Verbal adynamia in parkinsonian syndromes: behavioral correlates and neuroanatomical substrate

Psychometrics and diagnostics of the Italian version of the Alternate Verbal Fluency Battery (AVFB) in non-demented Parkinson's disease patients

BACKGROUND

Verbal fluency (VF) tasks are known as suitable for detecting cognitive impairment (CI) in Parkinson's disease (PD). This study thus aimed to evaluate the psychometrics and diagnostics of the Alternate Verbal Fluency Battery (AVFB) by Costa et al. (2014) in an Italian cohort of non-demented PD patients, as well as to derive disease-specific cut-offs for it.

METHODS

N = 192 non-demented PD patients were screened with the Montreal Cognitive Assessment (MoCA) and underwent the AVFB-which includes phonemic, semantic and alternate VF tests (PVF; SVF; AVF), as well as a Composite Shifting Index (CSI) reflecting the "cost" of shifting from a single- to a double-cued VF task. Construct validity and diagnostics were assessed for each AVFB measure against the MoCA. Internal reliability and factorial validity were also tested.

RESULTS

The MoCA proved to be strongly associated with PVF, SVF and AVF scores, whilst moderately with the CSI. The AVFB was internally consistent and underpinned by a single component; however, an improvement in both internal reliability and fit to its factorial structure was observed when dropping the CSI. Demographically adjusted scores on PVF, SVF and AVF tests were diagnostically sound in detecting MoCA-defined cognitive impairment, whilst this was not true for the CSI. Disease-specific cut-offs for PVF, SVF and AVF tests were derived.

DISCUSSION

In conclusion, PVF, SVF and AVF tests are reliable, valid and diagnostically sound instruments to detect cognitive impairment in non-demented PD patients and are therefore recommended for use in clinical practice and research.

Differential linguistic features of verbal fluency in behavioral variant frontotemporal dementia and primary progressive aphasia

Frontotemporal dementia (FTD) is an early-onset neurodegenerative disorder with a heterogeneous clinical presentation. Verbal fluency is regularly used as a sensitive measure of language ability, semantic memory, and executive functioning, but qualitative changes in verbal fluency in FTD are currently overlooked. This retrospective study examined qualitative, linguistic features of verbal fluency in 137 patients with behavioral variant (bv)FTD (n = 50), or primary progressive aphasia (PPA) [25 non-fluent variant (nfvPPA), 27 semantic variant (svPPA), and 34 logopenic variant (lvPPA)] and 25 control participants. Between-group differences in clustering, switching, lexical frequency (LF), age of acquisition (AoA), neighborhood density (ND), and word length (WL) were examined in the category and letter fluency with analysis of variance adjusted for age, sex, and the total number of words. Associations with other cognitive functions were explored with linear regression analysis. The results showed that the verbal fluency performance of patients with svPPA could be distinguished from controls and other patient groups by fewer and smaller clusters, more switches, higher LF, and lower AoA (all p < 0.05). Patients with lvPPA specifically produced words with higher ND than the other patient groups (p < 0.05). Patients with bvFTD produced longer words than the PPA groups (p < 0.05). Clustering, switching, LF, AoA, and ND-but not WL-were differentially predicted by measures of language, memory, and executive functioning (range standardized regression coefficient 0.25-0.41). In addition to the total number of words, qualitative linguistic features differ between subtypes of FTD. These features provide additional information on lexical processing and semantic memory that may aid the differential diagnosis of FTD.

Primary progressive aphasia: six questions in search of an answer

Here, we review recent progress in the diagnosis and management of primary progressive aphasia-the language-led dementias. We pose six key unanswered questions that challenge current assumptions and highlight the unresolved difficulties that surround these diseases. How many syndromes of primary progressive aphasia are there-and is syndromic diagnosis even useful? Are these truly 'language-led' dementias? How can we diagnose (and track) primary progressive aphasia better? Can brain pathology be predicted in these diseases? What is their core pathophysiology? In addition, how can primary progressive aphasia best be treated? We propose that pathophysiological mechanisms linking proteinopathies to phenotypes may help resolve the clinical complexity of primary progressive aphasia, and may suggest novel diagnostic tools and markers and guide the deployment of effective therapies.

