Grammatical comprehension deficits in non-fluent/agrammatic primary progressive aphasia

Non-pharmacological interventions for improving language and communication in people with primary progressive aphasia

BACKGROUND

Primary progressive aphasia (PPA) accounts for approximately 43% of frontotemporal dementias and is mainly characterised by a progressive impairment of speech and communication abilities. Three clinical variants have been identified: (a) non-fluent/agrammatic, (b) semantic, and (c) logopenic/phonological PPA variants. There is currently no curative treatment for PPA, and the disease progresses inexorably over time, with devastating effects on speech and communication ability, functional status, and quality of life. Several non-pharmacological interventions that may improve symptoms (e.g. different forms of language training and non-invasive brain stimulation) have been investigated in people with PPA.

OBJECTIVES

To assess the effects of non-pharmacological interventions for people with PPA on word retrieval (our primary outcome), global language functions, cognition, quality of life, and adverse events.

SEARCH METHODS

We searched the Cochrane Dementia and Cognitive Improvement Group's trial register, MEDLINE (Ovid SP), Embase (Ovid SP), four other databases and two other trial registers. The latest searches were run on 26 January 2024.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) evaluating the effects of non-pharmacological interventions in people with PPA.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

There were insufficient data available to conduct the network meta-analyses that we had originally planned (due to trial data being insufficiently reported or not reported at all, as well as the heterogeneous content of the included interventions). Therefore, we provide a descriptive summary of the included studies and results. We included 10 studies, with a total of 132 participants, evaluating non-pharmacological interventions. These were: transcranial direct current stimulation (tDCS) or repetitive transcranial magnetic stimulation (rTMS) as stand-alone treatments (used by two and one studies, respectively); tDCS combined with semantic and phonological word-retrieval training (five studies); tDCS combined with semantic word-retrieval training (one study); and tDCS combined with phonological word-retrieval training (one study). Results for our primary outcome of word retrieval were mixed. For the two studies that investigated the effects of tDCS as stand-alone treatment compared to placebo ("sham") tDCS, we rated the results as having very low-certainty evidence. One study found a significant beneficial effect on word retrieval after active tDCS; one study did not report any significant effects in favour of the active tDCS group. Five studies investigated tDCS administered to the dorsolateral prefrontal cortex, inferior frontal cortex, left frontotemporal region, or the temporoparietal cortex, combined with semantic and phonological word-retrieval training. The most consistent finding was enhancement of word-retrieval ability for trained items immediately after the intervention, when behavioural training was combined with active tDCS compared to behavioural training plus sham tDCS. We found mixed effects for untrained items and maintenance of treatment effects during follow-up assessments. We rated the certainty of the evidence as very low in all studies. One study investigated tDCS combined with semantic word-retrieval training. Training was provided across 15 sessions with a frequency of three to five sessions per week, depending on the personal preferences of the participants. tDCS targeted the left frontotemporal region. The study included three participants: two received 1 mA stimulation and one received 2 mA stimulation. The study showed mixed results. We rated it as very low-certainty evidence. One study investigated tDCS combined with phonological word-retrieval training. Training was again provided across 15 sessions over a period of three weeks. tDCS targeted the left inferior frontal gyrus. This study showed a significantly more pronounced improvement for trained and untrained words in favour of the group that had received active tDCS, but we rated the certainty of the evidence as very low. One study compared active rTMS applied to an individually determined target site to active rTMS applied to a control site (vertex) for effects on participants' word retrieval. This study demonstrated better word retrieval for active rTMS administered to individually determined target brain regions than in the control intervention, but we rated the results as having a very low certainty of evidence. Four studies assessed overall language ability, three studies assessed cognition, five studies assessed potential adverse effects of brain stimulation, and one study investigated quality of life.

AUTHORS' CONCLUSIONS

There is currently no high-certainty evidence to inform clinical decision-making regarding non-pharmacological treatment selection for people with PPA. Preliminary evidence suggests that the combination of active tDCS with specific language therapy may improve impaired word retrieval for specifically trained items beyond the effects of behavioural treatment alone. However, more research is needed, including high-quality RCTs with detailed descriptions of participants and methods, and consideration of outcomes such as quality of life, depressive symptoms, and overall cognitive functioning. Moreover, studies assessing optimal treatments (i.e. behavioural interventions, brain stimulation interventions, and their combinations) for individual patients and PPA subtypes are needed. We were not able to conduct the planned (network) meta-analyses due to missing data that could not be obtained from most of the authors, a general lack of RCTs in the field, and heterogeneous interventions in eligible trials. Journals should implement a mandatory data-sharing requirement to assure transparency and accessibility of data from clinical trials.

Neural basis of speech and grammar symptoms in non-fluent variant primary progressive aphasia spectrum

The non-fluent/agrammatic variant of primary progressive aphasia (nfvPPA) is a neurodegenerative syndrome primarily defined by the presence of apraxia of speech (AoS) and/or expressive agrammatism. In addition, many patients exhibit dysarthria and/or receptive agrammatism. This leads to substantial phenotypic variation within the speech-language domain across individuals and time, in terms of both the specific combination of symptoms as well as their severity. How to resolve such phenotypic heterogeneity in nfvPPA is a matter of debate. 'Splitting' views propose separate clinical entities: 'primary progressive apraxia of speech' when AoS occurs in the absence of expressive agrammatism, 'progressive agrammatic aphasia' (PAA) in the opposite case, and 'AOS + PAA' when mixed motor speech and language symptoms are clearly present. While therapeutic interventions typically vary depending on the predominant symptom (e.g. AoS versus expressive agrammatism), the existence of behavioural, anatomical and pathological overlap across these phenotypes argues against drawing such clear-cut boundaries. In the current study, we contribute to this debate by mapping behaviour to brain in a large, prospective cohort of well characterized patients with nfvPPA (n = 104). We sought to advance scientific understanding of nfvPPA and the neural basis of speech-language by uncovering where in the brain the degree of MRI-based atrophy is associated with inter-patient variability in the presence and severity of AoS, dysarthria, expressive agrammatism or receptive agrammatism. Our cross-sectional examination of brain-behaviour relationships revealed three main observations. First, we found that the neural correlates of AoS and expressive agrammatism in nfvPPA lie side by side in the left posterior inferior frontal lobe, explaining their behavioural dissociation/association in previous reports. Second, we identified a 'left-right' and 'ventral-dorsal' neuroanatomical distinction between AoS versus dysarthria, highlighting (i) that dysarthria, but not AoS, is significantly influenced by tissue loss in right-hemisphere motor-speech regions; and (ii) that, within the left hemisphere, dysarthria and AoS map onto dorsally versus ventrally located motor-speech regions, respectively. Third, we confirmed that, within the large-scale grammar network, left frontal tissue loss is preferentially involved in expressive agrammatism and left temporal tissue loss in receptive agrammatism. Our findings thus contribute to define the function and location of the epicentres within the large-scale neural networks vulnerable to neurodegenerative changes in nfvPPA. We propose that nfvPPA be redefined as an umbrella term subsuming a spectrum of speech and/or language phenotypes that are closely linked by the underlying neuroanatomy and neuropathology.

