Heterogeneity and overlap in the continuum of linguistic profile of logopenic and semantic variants of primary progressive aphasia: a Profile Analysis based on Multidimensional Scaling study.

BACKGROUND: Primary progressive aphasia (PPA) diagnostic criteria underestimate the complex presentation of semantic (sv) and logopenic (lv) variants, in which symptoms partially overlap, and mixed clinical presentation (mixed-PPA) and heterogenous profile (lvPPA +) are frequent. Conceptualization of similarities and differences of these clinical conditions is still scarce. METHODS: Lexical, semantic, phonological, and working memory errors from nine language tasks of sixty-seven PPA were analyzed using Profile Analysis based on Multidimensional Scaling, which allowed us to create a distributed representation of patients' linguistic performance in a shared space. Patients had been studied with [18F] FDG-PET. Correlations were performed between metabolic and behavioral data. RESULTS: Patients' profiles were distributed across a continuum. All PPA, but two, presented a lexical retrieval impairment, in terms of reduced production of verbs and nouns. svPPA patients occupied a fairly clumped space along the continuum, showing a preponderant semantic deficit, which correlated to fusiform gyrus hypometabolism, while only few presented working memory deficits. Adjacently, lvPPA + presented a semantic impairment combined with phonological deficits, which correlated with metabolism in the anterior fusiform gyrus and posterior middle temporal gyrus. Starting from the shared phonological deficit side, a large portion of the space was occupied by all lvPPA, showing a combination of phonological, lexical, and working memory deficits, with the latter correlating with posterior temporo-parietal hypometabolism. Mixed PPA did not show unique profile, distributing across the space. DISCUSSION: Different clinical PPA entities exist but overlaps are frequent. Identifying shared and unique clinical markers is critical for research and clinical practice. Further research is needed to identify the role of genetic and pathological factors in such distribution, including also higher sample size of less represented groups.

Brain activation during processing of mouth actions in patients with disorders of consciousness.

In the past 2 decades, several attempts have been made to promote a correct diagnosis and possible restorative interventions in patients suffering from disorders of consciousness. Sensory stimulation has been proved to be useful in sustaining the level of arousal/awareness and to improve behavioural responsiveness with a significant effect on oro-motor functions. Recently, action observation has been proposed as a stimulation strategy in patients with disorders of consciousness, based on neurophysiological evidence that the motor cortex can be activated not only during action execution but also when actions are merely observed in the absence of motor output, or during listening to action sounds and speech. This mechanism is provided by the activity of mirror neurons. In the present study, a group of patients with disorders of consciousness (11 males, 4 females; median age: 55 years; age range: 19-74 years) underwent task-based functional MRI in which they had, in one condition, to observe and listen to the sound of mouth actions, and in another condition, to listen to verbs with motor or abstract content. In order to verify the presence of residual activation of the mirror neuron system, the brain activations of patients were compared with that of a group of healthy individuals (seven males, eight females; median age: 33.4 years; age range: 24-65 years) performing the same tasks. The results show that brain activations were lower in patients with disorders of consciousness compared with controls, except for primary auditory areas. During the audiovisual task, 5 out of 15 patients with disorders of consciousness showed only residual activation of low-level visual and auditory areas. Activation of high-level parieto-premotor areas was present in six patients. During the listening task, three patients showed only low-level activations, and six patients activated also high-level areas. Interestingly, in both tasks, one patient with a clinical diagnosis of vegetative state showed activations of high-level areas. Region of interest analysis on blood oxygen level dependent signal change in temporal, parietal and premotor cortex revealed a significant linear relation with the level of clinical functioning, assessed with coma recovery scale-revised. We propose a classification of the patient's response based on the presence of low-level and high-level activations, combined with the patient's functional level. These findings support the use of action observation and listening as possible stimulation strategies in patients with disorders of consciousness and highlight the relevance of combined methods based on functional assessment and brain imaging to provide more detailed neuroanatomical specificity about residual activated areas at both cortical and subcortical levels.