Neurocognitive correlates of semantic memory navigation in Parkinson's disease

Cognitive studies on Parkinson's disease (PD) reveal abnormal semantic processing. Most research, however, fails to indicate which conceptual properties are most affected and capture patients' neurocognitive profiles. Here, we asked persons with PD, healthy controls, and individuals with behavioral variant frontotemporal dementia (bvFTD, as a disease control group) to read concepts (e.g., 'sun') and list their features (e.g., hot). Responses were analyzed in terms of ten word properties (including concreteness, imageability, and semantic variability), used for group-level comparisons, subject-level classification, and brain-behavior correlations. PD (but not bvFTD) patients produced more concrete and imageable words than controls, both patterns being associated with overall cognitive status. PD and bvFTD patients showed reduced semantic variability, an anomaly which predicted semantic inhibition outcomes. Word-property patterns robustly classified PD (but not bvFTD) patients and correlated with disease-specific hypoconnectivity along the sensorimotor and salience networks. Fine-grained semantic assessments, then, can reveal distinct neurocognitive signatures of PD.

The Discourse Profile in Corticobasal Syndrome: A Comprehensive Clinical and Biomarker Approach

The aim of this study was to characterize the oral discourse of CBS patients and to verify whether measures obtained during a semi-spontaneous speech production could differentiate CBS patients from controls. A second goal was to compare the performance of patients with CBS probably due to Alzheimer's disease (CBS-AD) pathology and CBS not related to AD (CBS-non-AD) in the same measures, based on the brain metabolic status (FDG-PET) and in the presence of amyloid deposition (amyloid-PET). Results showed that CBS patients were significantly different from controls in speech rate, lexical level, informativeness, and syntactic complexity. Discursive measures did not differentiate CBS-AD from CBS-non-AD. However, CBS-AD displayed more lexical-semantic impairments than controls, a profile that is frequently reported in patients with clinical AD and the logopenic variant of primary progressive aphasia (lvPPA). CBS-non-AD presented mainly with impairments related to motor speech disorders and syntactic complexity, as seen in the non-fluent variant of PPA.

When it is not primary progressive aphasia: A scoping review of spoken language impairment in other neurodegenerative dementias

BACKGROUND

Progressive difficulties with spoken language occur across the spectrum of degenerative dementia. When not a primary presenting and dominant symptom, language difficulties may be overlooked in favor of more prominent cognitive, behavior, or motor deficits. The aim of this scoping review is to examine the extent and nature of the research evidence describing (1) the spoken language impairments found in non-language led dementias, (2) their impact on everyday living, and (3) the reported language interventions.

METHODS

We searched PubMed, MEDLINE, OVID-EMBASE, PsycINFO, and SpeechBITE using terms related to spoken language for the following dementia types: Parkinson's disease dementia (PDD), dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), cortico-basal syndrome (CBS), behavior variant frontotemporal dementia (bvFTD), early-onset Alzheimer's disease (EOAD), posterior cortical atrophy (PCA), and motor neuron disease associated with FTD (MND+FTD). Risk of bias was assessed with the QualSyst tool.

RESULTS

Seventy-three eligible studies were included. A wide range of spoken language impairments were reported, involving both linguistic (e.g., syntactic processing) and other cognitive (e.g., sustained attention) underlying mechanisms. Although the severity of these deficits was scarcely reported, in some cases they manifested as non-fluent, dynamic, and global aphasias. No papers in the review described either the impact of these language impairments on everyday living or language therapies to treat them.

DISCUSSION

There is a need to understand better the level of disability produced by language impairment in people living with non-language-led dementias. Our findings suggest three calls for action: (1) research studies should assess the clinical relevance of any spoken language deficits examined, (2) both linguistic and cognitive underlying mechanisms should be fully described (to inform the design of effective language and behavioral interventions), and (3) trials of language therapy should be conducted in those groups of individuals where significant language impairment is proved.