The ScreeLing: Detecting Semantic, Phonological, and Syntactic Deficits in the Clinical Subtypes of Frontotemporal and Alzheimer's Dementia

The ScreeLing is a screening instrument developed to assess post-stroke aphasia, via the linguistic levels Syntax, Phonology, and Semantics. It could also be a useful test for the clinical subtypes of frontotemporal dementia (FTD) and Alzheimer's dementia (AD), as specific and often selective disorders are expected. Its ability to differentiate between the clinical subtypes of FTD and AD is, however, still unknown. We investigated differences in ScreeLing total and subscores, linguistic-level disorders' relationship with disease severity, and classification abilities, in patients with behavioral variant FTD (bvFTD; n = 46), patients with primary progressive aphasia (PPA; n = 105) (semantic variant primary progressive aphasia [svPPA], non-fluent variant primary progressive aphasia [nfvPPA], and logopenic variant primary progressive aphasia [lvPPA], AD [n = 20] and controls [n = 35]). We examined group differences in ScreeLing total and subscores, and one-, two- or three-level linguistic disorders using one-way analyses of covariance (ANCOVAs) or Quade's rank ANCOVA. We used frequency analyses to obtain the occurrence of the linguistic-level disorders. We determined sensitivity and specificity by the area under the curve by receiver-operating characteristics analyses to investigate classification abilities. The total score was lower in patients (bvFTD: 63.8 ± 8.5, svPPA: 58.8 ± 11.3, nfvPPA: 63.5 ± 8.4, lvPPA: 61.7 ± 6.6, AD: 63.8 ± 5.5) than controls (71.3 ± 1.0) (p < .001). Syntax subscores were lower in svPPA (19.4 ± 4.6; p < .001) and lvPPA (20.3 ± 3.2; p = .002) than controls (23.8 ± 0.4). Phonology subscores were lower in lvPPA (19.8 ± 2.6) than bvFTD (21.7 ± 2.8) (p = .010). Semantics subscores were lowest in svPPA (17.8 ± 5.0; p < .002). A selective phonological disorder was most prevalent in lvPPA (34.9%). The higher the disease severity, the more linguistic-level disorders. The optimal cutoff for the total score was 70, and 23 for all three subscores. Good classification abilities were found for the Semantics (svPPA vs. bvFTD), Phonology (lvPPA vs. svPPA), and Syntax (nfvPPA vs. lvPPA) subscores. This easy to administer test gives information about language processing with the potential to improve differential diagnosis in memory clinics and in the future potentially also clinical trial planning.

Sentence Comprehension in Primary Progressive Aphasia: A Study of the Application of the Brazilian Version of the Test for the Reception of Grammar (TROG2-Br)

Sentence-comprehension deficits have been described in patients with primary progressive aphasia (PPA). However, most instruments to address this domain in more detail and in a clinical context have not been adapted and translated into several languages, posing limitations to clinical practice and cross-language research.

Objectives

The study aimed to (1) test the applicability of the Brazilian version of the Test for Reception of Grammar (TROG2-Br) to detect morphosyntactic deficits in patients with PPA; (2) investigate the association between performance in the test and sociodemographic and clinical variables (age, years of formal education, and disease duration); (3) characterize the performance of individuals presenting with the three more common variants of PPA (non-fluent, semantic, and logopenic) and mixed PPA (PPA-Mx) and analyze whether TROG-2 may assist in the distinction of these clinical profiles.

Methods

A total of 74 cognitively healthy participants and 34 individuals diagnosed with PPA were assessed with TROG2-Br. Overall scores (correct items, passed blocks), types, and categories of errors were analyzed.

Results

In controls, block scores were significantly correlated with years of formal education (Spearman's r = 0.33, p = 004) but not with age. In PPA, age, education, and disease duration were not significantly associated with performance in the test. Controls presented a significantly higher performance on TROG2-Br compared to PPA individuals and their errors pattern pointed to mild general cognitive processing difficulties (attention, working memory). PPA error types pointed to processing and morphosyntactic deficits in nonfluent or agrammatic PPA, (PPA-NF/A), logopenic PPA (PPA-L), and PPA-Mx. The semantic PPA (PPA-S) subgroup was qualitatively more similar to controls (processing difficulties and lower percentage of morphosyntactic errors). TROG2-Br presented good internal consistency and concurrent validity.

Discussion

Our results corroborate findings with TROG-2 in other populations. The performance of typical older adults with heterogeneous levels of education is discussed along with recommendations for clinical use of the test and future directions of research.