The neural substrates of transdiagnostic cognitive-linguistic heterogeneity in primary progressive aphasia.

BACKGROUND: Clinical variants of primary progressive aphasia (PPA) are diagnosed based on characteristic patterns of language deficits, supported by corresponding neural changes on brain imaging. However, there is (i) considerable phenotypic variability within and between each diagnostic category with partially overlapping profiles of language performance between variants and (ii) accompanying non-linguistic cognitive impairments that may be independent of aphasia magnitude and disease severity. The neurobiological basis of this cognitive-linguistic heterogeneity remains unclear. Understanding the relationship between these variables would improve PPA clinical/research characterisation and strengthen clinical trial and symptomatic treatment design. We address these knowledge gaps using a data-driven transdiagnostic approach to chart cognitive-linguistic differences and their associations with grey/white matter degeneration across multiple PPA variants. METHODS: Forty-seven patients (13 semantic, 15 non-fluent, and 19 logopenic variant PPA) underwent assessment of general cognition, errors on language performance, and structural and diffusion magnetic resonance imaging to index whole-brain grey and white matter changes. Behavioural data were entered into varimax-rotated principal component analyses to derive orthogonal dimensions explaining the majority of cognitive variance. To uncover neural correlates of cognitive heterogeneity, derived components were used as covariates in neuroimaging analyses of grey matter (voxel-based morphometry) and white matter (network-based statistics of structural connectomes). RESULTS: Four behavioural components emerged: general cognition, semantic memory, working memory, and motor speech/phonology. Performance patterns on the latter three principal components were in keeping with each variant's characteristic profile, but with a spectrum rather than categorical distribution across the cohort. General cognitive changes were most marked in logopenic variant PPA. Regardless of clinical diagnosis, general cognitive impairment was associated with inferior/posterior parietal grey/white matter involvement, semantic memory deficits with bilateral anterior temporal grey/white matter changes, working memory impairment with temporoparietal and frontostriatal grey/white matter involvement, and motor speech/phonology deficits with inferior/middle frontal grey matter alterations. CONCLUSIONS: Cognitive-linguistic heterogeneity in PPA closely relates to individual-level variations on multiple behavioural dimensions and grey/white matter degeneration of regions within and beyond the language network. We further show that employment of transdiagnostic approaches may help to understand clinical symptom boundaries and reveal clinical and neural profiles that are shared across categorically defined variants of PPA.

A Multimodal Approach for Clinical Diagnosis and Treatment of Primary Progressive Aphasia (MAINSTREAM): A Study Protocol.

Primary Progressive Aphasia (PPA) is a syndrome due to different neurodegenerative disorders selectively disrupting language functions. PPA specialist care is underdeveloped. There are very few specialists (neurologists, psychiatrists, neuropsychologists, and speech therapists) and few hospital- or community-based services dedicated to the diagnosis and continuing care of people with PPA. Currently, healthcare systems struggle to provide adequate coverage of care that is too often fragmented, uncoordinated, and unresponsive to the needs of people with PPA and their families. Recently, attention has been gained by non-invasive brain stimulation techniques that allow a personalized treatment approach, such as transcranial Direct Current Stimulation (tDCS). The MAINSTREAM trial looks forward to introducing and evaluating therapeutic innovations such as tDCS coupled with language therapy in rehabilitation settings. A Multimodal Approach for Clinical Diagnosis and Treatment of Primary Progressive Aphasia, MAINSTREAM (ID: 3430931) was registered in the clinicaltrials.gov database (identifier: NCT05730023) on 15 February 2023.

Comparing two picture naming tasks in primary progressive aphasia: Insights from behavioural and neural results.

