Impairment of script comprehension in Lewy body spectrum disorders

Language impairment in Parkinson’s disease: fMRI study of sentence reading comprehension

Parkinson’s disease (PD) affects the language processes, with a significant impact on the patients’ daily communication. We aimed to describe specific alterations in the comprehension of syntactically complex sentences in patients with PD (PwPD) as compared to healthy controls (HC) and to identify the neural underpinnings of these deficits using a functional connectivity analysis of the striatum. A total of 20 patients PwPD and 15 HC participated in the fMRI study. We analyzed their performance of a Test of sentence comprehension (ToSC) adjusted for fMRI. A task-dependent functional connectivity analysis of the striatum was conducted using the psychophysiological interaction method (PPI). On the behavioral level, the PwPD scored significantly lower (mean ± sd: 77.3 ± 12.6) in the total ToSC score than the HC did (mean ± sd: 86.6 ± 8.0), p = 0.02, and the difference was also significant specifically for sentences with a non-canonical word order (PD-mean ± sd: 69.9 ± 14.1, HC-mean ± sd: 80.2 ± 11.5, p = 0.04). Using PPI, we found a statistically significant difference between the PwPD and the HC in connectivity from the right striatum to the supplementary motor area [SMA, (4 8 53)] for non-canonical sentences. This PPI connectivity was negatively correlated with the ToSC accuracy of non-canonical sentences in the PwPD. Our results showed disturbed sentence reading comprehension in the PwPD with altered task-dependent functional connectivity from the right striatum to the SMA, which supports the synchronization of the temporal and sequential aspects of language processing. The study revealed that subcortical-cortical networks (striatal-frontal loop) in PwPD are compromised, leading to impaired comprehension of syntactically complex sentences.

Neural basis of impaired narrative discourse comprehension in prodromal and mild dementia with lewy bodies

Narrative discourse (ND) comprehension is a complex task that implies not only linguistic abilities but also other cognitive abilities, including efficient executive functioning. An executive dysfunction has been described in dementia with Lewy bodies (DLB) from the early stage. Here, we question the link between executive dysfunction in DLB and narrative comprehension. The aim of our study was to evaluate ND comprehension and to investigate the neuroanatomical basis for its impairment in the early stage of DLB. DLB patients (N = 26) and controls (N = 19) underwent the ND comprehension test of the Montreal Protocol for Evaluation of Communication (MEC). An additional, qualitative analysis was conducted on their verbal productions. Cognitive tests assessing verbal episodic memory, executive functions, naming and oral syntactic comprehension were also performed. Brain gray matter correlates of the ND comprehension test were examined using voxel-based morphometry (VBM). An ND comprehension impairment was found for prodromal and mild DLB patients as compared to controls. These difficulties were correlated with the Frontal Assessment Battery (FAB) score. ND comprehension impairment in DLB was further characterized by a deficit in the organization and the logic of the discourse. Moreover, VBM analysis revealed a correlation between striatal gray matter volumes and DLB patients’ ability to extract and organize relevant information (p < 0.05, FDR correction, cluster level). The ND comprehension impairment in DLB patients could be related to their executive dysfunction through a deficit of information selection and organization that correlates with the volumetric reduction of striatal gray matter.

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.

The organization and anatomy of narrative comprehension and expression in Lewy body spectrum disorders

OBJECTIVE

Patients with Lewy body spectrum disorders (LBSD) such as Parkinson's disease, Parkinson's disease with dementia, and dementia with Lewy bodies exhibit deficits in both narrative comprehension and narrative expression. The present research examines the hypothesis that these impairments are due to a material-neutral deficit in organizational executive resources rather than to impairments of language per se. We predicted that comprehension and expression of narrative would be similarly affected and that deficits in both expression and comprehension of narrative would be related to the same anatomic distribution of prefrontal disease.

METHOD

We examined 29 LBSD patients and 26 healthy seniors on their comprehension and expression of narrative discourse. For comprehension, we measured accuracy and latency in judging events with high and low associativity from familiar scripts such as "going fishing." The expression task involved maintaining the connectedness of events while narrating a story from a wordless picture book.

RESULTS

LBSD patients were impaired on measures of narrative organization during both comprehension and expression relative to healthy seniors. Measures of organization during narrative expression and comprehension were significantly correlated with each other. These measures both correlated with executive measures but not with neuropsychological measures of lexical semantics or grammar. Voxel-based morphometry revealed overlapping regressions relating frontal atrophy to narrative comprehension, narrative expression, and measures of executive control.

CONCLUSIONS

Difficulty with narrative discourse in LBSD stems in part from a deficit of organization common to comprehension and expression. This deficit is related to prefrontal cortical atrophy in LBSD.