A 'Mini Linguistic State Examination' to classify primary progressive aphasia

There are few available methods for qualitatively evaluating patients with primary progressive aphasia. Commonly adopted approaches are time-consuming, of limited accuracy or designed to assess different patient populations. This paper introduces a new clinical test-the Mini Linguistic State Examination-which was designed uniquely to enable a clinician to assess and subclassify both classical and mixed presentations of primary progressive aphasia. The adoption of a novel assessment method (error classification) greatly amplifies the clinical information that can be derived from a set of standard linguistic tasks and allows a five-dimensional profile to be defined. Fifty-four patients and 30 matched controls were recruited. Five domains of language competence (motor speech, phonology, semantics, syntax and working memory) were assessed using a sequence of 11 distinct linguistic assays. A random forest classification was used to assess the diagnostic accuracy for predicting primary progressive aphasia subtypes and create a decision tree as a guide to clinical classification. The random forest prediction model was 96% accurate overall (92% for the logopenic variant, 93% for the semantic variant and 98% for the non-fluent variant). The derived decision tree produced a correct classification of 91% of participants whose data were not included in the training set. The Mini Linguistic State Examination is a new cognitive test incorporating a novel and powerful, yet straightforward, approach to scoring. Rigorous assessment of its diagnostic accuracy confirmed excellent matching of primary progressive aphasia syndromes to clinical gold standard diagnoses. Adoption of the Mini Linguistic State Examination by clinicians will have a decisive impact on the consistency and uniformity with which patients can be described clinically. It will also facilitate screening for cohort-based research, including future therapeutic trials, and is suitable for describing, quantifying and monitoring language deficits in other brain disorders.

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.

The Impact of Primary Progressive Aphasia on Picture Naming and General Language Ability

BACKGROUND

Primary progressive aphasia (PPA) is a clinical syndrome that is characterized by progressive deterioration of language while other cognitive domains remain relatively intact. The extent to which print exposure and cortical volume atrophy jointly influence picture naming and general language ability in individuals with PPA remains underexplored.

OBJECTIVE

To investigate the language performance of individuals with the nonfluent variant of primary progressive aphasia (nfvPPA) and to explore the impact of print exposure and cortical volume atrophy on their language ability.

METHOD

We compared 14 Greek individuals with nfvPPA and similar age, education, disease duration, and cognitive ability with age-, gender- and education-matched Greek controls on picture naming and on language tasks of the Boston Diagnostic Aphasia Examination-Short Form, including oral word reading, word and sentence repetition, complex ideational material, and reading comprehension. The effects of print exposure and left-hemisphere cortical volume on the individuals' language performance were estimated through stepwise regression models.

RESULTS

The language performance of the individuals with nfvPPA was affected by print exposure and cortical volume atrophy. Picture naming and word reading were affected by print exposure. The highest contributions of cortical volume atrophy were found for the repetition, complex ideational material, and reading comprehension tasks.

CONCLUSION

Print exposure and cortical volume atrophy may help explain variability in the language performance of nfvPPA individuals with similar age, education, disease duration, and cognitive ability.

More Than Words: Extra-Sylvian Neuroanatomic Networks Support Indirect Speech Act Comprehension and Discourse in Behavioral Variant Frontotemporal Dementia

Indirect speech acts—responding “I forgot to wear my watch today” to someone who asked for the time—are ubiquitous in daily conversation, but are understudied in current neurobiological models of language. To comprehend an indirect speech act like this one, listeners must not only decode the lexical-semantic content of the utterance, but also make a pragmatic, bridging inference. This inference allows listeners to derive the speaker’s true, intended meaning—in the above dialog, for example, that the speaker cannot provide the time. In the present work, we address this major gap by asking non-aphasic patients with behavioral variant frontotemporal dementia (bvFTD, n = 21) and brain-damaged controls with amnestic mild cognitive impairment (MCI, n = 17) to judge simple question-answer dialogs of the form: “Do you want some cake for dessert?” “I’m on a very strict diet right now,” and relate the results to structural and diffusion MRI. Accuracy and reaction time results demonstrate that subjects with bvFTD, but not MCI, are selectively impaired in indirect relative to direct speech act comprehension, due in part to their social and executive limitations, and performance is related to caregivers’ judgment of communication efficacy. MRI imaging associates the observed impairment in bvFTD to cortical thinning not only in traditional language-associated regions, but also in fronto-parietal regions implicated in social and executive cerebral networks. Finally, diffusion tensor imaging analyses implicate white matter tracts in both dorsal and ventral projection streams, including superior longitudinal fasciculus, frontal aslant, and uncinate fasciculus. These results have strong implications for updated neurobiological models of language, and emphasize a core, language-mediated social disorder in patients with bvFTD.

Thematic Integration Impairments in Primary Progressive Aphasia: Evidence From Eye-Tracking

Primary progressive aphasia (PPA) is a degenerative disease affecting language while leaving other cognitive facilities relatively unscathed. The agrammatic subtype of PPA (PPA-G) is characterized by agrammatic language production with impaired comprehension of noncanonical filler-gap syntactic structures, such as object-relatives [e.g., The sandwich that the girl ate (gap) was tasty], in which the filler (the sandwich) is displaced from the object position within the relative clause to a position preceding both the verb and the agent (the girl) and is replaced by a gap linked with the filler. One hypothesis suggests that the observed deficits of these structures reflect impaired thematic integration, including impaired prediction of the thematic role of the filler and impaired thematic integration at the gap, but spared structure building (i.e., creation of the gap). In the current study, we examined the on-line comprehension of object-relative and subject-relative clauses in healthy controls and individuals with agrammatic and logopenic PPA using eye-tracking. Eye-movement patterns in canonical subject-relative clause structures were essentially spared in both PPA groups. In contrast, eye-movement patterns in noncanonical object-relative clauses revealed delayed thematic prediction in both agrammatic and logopenic PPA, on-time structure building (i.e., gap-filling) in both groups, and abnormal thematic integration in agrammatic, but not logopenic, PPA. We argue that these results are consistent with the hypothesis that agrammatic comprehension deficits reflect impaired thematic integration.

Primary Progressive Aphasia and Stroke Aphasia

PURPOSE OF REVIEW

This article summarizes the clinical and anatomic features of the three named variants of primary progressive aphasia (PPA): semantic variant PPA, nonfluent/agrammatic variant PPA, and logopenic variant PPA. Three stroke aphasia syndromes that resemble the PPA variants (Broca aphasia, Wernicke aphasia, and conduction aphasia) are also presented.

RECENT FINDINGS

Semantic variant PPA and Wernicke aphasia are characterized by fluent speech with naming and comprehension difficulty; these syndromes are associated with disease in different portions of the left temporal lobe. Patients with nonfluent/agrammatic variant PPA or Broca aphasia have nonfluent speech with grammatical difficulty; these syndromes are associated with disease centered in the left inferior frontal lobe. Patients with logopenic variant PPA or conduction aphasia have difficulty with repetition and word finding in conversational speech; these syndromes are associated with disease in the left inferior parietal lobe. While PPA and stroke aphasias resemble one another, this article also presents their distinguishing features.