Picture naming tests are widely used to evaluate language impairments in neurodegenerative diseases, especially in Primary Progressive Aphasia (PPA). The available tests differ for many factors affecting the performance, e.g. format of stimuli and their psycholinguistic properties. We aim to identify the most appropriate naming test to be used on PPA according to the clinical and research demands. We investigated the behavioural characteristics, i.e. proportion of correct responses and error type, and their neural correlates in two Italian naming tests, CaGi naming (CaGi) and naming subtest of the Screening for Aphasia in NeuroDegeneration battery (SAND), administered to 52 PPA patients who underwent an FDG-PET scan. We analysed the effectiveness of the tests in distinguishing PPA versus controls and among PPA variants, considering the psycholinguistic variables affecting performance. We explored the brain metabolic correlates of behavioural performance in the tests. SAND, differently from CaGi, has time limits for the response and its items are less frequent and acquired later. SAND and CaGi differed in terms of number of correct responses and error profile, suggesting a higher difficulty to name SAND items compared to CaGi. Semantic errors predominated in CaGi, while anomic and semantic errors were equally frequent in SAND. Both tests distinguished PPA from controls, but SAND outperformed CaGi in discriminating among PPA variants. FDG-PET imaging revealed a shared metabolic involvement of temporal areas associated with lexico-semantic processing, encompassing anterior fusiform, temporal pole, and extending to posterior fusiform in sv-PPA. Concluding, a picture naming test with response time limit and items which are less frequent and acquired later in life, as SAND, may be effective at highlighting subtle distinctions between PPA variants, improving the diagnosis. Conversely, a naming test without time limit for the response, as CaGi, may be useful for a better characterization of the nature of the naming impairment at the behavioural level, eliciting more naming errors than anomia, possibly helping in the development of rehabilitation protocols.

The Italian Sensorimotor Norms: Perception and action strength measures for 959 words.

Neuroscience research has provided evidence that semantic information is stored in a distributed brain network involved in sensorimotor and linguistic processing. More specifically, according to the embodied cognition accounts, the representation of concepts is deemed as grounded in our bodily states. For these reasons, normative measures of words should provide relevant information about the extent to which each word embeds perceptual and action properties. In the present study, we collected ratings for 959 Italian nouns and verbs from 398 volunteers, recruited via an online platform. The words were mostly taken from the Italian adaptation of the Affective Norms for English Words (ANEW). A pool of 145 verbs was added to the original set. All the words were rated on 11 sensorimotor dimensions: six perceptual modalities (vision, audition, taste, smell, touch, and interoception) and five effectors (hand-arm, foot-leg, torso, mouth, head). The new verbs were also rated on the ANEW dimensions. Results showed good reliability and consistency with previous studies. Relations between perceptual and motor dimensions are described and interpreted, along with relations between the sensorimotor and the affective dimensions. The currently developed dataset represents an important novelty, as it includes different word classes, i.e., both nouns and verbs, and integrates ratings of both sensorimotor and affective dimensions, along with other psycholinguistic parameters; all features only partially accomplished in previous studies.

Comprehensive qualitative characterization of linguistic performance profiles in primary progressive aphasia: a multivariate study with FDG-PET.

Primary progressive aphasia (PPA) classification relies on profile characterization of quantitatively impaired/spared performance in language tasks. In this study, we coextracted 8 qualitative types of errors in 67 PPA patients submitted to a comprehensive language assessment. Canonical correlation analysis was applied to simultaneously correlate qualitative errors and brain metabolism, collected with FDG-PET. Results showed the contribution of semantic, syntactic and working memory errors associated with specific correlates of regional metabolic changes. Reduced metabolism in the left fusiform gyrus, anterior-middle and inferior-temporal gyri and middle-temporal pole correlated with an increase of semantic errors. Hypometabolism in the left inferior, middle, and superior frontal gyri, insula and right middle-occipital gyrus was related to syntactic errors. Higher metabolism in the bilateral pallidum, putamen, and left thalamus, as well as hypometabolism in the left angular and supramarginal gyri, inferior-parietal lobule, posterior-middle and inferior-temporal gyri and posterior cingulum predicted the increase of working memory errors. A relevant role of working memory subcomponents was associated with distinct neural systems. Patients' profiles are easily represented in a qualitative multidimensional space, in which mixed PPA overlapped with different phenotypes.