Case Report: Barely Able to Speak, Can't Stop Echoing: Echolalic Dynamic Aphasia in Progressive Supranuclear Palsy

The diagnostic criteria for progressive supranuclear palsy (PSP) incorporate two speech-language disturbances (SLDs), non-fluent/agrammatic primary progressive aphasia and progressive apraxia of speech, but overlook the inclusion of other SLDs, including dynamic aphasia (DA). Thus, there is a need to reappraise the broad spectrum of SLDs in PSP to include other presenting phenotypes. Here we report findings from the study of two elderly patients with PSP presenting with DA and irrepressible echolalia. Both patients had markedly impoverished verbal production, but their performance in other tasks (repetition and naming) and auditory comprehension were preserved or only mildly impaired. Experimental tests of DA revealed impaired word and sentence generation in response to verbal and non-verbal stimuli. Additional language and cognitive testing revealed different types of echolalia (mitigated, automatic, and echoing approval) as well as impaired inhibitory control and social cognition (mentalizing). Both patients had negative neuropsychiatric alterations (i.e., apathy, aspontaneity, and indifference/emotional flatness). Brain magnetic resonance imaging in both patients showed atrophy of the midbrain tegmentum and superior medial frontal cortex suggestive of PSP, yet further evaluation of the neural correlates using multimodal neuroimaging and neuropathological data was not performed. However, based on the already known neural basis of DA and echolalia in PSP and stroke, we suggest that, in the present cases, neurodegeneration in the midbrain tegmentum, superior medial frontal lobe, and caudate nucleus was responsible for DA and that decreased activity in these regions may play a permissive role for eliciting verbal echoing via disinhibition of the perisylvian speech-language network.

Language in corticobasal syndrome: a systematic review

Language is commonly impacted in corticobasal syndrome (CBS). However, the profile and type of language assessment in CBS are poorly studied.

Phonemic fluency quantity and quality: Comparing patients with PSP, Parkinson's disease and focal frontal and subcortical lesions

Progressive supranuclear palsy (PSP) can be difficult to distinguish from Parkinson's disease (PD), but has a much graver prognosis. PSP is characterised severely reduced output on measures of phonemic fluency, suggesting that it may be a specific marker of PSP. However, reduced phonemic fluency has also been noted in PD, and very few studies have actually compared phonemic fluency in PSP and PD. Although anecdotal reports suggest that phonemic fluency output in PSP may have specific characteristics, with more low-frequency words and perseverative errors, no study to date has formally explored this. Further investigation into phonemic fluency output and its cognitive and neuroanatomical correlates is now critical for improving our understanding of the verbal fluency in PSP. In this study, we compared phonemic fluency characteristics (including quantity, frequency and error rates) in patients with PSP, PD and focal frontal or subcortical lesions, and age- and education-matched healthy controls. We then compared these characteristics with performance on extensive neuropsychological testing. We found that PSP patients generated significantly fewer words than patients with PD and patients with right frontal focal lesions, and healthy controls. Phonemic fluency was also significantly reduced in patients with left frontal and subcortical focal lesions. However, there were no significant group differences in word frequency or error rates. Phonemic fluency was best predicted by performance on the Vocabulary and Hayling neuropsychological tests. We argue that these findings provide important evidence that reduced phonemic fluency is a hallmark of PSP and argue that the specificity of this impairment betrays an underlying impairment in energization, reflecting dysfunction of left frontal and subcortical networks.

From discourse to pathology: Automatic identification of Parkinson's disease patients via morphological measures across three languages