SUMMARY

Primary progressive and stroke aphasia syndromes interrupt the left perisylvian language network, resulting in identifiable aphasic syndromes.

A longitudinal study of speech production in primary progressive aphasia and behavioral variant frontotemporal dementia

We examined longitudinal change in language expression during a semi-structured speech sample in 48 patients with primary progressive aphasia (PPA) or behavioral variant frontotemporal dementia (bvFTD) and related this to longitudinal neuroimaging of cortical thickness available in 25 of these patients. All patient groups declined significantly on measures of both speech fluency and grammar, although patients with nonfluent/agrammatic PPA (naPPA) declined to a greater extent than patients with the semantic variant, the logopenic variant, and bvFTD. These patient groups also declined on several neuropsychological measures, but there was no correlation between decline in speech expression and decline in neuropsychological performance. Longitudinal decline in grammaticality, assessed by the number of well-formed sentences produced, was associated with longitudinal progression of gray matter atrophy in left frontal operculum/insula and bilateral temporal cortex.

Correlates of anomia in non-semantic variants of primary progressive aphasia converge over time

To track neural correlates of naming performance with disease progression, we estimated key areas affected in nonfluent/agrammatic (nfvPPA) and logopenic (lvPPA) primary progressive aphasia variants over time and changes in naming correlates over time. Twenty-nine non-semantic PPA participants (17 nfvPPA and 12 lvPPA) were selected based upon current diagnostic criteria and PiB-PET status and conducted a confrontation-naming task and a structural MRI. Linear mixed-effect models implemented in FreeSurfer were used for tracking cortical thickness and epicenters of atrophy over time. Using averaged cortical thickness of epicenters and naming performance as variables of interest, two sets of multivariate analyses were conducted to compare atrophy progression and naming correlates across groups. While all PPA participants demonstrated naming deterioration and progressive cortical thinning in the left temporal lobe and the left inferior frontal gyrus, the lvPPA cohort showed greater naming deterioration and thinning in the left posterior inferior parietal cortex over time than it did the nfvPPA cohort. The multivariate analyses confirmed a widespread cortical thinning in lvPPA over time, but a more rapid thinning in the right superior frontal gyrus of nfvPPA participants. Impaired naming correlated with common cortical regions in both groups. These regions included the left anterior superior temporal gyrus and the posterior middle temporal gyrus, which was primarily affected in lvPPA. Non-semantic PPA variants initially present with separate epicenters of atrophy and different spatial-temporal patterns of neurodegeneration over time, but the common involvement in key cortical regions of the left temporal lobe accounts for naming deterioration in both groups.

Direct electrical stimulation of the left frontal aslant tract disrupts sentence planning without affecting articulation

Sentence production involves mapping from deep structures that specify meaning and thematic roles to surface structures that specify the order and sequencing of production ready elements. We propose that the frontal aslant tract is a key pathway for sequencing complex actions with deep hierarchical structure. In the domain of language, and primarily with respect to the left FAT, we refer to this as the 'Syntagmatic Constraints On Positional Elements' (SCOPE) hypothesis. One prediction made by the SCOPE hypothesis is that disruption of the frontal aslant tract should disrupt sentence production at grammatical phrase boundaries, with no disruption of articulatory processes.  We test this prediction in a patient undergoing direct electrical stimulation mapping of the frontal aslant tract during an awake craniotomy to remove a left frontal brain tumor. We found that stimulation of the left FAT prolonged inter-word durations at the start of grammatical phrases, while inter-word durations internal to noun phrases were unaffected, and there was no effect on intra-word articulatory duration. These results provide initial support for the SCOPE hypothesis, and motivate novel directions for future research to explore the functions of this recently discovered component of the language system.

Asymmetry of post-mortem neuropathology in behavioural-variant frontotemporal dementia

Antemortem behavioural and anatomic abnormalities have largely been associated with right hemisphere disease in behavioural-variant frontotemporal dementia, but post-mortem neuropathological examination of bilateral hemispheres remains to be defined. Here we measured the severity of post-mortem pathology in both grey and white matter using a validated digital image analysis method in four cortical regions sampled from each hemisphere in 26 patients with behavioural-variant frontotemporal dementia, including those with frontotemporal degeneration (i.e. tau = 9, TDP-43 = 14, or FUS = 1 proteinopathy) or Alzheimer's pathology (n = 2). We calculated an asymmetry index based on the difference in measured pathology from each left-right sample pair. Analysis of the absolute value of the asymmetry index (i.e. degree of asymmetry independent of direction) revealed asymmetric pathology for both grey and white matter in all four regions sampled in frontototemporal degeneration patients with tau or TDP-43 pathology (P ≤ 0.01). Direct interhemispheric comparisons of regional pathology measurements within-subjects in the combined tauopathy and TDP-43 proteinopathy group found higher pathology in the right orbitofrontal grey matter compared to the left (P < 0.01) and increased pathology in ventrolateral temporal lobe grey matter of the left hemisphere compared to the right (P < 0.02). Preliminary group-wise comparisons between tauopathy and TDP-43 proteinopathy groups found differences in patterns of interhemispheric burden of grey and white matter regional pathology, with greater relative white matter pathology in tauopathies. To test the association of pathology measurement with ante-mortem observations, we performed exploratory analyses in the subset of patients with imaging data (n = 15) and found a direct association for increasing pathologic burden with decreasing cortical thickness in frontotemporal regions on ante-mortem imaging in tauopathy (P = 0.001) and a trend for TDP-43 proteinopathy (P = 0.06). Exploratory clinicopathological correlations demonstrated an association of socially-inappropriate behaviours with asymmetric right orbitofrontal grey matter pathology, and reduced semantically-guided category naming fluency was associated asymmetric white matter pathology in the left ventrolateral temporal region. We conclude that pathologic disease burden is distributed asymmetrically in behavioural-variant frontotemporal dementia, although not universally in the right hemisphere, and this asymmetry contributes to the clinical heterogeneity of the disorder. The basis for this asymmetric profile is enigmatic but may reflect distinct species or strains of tau and TDP-43 pathologies with propensities to spread by distinct cell- and region-specific mechanisms. Patterns of region-specific pathology in the right hemisphere as well as the left hemisphere may play a role in antemortem clinical observations, and these observations may contribute to antemortem identification of molecular pathology in frontotemporal degeneration.