Characterization of the logopenic variant of Primary Progressive Aphasia: A systematic review and meta-analysis.

The linguistic and anatomical variability of the logopenic variant of Primary Progressive Aphasia (lv-PPA) as defined by current diagnostic criteria has been the topic of an intense debate. The present review and meta-analysis aims at characterizing the profile of lv-PPA, by a comprehensive analysis of the available literature on the neuropsychological, neuroimaging, electrophysiological, pathological, and genetic features of lv-PPA. We conducted a systematic bibliographic search, leading to the inclusion of 207 papers. Of them, 12 were used for the Anatomical Likelihood Estimation meta-analysis on grey matter revealed by magnetic resonance imaging data. The results suggest that the current guidelines outline a relatively consistent syndrome, characterized by a core set of linguistic and, to a lesser extent, non-linguistic deficits, mirroring the involvement of left temporal and parietal regions typically affected by Alzheimer Disease pathology. Variations of the lv-PPA profile are discussed in terms of heterogeneity of the neuropsychological instruments and the diagnostic criteria adopted.

Italian adaptation of the Uniform Data Set Neuropsychological Test Battery (I-UDSNB 1.0): development and normative data.

BACKGROUND: Neuropsychological testing plays a cardinal role in the diagnosis and monitoring of Alzheimer's disease. A major concern is represented by the heterogeneity of the neuropsychological batteries currently adopted in memory clinics and healthcare centers. The current study aimed to solve this issue. METHODS: Following the initiative of the University of Washington's National Alzheimer's Coordinating Center (NACC), we presented the Italian adaptation of the Neuropsychological Test Battery of the Uniform Data Set (I-UDSNB). We collected data from 433 healthy Italian individuals and employed regression models to evaluate the impact of demographic variables on the performance, deriving the reference norms. RESULTS: Higher education and lower age were associated with a better performance in the majority of tests, while sex affected only fluency tests and Digit Span Forward. CONCLUSIONS: The I-UDSNB offers a valuable and harmonized tool for neuropsychological testing in Italy, to be used in clinical and research settings.

Brain metabolic connectivity reconfiguration in the semantic variant of primary progressive aphasia.

Functional network-level alterations in the semantic variant of Primary Progressive Aphasia (sv-PPA) are relevant to understanding the clinical features and the neural spreading of the pathology. We assessed the effect of neurodegeneration on brain systems reorganization in early sv-PPA, using advanced brain metabolic connectivity approaches. Forty-four subjects with sv-PPA and forty-four age-matched healthy controls (HC) were included. We applied two multivariate approaches to [18F]FDG-PET data - i.e., sparse inverse covariance estimation and seed-based interregional correlation analysis - to assess the integrity of (i) the whole-brain metabolic connectivity and (ii) the connectivity of brain regions relevant for cognitive and behavioral functions. Whole-brain analysis revealed a global-scale connectivity reconfiguration in sv-PPA, with widespread changes in metabolic connections of frontal, temporal, and parietal regions. In comparison to HC, the seed-based analysis revealed a) functional isolation of the left anterior temporal lobe (ATL), b) decreases in temporo-occipital connections and contralateral homologous regions, c) connectivity increases to the dorsal parietal cortex from the spared posterior temporal cortex, d) a disruption of the large-scale limbic brain networks. In sv-PPA, the severe functional derangement of the left ATL may lead to an extensive connectivity reconfiguration, encompassing several brain regions, including those not yet affected by neurodegeneration. These findings support the hypothesis that in sv-PPA the focal vulnerability of the core region (i.e., ATL) can potentially drive the widespread cerebral connectivity changes, already present in the early phase.

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.

In search of different categories of abstract concepts: a fMRI adaptation study.