Embodied cognition research on Parkinson's disease (PD) points to disruptions of frontostriatal language functions as sensitive targets for clinical assessment. However, no existing approach has been tested for crosslinguistic validity, let alone by combining naturalistic tasks with machine-learning tools. To address these issues, we conducted the first classifier-based examination of morphological processing (a core frontostriatal function) in spontaneous monologues from PD patients across three typologically different languages. The study comprised 330 participants, encompassing speakers of Spanish (61 patients, 57 matched controls), German (88 patients, 88 matched controls), and Czech (20 patients, 16 matched controls). All subjects described the activities they perform during a regular day, and their monologues were automatically coded via morphological tagging, a computerized method that labels each word with a part-of-speech tag (e.g., noun, verb) and specific morphological tags (e.g., person, gender, number, tense). The ensuing data were subjected to machine-learning analyses to assess whether differential morphological patterns could classify between patients and controls and reflect the former's degree of motor impairment. Results showed robust classification rates, with over 80% of patients being discriminated from controls in each language separately. Moreover, the most discriminative morphological features were associated with the patients' motor compromise (as indicated by Pearson r correlations between predicted and collected motor impairment scores that ranged from moderate to moderate-to-strong across languages). Taken together, our results suggest that morphological patterning, an embodied frontostriatal domain, may be distinctively affected in PD across languages and even under ecological testing conditions.

Differential patterns of internally generated responses in parkinsonian disorders

Internally generated responses are centrally affected in parkinsonian disorders. This study investigated the cognitive components crucial for response generation as reflected in performance on verbal and non-verbal fluency tasks, which require voluntary internal generation of multiple responses. Participants with parkinsonian disorders (N = 58: 29 Parkinson's disease [PD], 22 corticobasal syndrome [CBS], 8 progressive supranuclear palsy [PSP]) and 89 age-matched controls completed baseline cognitive assessments and eight fluency tasks of four types: word, design, gesture, and ideational. We analysed the total number of correct responses generated and error rates (including repetitions and rule breaks) for PD, CBS and Control groups. The small PSP patient group's performance is reported for comparative purposes only. CBS patients were significantly reduced in the number of correct responses generated across all fluency tasks, without incurring significant errors. The only exception was that CBS patients produced a significantly higher number of repetitions on one nonverbal task (design fluency). By contrast, PD patients' generation was reduced on only three fluency tasks (phonemic word, meaningless gesture, conventional idea). However, they also produced a high error rate on four fluency tasks (rule-break errors: phonemic/semantic word; repetitions: semantic word, meaningless gestures). Overall, the pattern of fluency task performance differs between patient groups. Specifically, the quantity of responses generated is differentially and primarily affected in CBS patients, whereas the quality of responses generated is primarily affected in PD patients. This suggests potentially different patterns of performance for parkinsonian disorders and has implications for the cognitive processes crucial for internally-guided response generation.

Developmental Dynamic Dysphasia: Are Bilateral Brain Abnormalities a Signature of Inefficient Neural Plasticity?

The acquisition and evolution of speech production, discourse and communication can be negatively impacted by brain malformations. We describe, for the first time, a case of developmental dynamic dysphasia (DDD) in a right-handed adolescent boy (subject D) with cortical malformations involving language-eloquent regions (inferior frontal gyrus) in both the left and the right hemispheres. Language evaluation revealed a markedly reduced verbal output affecting phonemic and semantic fluency, phrase and sentence generation and verbal communication in everyday life. Auditory comprehension, repetition, naming, reading and spelling were relatively preserved, but executive function was impaired. Multimodal neuroimaging showed a malformed cerebral cortex with atypical configuration and placement of white matter tracts bilaterally and abnormal callosal fibers. Dichotic listening showed right hemisphere dominance for language, and functional magnetic resonance imaging (fMRI) additionally revealed dissociated hemispheric language representation with right frontal activation for phonology and bilateral dominance for semantic processing. Moreover, subject D also had congenital mirror movements (CMM), defined as involuntary movements of one side of the body that mirror intentional movements of the other side. Transcranial magnetic stimulation and fMRI during voluntary unimanual (left and right) hand movements showed bilateral motor cortex recruitment and tractography revealed a lack of decussation of bilateral corticospinal tracts. Genetic testing aimed to detect mutations that disrupt the development of commissural tracts correlating with CMM (e.g., Germline DCC mutations) was negative. Overall, our findings suggest that DDD in subject D resulted from the underdevelopment of the left inferior frontal gyrus with limited capacity for plastic reorganization by its homologous counterpart in the right hemisphere. Corpus callosum anomalies probably contributed to hinder interhemispheric connectivity necessary to compensate language and communication deficits after left frontal involvement.