Validated automatic speech biomarkers in primary progressive aphasia

Objective

To automatically extract and quantify specific disease biomarkers of prosody from the acoustic properties of speech in patients with primary progressive aphasia.

Methods

We analyzed speech samples from 59 progressive aphasic patients (non‐fluent/agrammatic = 15, semantic = 21, logopenic = 23; ages 50–85 years) and 31 matched healthy controls (ages 54–89 years). Using a novel, automated speech analysis protocol, we extracted acoustic measurements of prosody, including fundamental frequency and speech and silent pause durations, and compared these between groups. We then examined their relationships with clinical tests, gray matter atrophy, and cerebrospinal fluid analytes.

Results

We found a narrowed range of fundamental frequency in patients with non‐fluent/agrammatic variant aphasia (mean 3.86 ± 1.15 semitones) compared with healthy controls (6.06 ± 1.95 semitones; P < 0.001) and patients with semantic variant aphasia (6.12 ± 1.77 semitones; P = 0.001). Mean pause rate was significantly increased in the non‐fluent/agrammatic group (mean 61.4 ± 20.8 pauses per minute) and the logopenic group (58.7 ± 16.4 pauses per minute) compared to controls. In an exploratory analysis, narrowed fundamental frequency range was associated with atrophy in the left inferior frontal cortex. Cerebrospinal level of phosphorylated tau was associated with an acoustic classifier combining fundamental frequency range and pause rate (r = 0.58, P = 0.007). Receiver operating characteristic analysis with this combined classifier distinguished non‐fluent/agrammatic speakers from healthy controls (AUC = 0.94) and from semantic variant patients (AUC = 0.86).

Interpretation

Restricted fundamental frequency range and increased pause rate are characteristic markers of speech in non‐fluent/agrammatic primary progressive aphasia. These can be extracted with automated speech analysis and are associated with left inferior frontal atrophy and cerebrospinal phosphorylated tau level.

Longitudinal Changes in Semantic Concreteness in Semantic Variant Primary Progressive Aphasia (svPPA)

This study examines longitudinal changes in the concreteness of nouns produced by human patients with semantic variant primary progressive aphasia (svPPA). Cross-sectional studies show that patients with svPPA demonstrate severe loss of concrete noun knowledge linked to atrophy of the left ventral temporal lobe. It is unknown how disease spread and duration affect the magnitude of the concreteness impairment in svPPA. We evaluate longitudinal spoken production of concrete nouns in svPPA, and relate this to changes in longitudinal MRI measures of gray matter (GM). Noun concreteness in svPPA is compared to that of behavioral variant frontotemporal dementia (bvFTD) patients, who typically demonstrate highly concrete speech. We elicited naturalistic speech samples at two time points (time 1 and time 2) in patients with svPPA (n = 11) and bvFTD (n = 15) through descriptions of the Cookie Theft picture and evaluated each spoken noun for concreteness. Compared to bvFTD patients whose noun production remained highly concrete throughout the testing period, mixed-effects models revealed that noun concreteness significantly decreased as disease progressed in svPPA. We also measured longitudinal changes to GM in a subset of svPPA patients (n = 7), who showed significant decline in the left and right temporal and frontal regions. Regression analyses revealed that longitudinal GM atrophy in the right fusiform and parahippocampal gyri and the left superior temporal gyrus was related to decreasing noun concreteness. These results suggest that progressive atrophy of the ventral temporal lobe in svPPA contributes to declining concrete noun production over time.

Evidence of semantic processing impairments in behavioural variant frontotemporal dementia and Parkinson's disease

PURPOSE OF REVIEW

Category-specific impairments caused by brain damage can provide important insights into how semantic concepts are organized in the brain. Recent research has demonstrated that disease to sensory and motor cortices can impair perceptual feature knowledge important to the representation of semantic concepts. This evidence supports the grounded cognition theory of semantics, the view that lexical knowledge is partially grounded in perceptual experience and that sensory and motor regions support semantic representations. Less well understood, however, is how heteromodal semantic hubs work to integrate and process semantic information.

RECENT FINDINGS

Although the majority of semantic research to date has focused on how sensory cortical areas are important for the representation of semantic features, new research explores how semantic memory is affected by neurodegeneration in regions important for semantic processing. Here, we review studies that demonstrate impairments to abstract noun knowledge in behavioural variant frontotemporal degeneration (bvFTD) and to action verb knowledge in Parkinson's disease, and discuss how these deficits relate to disease of the semantic selection network.

SUMMARY

Findings demonstrate that semantic selection processes are supported by the left inferior frontal gyrus (LIFG) and basal ganglia, and that disease to these regions in bvFTD and Parkinson's disease can lead to categorical impairments for abstract nouns and action verbs, respectively.

Linguistic Aspects of Primary Progressive Aphasia

Primary progressive aphasia (PPA) refers to a disorder of declining language associated with neurodegenerative diseases such as frontotemporal degeneration and Alzheimer disease. Variants of PPA are important to recognize from a medical perspective because these syndromes are clinical markers suggesting specific underlying pathology. In this review, I discuss linguistic aspects of PPA syndromes that may prove informative for parsing our language mechanism and identifying the neural representation of fundamental elements of language. I focus on the representation of word meaning in a discussion of semantic variant PPA, grammatical comprehension and expression in a discussion of nonfluent/agrammatic variant PPA, the supporting role of short-term memory in a discussion of logopenic variant PPA, and components of language associated with discourse in a discussion of behavioral variant frontotemporal dementia. PPA provides a novel perspective that uniquely addresses facets of language and its disorders while complementing traditional aphasia syndromes that follow stroke.