Concrete conceptual knowledge is supported by a distributed neural network representing different semantic features according to the neuroanatomy of sensory and motor systems. If and how this framework applies to abstract knowledge is currently debated. Here we investigated the specific brain correlates of different abstract categories. After a systematic a priori selection of brain regions involved in semantic cognition, i.e. responsible of, respectively, semantic representations and cognitive control, we used a fMRI-adaptation paradigm with a passive reading task, in order to modulate the neural response to abstract (emotions, cognitions, attitudes, human actions) and concrete (biological entities, artefacts) categories. Different portions of the left anterior temporal lobe responded selectively to abstract and concrete concepts. Emotions and attitudes adapted the left middle temporal gyrus, whereas concrete items adapted the left fusiform gyrus. Our results suggest that, similarly to concrete concepts, some categories of abstract knowledge have specific brain correlates corresponding to the prevalent semantic dimensions involved in their representation.

The language profile in multiple system atrophy: an exploratory study.

BACKGROUND: The evidence about the language performance profile of multiple system atrophy (MSA) is limited, but its definition may lead to a more comprehensive characterization of the disorder and contribute to clarify the involvement of the basal ganglia in language abilities. OBJECTIVE: The objectives of the study were: (1) to evaluate the reliability of the Screening for Aphasia in NeuroDegeneration (SAND) in MSA patients; (2) compare the linguistic profiles among MSA and Parkinson's disease (PD) patients and healthy controls (HC), and (3) assess relationships between language impairment and cognitive status and MSA motor subtypes. METHODS AND RESULTS: Forty patients with a diagnosis of MSA, 22 HC and 17 patients with PD were enrolled in the present study. By excluding the writing task that showed a poor acceptability, we showed that the MSA-tailored SAND Global Score is an acceptable, consistent and reliable tool to screen language disturbances in MSA. MSA patients performed worse than HC, but not than PD, in MSA-tailored SAND Global Score, repetition, reading and semantic association tasks. We did not find significant differences between MSA phenotypes. MSA patients with mild cognitive impairment-multiple domain presented worse language performances as compared to MSA patients with normal cognition and mild cognitive impairment-single domain. CONCLUSION: The MSA-tailored SAND Global Score is a consistent and reliable tool to screen language disturbances in MSA. Language disturbances characterize MSA patients irrespective of disease phenotype, and parallel the decline of global cognitive functions.

Corrigendum: Preservation of Language Processing and Auditory Performance in Patients With Disorders of Consciousness: A Multimodal Assessment.

[This corrects the article DOI: 10.3389/fneur.2020.526465.].

Neural correlates of naming errors across different neurodegenerative diseases: An FDG-PET study.

OBJECTIVE: To investigate the types of errors produced in a picture naming task by patients with neurodegenerative dementia due to different etiologies and their neural correlates. METHODS: The same standardized picture naming test was administered to a consecutive sample of patients (n = 148) who had been studied with [18F] FDG-PET. The errors were analyzed in 3 categories (visual, semantic, and phonologic). The PET data were analyzed using an optimized single-subject procedure, and the statistical parametric mapping multiple regression design was used to explore the correlation between each type of error and brain hypometabolism in the whole group. Metabolic connectivity analyses were run at the group level on 7 left hemisphere cortical areas corresponding to an a priori defined naming network. RESULTS: Semantic errors were predominant in most patients, independent of clinical diagnosis. In the whole group analysis, visual errors correlated with hypometabolism in the right inferior occipital lobe and in the left middle occipital lobe. Semantic errors correlated with hypometabolism in the left fusiform gyrus, the inferior and middle temporal gyri, and the temporal pole. Phonologic errors were associated with hypometabolism in the left superior and middle temporal gyri. Both positive (occipital-posterior fusiform) and negative (anterior fusiform gyrus and the superior anterior temporal lobe) connectivity changes were associated with semantic errors. CONCLUSIONS: Naming errors reflect the dysfunction of separate stages of the naming process and are specific markers for different patterns of brain involvement. These correlations are not limited to primary progressive aphasia but extend to other neurodegenerative dementias.

