancy, empty content, grammaticality) corresponding to the phenomenology of FTLD variants.

CONCLUSION

Semiautomated language and speech analysis is a promising novel approach to neuropsychologic assessment that offers a valuable contribution to the toolbox of researchers in dementia and other neurodegenerative disorders.

Speech errors in progressive non-fluent aphasia

The nature and frequency of speech production errors in neurodegenerative disease have not previously been precisely quantified. In the present study, 16 patients with a progressive form of non-fluent aphasia (PNFA) were asked to tell a story from a wordless children's picture book. Errors in production were classified as either phonemic, involving language-based deformations that nevertheless result in possible sequences of English speech segments; or phonetic, involving a motor planning deficit and resulting in non-English speech segments. The distribution of cortical atrophy as revealed by structural MRI scans was examined quantitatively in a subset of PNFA patients (N=7). The few errors made by healthy seniors were only phonemic in type. PNFA patients made more than four times as many errors as controls. This included both phonemic and phonetic errors, with a preponderance of errors (82%) classified as phonemic. The majority of phonemic errors were substitutions that shared most distinctive features with the target phoneme. The systematic nature of these substitutions is not consistent with a motor planning deficit. Cortical atrophy was found in prefrontal regions bilaterally and peri-Sylvian regions of the left hemisphere. We conclude that the speech errors produced by PNFA patients are mainly errors at the phonemic level of language processing and are not caused by a motor planning impairment.

Frontotemporal Lobar Degeneration: Characterizing Semantic Binding and Abstracted Meaning Abilities

Purpose: Frontotemporal lobar degeneration (FTLD) encompasses a group of neurodegenerative disorders characterized by gradual and progressive decline in behavior and/or language. Identifying the subtypes of FTLD can be challenging with traditional assessment tools. Growing empirical evidence suggests that language measures might be useful in differentiating FTLD subtypes.

Method: In this paper, we examined the performance of five individuals with FTLD (two with frontotemporal dementia, two with semantic dementia, and one with progressive nonfluent aphasia) and 10 cognitively normal older adults on measures of semantic binding (Semantic Object Retrieval Test and semantic problem solving) and abstracted meaning (generation of interpretive statement and proverb interpretation).

Results and Conclusion: A differential profile of impairment was observed in the three FTLD subtypes on these four measures. Further examination of these measures in larger groups will establish their clinical utility in differentiating the FTLD subtypes.

Sentence comprehension and voxel-based morphometry in progressive nonfluent aphasia, semantic dementia, and nonaphasic frontotemporal dementia

To investigate the basis for impaired sentence comprehension in patients with frontotemporal dementia (FTD) we assessed grammatical comprehension and verbal working memory in 88 patients with three distinct presentations: progressive nonfluent aphasia (PNFA), semantic dementia (SD), and nonaphasic patients with a disorder of social comportment and executive processing (SOC/EXEC). We related sentence comprehension and working memory performance to regional cortical volume in a subgroup of 29 patients with structural MRI scans using voxel-based morphometry. PNFA patients exhibited the greatest difficulty with sentence comprehension and were especially impaired with grammatically complex sentences, which correlated with atrophy in left inferior frontal cortex. Working memory performance in these same patients correlated with a proximal but distinct left inferior frontal region. SD patients' sentence comprehension scores correlated with left inferolateral temporal lobe damage, which we hypothesize and reflect impairments in lexical processing. We did not observe any consistent relationship between cortical atrophy and sentence comprehension impairment in SOC/EXEC patients, suggesting the deficits in this subgroup may be due to more variable declines in executive resources.

Syntactic and thematic components of sentence processing in progressive nonfluent aphasia and nonaphasic frontotemporal dementia

We used an online word-monitoring paradigm to examine sentence processing in healthy seniors and frontotemporal dementia patients with progressive nonfluent aphasia (PNFA) or a nonaphasic disorder of social and executive functioning (SOC/EXEC). Healthy seniors were sensitive to morphosyntactic, major grammatical subcategory, and selection restriction violations in a sentence. PNFA patients were insensitive to grammatical errors, but showed reasonable sensitivity to thematic matrix violations, consistent with a differential grammatical processing impairment. By contrast, SOC/EXEC patients showed partial sensitivity to grammatical errors but were insensitive to thematic violations. These findings support a dissociation between grammatical and thematic components of sentence processing. Specifically, they are consistent with a grammatical processing deficit in PNFA patients, and impairment in the formation of a coherent thematic matrix in SOC/EXEC patients.

Verb acquisition and representation in Alzheimer's disease

We examined the implicit acquisition and mental representation of a novel verb in patients with probable Alzheimer's disease (AD). Patients were exposed to the new verb in a naturalistic manner as part of a simple picture story. We probed grammatical, semantic and thematic matrix knowledge of the verb soon after presentation and again 1 week later. We found partial verb acquisition that was retained over 1 week. AD patients did not differ from controls in their acquisition and retention of a new verb's major grammatical subcategory, although they acquired little of its semantic properties and displayed minimal acquisition of the new word's thematic matrix. Moreover, AD patients appeared to maintain their acquired grammatical knowledge over 1 week. We discuss the implications of these findings from several perspectives, including the modularity of the language processing system, the relationship between episodic memory and semantic memory, and the role of the preserved implicit memory system in AD patients' partially successful lexical acquisition.