Neuroimaging in Dementia

Although the diagnosis of dementia still is primarily based on clinical criteria, neuroimaging is playing an increasingly important role. This is in large part due to advances in techniques that can assist with discriminating between different syndromes. Magnetic resonance imaging remains at the core of differential diagnosis, with specific patterns of cortical and subcortical changes having diagnostic significance. Recent developments in molecular PET imaging techniques have opened the door for not only antemortem but early, even preclinical, diagnosis of underlying pathology. This is vital, as treatment trials are underway for pharmacological agents with specific molecular targets, and numerous failed trials suggest that earlier treatment is needed. This article provides an overview of classic neuroimaging findings as well as new and cutting-edge research techniques that assist with clinical diagnosis of a range of dementia syndromes, with an emphasis on studies using pathologically proven cases.

Automatic measurement of prosody in behavioral variant FTD

OBJECTIVE

To help understand speech changes in behavioral variant frontotemporal dementia (bvFTD), we developed and implemented automatic methods of speech analysis for quantification of prosody, and evaluated clinical and anatomical correlations.

METHODS

We analyzed semi-structured, digitized speech samples from 32 patients with bvFTD (21 male, mean age 63 ± 8.5, mean disease duration 4 ± 3.1 years) and 17 matched healthy controls (HC). We automatically extracted fundamental frequency (f0, the physical property of sound most closely correlating with perceived pitch) and computed pitch range on a logarithmic scale (semitone) that controls for individual and sex differences. We correlated f0 range with neuropsychiatric tests, and related f0 range to gray matter (GM) atrophy using 3T T1 MRI.

RESULTS

We found significantly reduced f0 range in patients with bvFTD (mean 4.3 ± 1.8 ST) compared to HC (5.8 ± 2.1 ST; p = 0.03). Regression related reduced f0 range in bvFTD to GM atrophy in bilateral inferior and dorsomedial frontal as well as left anterior cingulate and anterior insular regions.

CONCLUSIONS

Reduced f0 range reflects impaired prosody in bvFTD. This is associated with neuroanatomic networks implicated in language production and social disorders centered in the frontal lobe. These findings support the feasibility of automated speech analysis in frontotemporal dementia and other disorders.

Longitudinal decline in speech production in Parkinson's disease spectrum disorders

We examined narrative speech production longitudinally in non-demented (n=15) and mildly demented (n=8) patients with Parkinson's disease spectrum disorder (PDSD), and we related increasing impairment to structural brain changes in specific language and motor regions. Patients provided semi-structured speech samples, describing a standardized picture at two time points (mean±SD interval=38±24months). The recorded speech samples were analyzed for fluency, grammar, and informativeness. PDSD patients with dementia exhibited significant decline in their speech, unrelated to changes in overall cognitive or motor functioning. Regression analysis in a subset of patients with MRI scans (n=11) revealed that impaired language performance at Time 2 was associated with reduced gray matter (GM) volume at Time 1 in regions of interest important for language functioning but not with reduced GM volume in motor brain areas. These results dissociate language and motor systems and highlight the importance of non-motor brain regions for declining language in PDSD.

Baseline Performance Predicts tDCS-Mediated Improvements in Language Symptoms in Primary Progressive Aphasia

Primary Progressive Aphasia (PPA) is a neurodegenerative condition characterized by insidious irreversible loss of language abilities. Prior studies suggest that transcranial direct current stimulation (tDCS) directed toward language areas of the brain may help to ameliorate symptoms of PPA. In the present sham-controlled study, we examined whether tDCS could be used to enhance language abilities (e.g., picture naming) in individuals with PPA variants primarily characterized by difficulties with speech production (non-fluent and logopenic). Participants were recruited from the Penn Frontotemporal Dementia Center to receive 10 days of both real and sham tDCS (counter-balanced, full-crossover design; participants were naïve to stimulation condition). A battery of language tests was administered at baseline, immediately post-tDCS (real and sham), and 6 weeks and 12 weeks following stimulation. When we accounted for individuals' baseline performance, our analyses demonstrated a stratification of tDCS effects. Individuals who performed worse at baseline showed tDCS-related improvements in global language performance, grammatical comprehension and semantic processing. Individuals who performed better at baseline showed a slight tDCS-related benefit on our speech repetition metric. Real tDCS may improve language performance in some individuals with PPA. Severity of deficits at baseline may be an important factor in predicting which patients will respond positively to language-targeted tDCS therapies. Clinicaltrials.gov ID: NCT02928848.

Improving language mapping in clinical fMRI through assessment of grammar

Introduction

Brain surgery in the language dominant hemisphere remains challenging due to unintended post-surgical language deficits, despite using pre-surgical functional magnetic resonance (fMRI) and intraoperative cortical stimulation. Moreover, patients are often recommended not to undergo surgery if the accompanying risk to language appears to be too high. While standard fMRI language mapping protocols may have relatively good predictive value at the group level, they remain sub-optimal on an individual level. The standard tests used typically assess lexico-semantic aspects of language, and they do not accurately reflect the complexity of language either in comprehension or production at the sentence level. Among patients who had left hemisphere language dominance we assessed which tests are best at activating language areas in the brain.

Method

We compared grammar tests (items testing word order in actives and passives, wh-subject and object questions, relativized subject and object clauses and past tense marking) with standard tests (object naming, auditory and visual responsive naming), using pre-operative fMRI. Twenty-five surgical candidates (13 females) participated in this study. Sixteen patients presented with a brain tumor, and nine with epilepsy. All participants underwent two pre-operative fMRI protocols: one including CYCLE-N grammar tests (items testing word order in actives and passives, wh-subject and object questions, relativized subject and object clauses and past tense marking); and a second one with standard fMRI tests (object naming, auditory and visual responsive naming). fMRI activations during performance in both protocols were compared at the group level, as well as in individual candidates.

Results

The grammar tests generated more volume of activation in the left hemisphere (left/right angular gyrus, right anterior/posterior superior temporal gyrus) and identified additional language regions not shown by the standard tests (e.g., left anterior/posterior supramarginal gyrus). The standard tests produced more activation in left BA 47. Ten participants had more robust activations in the left hemisphere in the grammar tests and two in the standard tests. The grammar tests also elicited substantial activations in the right hemisphere and thus turned out to be superior at identifying both right and left hemisphere contribution to language processing.

Conclusion

The grammar tests may be an important addition to the standard pre-operative fMRI testing.

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We added comprehensive grammar tests to standard presurgical fMRI of language.

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The grammar tests generated more volume of activation bilaterally.

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The tests identified additional language regions not shown by the standard tests.