High gamma response tracks different syntactic structures in homophonous phrases.

Syntax is a species-specific component of human language combining a finite set of words in a potentially infinite number of sentences. Since words are by definition expressed by sound, factoring out syntactic information is normally impossible. Here, we circumvented this problem in a novel way by designing phrases with exactly the same acoustic content but different syntactic structures depending on the other words they occur with. In particular, we used phrases merging an article with a noun yielding a Noun Phrase (NP) or a clitic with a verb yielding a Verb Phrase (VP). We performed stereo-electroencephalographic (SEEG) recordings in epileptic patients. We measured a different electrophysiological correlates of verb phrases vs. noun phrases in multiple cortical areas in both hemispheres, including language areas and their homologous in the non-dominant hemisphere. The high gamma band activity (150-300 Hz frequency), which plays a crucial role in inter-regional cortical communications, showed a significant difference during the presentation of the homophonous phrases, depending on whether the phrase was a verb phrase or a noun phrase. Our findings contribute to the ultimate goal of a complete neural decoding of linguistic structures from the brain.

Preservation of Language Processing and Auditory Performance in Patients With Disorders of Consciousness: A Multimodal Assessment.

The impact of language impairment on the clinical assessment of patients suffering from disorders of consciousness (DOC) is unknown or underestimated and may mask the presence of conscious behavior. In a group of DOC patients (n = 11; time post-injury range: 5-252 months), we investigated the main neural functional and structural underpinnings of linguistic processing, and their relationship with the behavioral measures of the auditory function using the Coma Recovery Scale-Revised (CRS-R). We assessed the integrity of the brainstem auditory pathways, of the left superior temporal gyrus and arcuate fasciculus, the neural activity elicited by passive listening of an auditory language task, and the mean hemispheric glucose metabolism. Our results support the hypothesis of a relationship between the level of preservation of the investigated structures/functions and the CRS-R auditory subscale scores. Moreover, our findings indicate that patients in minimally conscious state minus (MCS-): (1) when presenting the auditory startle (at the CRS-R auditory subscale) might be aphasic in the receptive domain, being severely impaired in the core language structures/functions; (2) when presenting the localization to sound might retain language processing, being almost intact or intact in the core language structures/functions. Despite the small group of investigated patients, our findings provide a grounding of the clinical measures of the CRS-R auditory subscale in the integrity of the underlying auditory structures/functions. Future studies are needed to confirm our results that might have important consequences for the clinical practice.

State-dependent TMS reveals the differential contribution of ATL and IPS to the representation of abstract concepts related to social and quantity knowledge.

The neural representation of abstract concepts is a current matter of debate. While social concepts have been associated to superior anterior temporal lobe (sATL), the neural correlates of quantity-related concepts have seldom been investigated. The right intraparietal sulcus (IPS) is known to be involved in the processing of numerical information and of quantifiers. In the present study, we investigated the causal role of right sATL and right IPS in representing social and quantity-related concepts, using a state-dependent transcranial magnetic stimulation (TMS)-priming paradigm. We modulated the neural activation by priming to a category label (either SOCIAL or QUANTITY), before applying TMS and presenting the target (i.e., an exemplar of one of the two abstract classes). When the target word belonged to the quantity category, TMS applied over the IPS (but not sATL) abolished the expected priming effect by speeding up reaction times (RTs) in incongruent trials. For the social category, both IPS and sATL stimulation abolished the priming effect, by reducing RTs in incongruent trials. Our results suggest a specialization of distinct brain areas in processing different classes of abstract concepts. The right IPS contains neuronal representations tuned to quantity-related concepts, in line with its well-known role in numerical and magnitude representation. Social concepts, in contrast, are represented in both the right sATL and the right IPS, known to be involved in social cognition and person-related knowledge.