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The grammar tests may be an important addition to standard pre-operative fMRI.

Non-invasive Brain Stimulation in the Treatment of Post-stroke and Neurodegenerative Aphasia: Parallels, Differences, and Lessons Learned

Numerous studies over the span of more than a decade have shown that non-invasive brain stimulation (NIBS) techniques, namely transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), can facilitate language recovery for patients who have suffered from aphasia due to stroke. While stroke is the most common etiology of aphasia, neurodegenerative causes of language impairment—collectively termed primary progressive aphasia (PPA)—are increasingly being recognized as important clinical phenotypes in dementia. Very limited data now suggest that (NIBS) may have some benefit in treating PPAs. However, before applying the same approaches to patients with PPA as have previously been pursued in patients with post-stroke aphasia, it will be important for investigators to consider key similarities and differences between these aphasia etiologies that is likely to inform successful approaches to stimulation. While both post-stroke aphasia and the PPAs have clear overlaps in their clinical phenomenology, the mechanisms of injury and theorized neuroplastic changes associated with the two etiologies are notably different. Importantly, theories of plasticity in post-stroke aphasia are largely predicated on the notion that regions of the brain that had previously been uninvolved in language processing may take on new compensatory roles. PPAs, however, are characterized by slow distributed degeneration of cellular units within the language system; compensatory recruitment of brain regions to subserve language is not currently understood to be an important aspect of the condition. This review will survey differences in the mechanisms of language representation between the two etiologies of aphasia and evaluate properties that may define and limit the success of different neuromodulation approaches for these two disorders.

The Mental Status Examination in Patients With Suspected Dementia

PURPOSE OF REVIEW

This article describes a comprehensive approach to the mental status examination and diagnostic workup of patients suspected of having an emerging neurodegenerative dementia. Key strategies for obtaining a history and bedside examination techniques are highlighted.

RECENT FINDINGS

Classic descriptions of behavioral neurology syndromes were largely based on clinicopathologic correlations of strategic lesions in stroke patients. While still very important, advances in neuroimaging have expanded our armamentarium of cognitive evaluations to include assessments of findings in nonstroke anatomic distributions of disease. These efforts support comprehensive assessments of large-scale cerebral networks in cognitive neurology.

SUMMARY

A thorough and focused mental status examination is essential for the evaluation of patients with cognitive symptoms. Selective use of laboratory testing and neuroimaging can aid in the diagnosis of dementia by excluding non-neurodegenerative etiologies. Neurodegenerative disease-specific tests are in development and will enhance diagnosis and efforts for disease-modifying therapy development.

Transcranial direct current stimulation for the treatment of primary progressive aphasia: An open-label pilot study

Primary progressive aphasia (PPA) is a neurodegenerative condition characterized by gradual deterioration of language function. We investigated whether two weeks of daily transcranial direct current stimulation (tDCS) treatment would improve language abilities in six people with a non-fluent form of PPA. tDCS was applied in an unblinded trial at an intensity of 1.5mA for 20min/day over 10days. At the time of stimulation, patients were engaged in narrating one of several children's wordless picture stories. A battery of neuropsychological assessments was administered four times: at baseline, immediately following the 2-week stimulation period, and then 6-weeks and 12-weeks following the end of stimulation. We observed improvement in linguistic performance in the domains of speech production and grammatical comprehension. Our encouraging results indicate that larger, sham-controlled studies of tDCS as a potential intervention for PPA are warranted.

Variable disruption of a syntactic processing network in primary progressive aphasia

Syntactic processing deficits are highly variable in individuals with primary progressive aphasia. Damage to left inferior frontal cortex has been associated with syntactic deficits in primary progressive aphasia in a number of structural and functional neuroimaging studies. However, a contrasting picture of a broader syntactic network has emerged from neuropsychological studies in other aphasic cohorts, and functional imaging studies in healthy controls. To reconcile these findings, we used functional magnetic resonance imaging to investigate the functional neuroanatomy of syntactic comprehension in 51 individuals with primary progressive aphasia, composed of all clinical variants and a range of degrees of syntactic processing impairment. We used trial-by-trial reaction time as a proxy for syntactic processing load, to determine which regions were modulated by syntactic processing in each patient, and how the set of regions recruited was related to whether syntactic processing was ultimately successful or unsuccessful. Relationships between functional abnormalities and patterns of cortical atrophy were also investigated. We found that the individual degree of syntactic comprehension impairment was predicted by left frontal atrophy, but also by functional disruption of a broader syntactic processing network, comprising left posterior frontal cortex, left posterior temporal cortex, and the left intraparietal sulcus and adjacent regions. These regions were modulated by syntactic processing in healthy controls and in patients with primary progressive aphasia with relatively spared syntax, but they were modulated to a lesser extent or not at all in primary progressive aphasia patients whose syntax was relatively impaired. Our findings suggest that syntactic comprehension deficits in primary progressive aphasia reflect not only structural and functional changes in left frontal cortex, but also disruption of a wider syntactic processing network.

Cognitive and anatomic double dissociation in the representation of concrete and abstract words in semantic variant and behavioral variant frontotemporal degeneration

We examine the anatomic basis for abstract and concrete lexical representations in semantic memory by assessing patients with focal neurodegenerative disease. Prior evidence from healthy adult studies suggests that there may be an anatomical dissociation between abstract and concrete representations: abstract words more strongly activate the left inferior frontal gyrus relative to concrete words, while concrete words more strongly activate left anterior-inferior temporal regions. However, this double dissociation has not been directly examined. We test this dissociation in two patient groups with focal cortical atrophy in each of these regions, the behavioral variant of Frontotemporal Degeneration (bvFTD) and the semantic variant of Primary Progressive Aphasia (svPPA). We administered an associativity judgment task for abstract and concrete words, where subjects select which of two words is best associated with a given target word. Both bvFTD and svPPA patients were significantly impaired in their overall performance compared to controls. While controls treated concrete and abstract words equally, we found a category-specific double dissociation in patients' judgments: bvFTD patients showed a concreteness effect (CE), with significantly worse performance for abstract compared to concrete words, while svPPA patients showed reversal of the CE, with significantly worse performance for concrete over abstract words. Regression analyses also revealed an anatomic double dissociation: The CE is associated with inferior frontal atrophy in bvFTD, while reversal of the CE is associated with left anterior-inferior temporal atrophy in svPPA. These results support a cognitive and anatomic model of semantic memory organization where abstract and concrete representations are supported by dissociable neuroanatomic substrates.

Processing ambiguity in a linguistic context: decision-making difficulties in non-aphasic patients with behavioral variant frontotemporal degeneration

Some extent of ambiguity is ubiquitous in everyday conversations. For example, words have multiple meaning and very common pronouns, like “he” and “she” (anaphoric pronouns), have little meaning on their own and refer to a noun that has been previously introduced in the discourse. Ambiguity triggers a decision process that is not a subroutine of language processing but rather a more general domain resource. Therefore non-aphasic patients with limited decision-making capability can encounter severe limitation in language processing due to extra linguistic limitations. In the present study, we test patients with behavioral variant frontotemporal degeneration (bvFTD), focusing on anaphora as a paradigmatic example of ambiguity resolution in the linguistic domain. bvFTD is characterized by gray matter (GM) atrophy in prefrontal cortex, but relative sparing of peri-Sylvian cortex. A group of patients with parietal disease due to corticobasal syndrome (CBS) was also tested here in order to investigate the specific role of prefrontal cortex in the task employed in the current study. Participants were presented with a pair of sentences in which the first sentence contained two nouns while the second contained a pronoun. In the experimental (ambiguous) condition, both nouns are plausible referents of the pronoun, thus requiring decision-making resources. The results revealed that bvFTD patients are significantly less accurate than healthy seniors in identifying the correct referent of a pronoun in the ambiguous condition, although CBS patients were as accurate as healthy seniors. Imaging analyses related bvFTD patients’ performance to GM atrophy in ventromedial prefrontal cortex (vmPFC). These results suggest that bvFTD patients have difficulties in decision processes that involve the resolution of an ambiguity.

Classification and clinicoradiologic features of primary progressive aphasia (PPA) and apraxia of speech

The consensus criteria for the diagnosis and classification of primary progressive aphasia (PPA) have served as an important tool in studying this group of disorders. However, a large proportion of patients remain unclassifiable whilst others simultaneously meet criteria for multiple subtypes. We prospectively evaluated a large cohort of patients with degenerative aphasia and/or apraxia of speech using multidisciplinary clinical assessments and multimodal imaging. Blinded diagnoses were made using operational definitions with important differences compared to the consensus criteria. Of the 130 included patients, 40 were diagnosed with progressive apraxia of speech (PAOS), 12 with progressive agrammatic aphasia, 9 with semantic dementia, 52 with logopenic progressive aphasia, and 4 with progressive fluent aphasia, while 13 were unclassified. The PAOS and progressive fluent aphasia groups were least impaired. Performance on repetition and sentence comprehension was especially poor in the logopenic group. The semantic and progressive fluent aphasia groups had prominent anomia, but only semantic subjects had loss of word meaning and object knowledge. Distinct patterns of grey matter loss and white matter changes were found in all groups compared to controls. PAOS subjects had bilateral frontal grey matter loss, including the premotor and supplementary motor areas, and bilateral frontal white matter involvement. The agrammatic group had more widespread, predominantly left sided grey matter loss and white matter abnormalities. Semantic subjects had bitemporal grey matter loss and white matter changes, including the uncinate and inferior occipitofrontal fasciculi, whereas progressive fluent subjects only had left sided temporal involvement. Logopenic subjects had diffuse and bilateral grey matter loss and diffusion tensor abnormalities, maximal in the posterior temporal region. A diagnosis of logopenic aphasia was strongly associated with being amyloid positive (46/52 positive). Our findings support consideration of an alternative way of identifying and categorizing subtypes of degenerative speech and language disorders.

White matter tracts of speech and language

Diffusion tensor imaging (DTI) has been used to investigate the white matter (WM) tracts underlying the perisylvian cortical regions known to be associated with language function. The arcuate fasciculus is composed of 3 segments (1 long and 2 short) whose separate functions correlate with traditional models of conductive and transcortical motor or sensory aphasia, respectively. DTI mapping of language fibers is useful in presurgical planning for patients with dominant hemisphere tumors, particularly when combined with functional magnetic resonance imaging. DTI has found damage to language networks in stroke patients and has the potential to influence poststroke rehabilitation and treatment. Assessment of the WM tracts involved in the default mode network has been found to correlate with mild cognitive impairment, potentially explaining language deficits in patients with apparently mild small vessel ischemic disease. Different patterns of involvement of language-related WM structures appear to correlate with different clinical subtypes of primary progressive aphasias.

Translation, cross-cultural adaptation and applicability of the Brazilian version of the Frontotemporal Dementia Rating Scale (FTD-FRS)

BACKGROUND

Staging scales for dementia have been devised for grading Alzheimer's disease (AD) but do not include the specific symptoms of frontotemporal lobar degeneration (FTLD).

OBJECTIVE

To translate and adapt the Frontotemporal Dementia Rating Scale (FTD-FRS) to Brazilian Portuguese.

METHODS

The cross-cultural adaptation process consisted of the following steps: translation, back-translation (prepared by independent translators), discussion with specialists, and development of a final version after minor adjustments. A pilot application was carried out with 12 patients diagnosed with bvFTD and 11 with AD, matched for disease severity (CDR=1.0). The evaluation protocol included: Addenbrooke's Cognitive Examination-Revised (ACE-R), Mini-Mental State Examination (MMSE), Executive Interview (EXIT-25), Neuropsychiatric Inventory (NPI), Frontotemporal Dementia Rating Scale (FTD-FRS) and Clinical Dementia Rating scale (CDR).

RESULTS

The Brazilian version of the FTD-FRS seemed appropriate for use in this country. Preliminary results revealed greater levels of disability in bvFTD than in AD patients (bvFTD: 25% mild, 50% moderate and 25% severe; AD: 36.36% mild, 63.64% moderate). It appears that the CDR underrates disease severity in bvFTD since a relevant proportion of patients rated as having mild dementia (CDR=1.0) in fact had moderate or severe levels of disability according to the FTD-FRS.

CONCLUSION

The Brazilian version of the FTD-FRS seems suitable to aid staging and determining disease progression.