A disabling impairment of higher-order language function can be seen in patients with Lewy body spectrum disorders such as Parkinson's disease (PD), Parkinson's disease dementia (PDD), and dementia with Lewy bodies (DLB). We focus on script comprehension in patients with Lewy body spectrum disorders. While scripts unfold sequentially, constituent events are thought to contain an internal organization. Executive dysfunction in patients with Lewy body spectrum disorders may interfere with comprehension of this internal structure. We examined 42 patients (30 non-demented PD and 12 mildly demented PDD/DLB patients) and 12 healthy seniors. We presented 22 scripts (e.g., “going fishing”), each consisting of six events. Pilot data from young controls provided the basis for organizing associated events into clusters and arranging them hierarchically into scripts. We measured accuracy and latency to judge the order of adjacent events in the same cluster versus adjacent events in different clusters. PDD/DLB patients were less accurate in their ordering judgments than PD patients and controls. Healthy seniors and PD patients were significantly faster to judge correctly the order of highly associated within-cluster event pairs relative to less closely associated different-cluster event pairs, while PDD/DLB patients did not consistently distinguish between these event-pair types. This relative insensitivity to the clustered-hierarchical organization of events was related to executive impairment and to frontal atrophy as measured by volumetric MRI. These findings extend prior work on script processing to patients with Lewy body spectrum disorders and highlight the potential impact of frontal/executive dysfunction on the daily lives of affected patients.
Parkinson's disease; Parkinson's disease dementia; Dementia with Lewy bodies; Frontal cortex; Executive function; Scripts; Organization; Discourse; Volumetric MRI
Patients with Alzheimer’s disease have category-specific semantic memory difficulty for natural relative to manufactured objects. We assessed the basis for this deficit by asking healthy adults and patients to judge whether pairs of words share a feature (e.g. “banana:lemon – COLOR”). In an fMRI study, healthy adults showed gray matter (GM) activation of temporal-occipital cortex (TOC) where visual-perceptual features may be represented, and prefrontal cortex (PFC) which may contribute to feature selection. Tractography revealed dorsal and ventral stream white matter (WM) projections between PFC and TOC. Patients had greater difficulty with natural than manufactured objects. This was associated with greater overlap between diseased GM areas correlated with natural kinds in patients and fMRI activation in healthy adults for natural than manufactured artifacts, and the dorsal WM projection between PFC and TOC in patients correlated only with judgments of natural kinds. Patients thus remained dependent on the same neural network as controls during judgments of natural kinds, despite disease in these areas. For manufactured objects, patients’ judgments showed limited correlations with PFC and TOC GM areas activated by controls, and did not correlate with the PFC-TOC dorsal WM tract. Regions outside of the PFC–TOC network thus may help support patients’ judgments of manufactured objects. We conclude that a large-scale neural network for semantic memory implicates both feature knowledge representations in modality-specific association cortex and heteromodal regions important for accessing this knowledge, and that patients’ relative deficit for natural kinds is due in part to their dependence on this network despite disease in these areas.
semantic; fMRI; DTI; Alzheimer’s; temporal; prefrontal
Patients with Lewy body spectrum disorders (LBSD) such as Parkinson’s disease (PD), Parkinson’s disease with dementia (PDD), and dementia with Lewy bodies (DLB) 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.
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.
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.
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.
Parkinson’s disease; speech; language; dementia with Lewy bodies
Prior work has related sentence processing to executive deficits in non-demented patients with Parkinson’s disease (PD). We extended this investigation to patients with dementia with Lewy bodies (DLB) and PD dementia (PDD) by examining grammatical and working memory components of sentence processing in the full range of patients with Lewy body spectrum disorder (LBSD). Thirty-three patients with LBSD were given a two-alternative, forced-choice sentence-picture matching task. Sentence type, working memory, and grammatical structure were systematically manipulated in the sentences. We found that patients with PDD and DLB were significantly impaired relative to non-demented PD patients and healthy controls. The deficit in PDD/DLB was most pronounced for sentences lengthened by the strategic placement of an additional prepositional phrase and for sentences with an additional proposition due to a center-embedded clause. However, there was no effect for subject-relative versus object-relative grammatical structure. An MRI voxel-based morphometry analysis in a subset of patients showed significant gray matter thinning in the frontal lobe bilaterally, and this extended to temporal, parietal and occipital regions. A regression analysis related sentence processing difficulty in LBSD to frontal neocortex, including inferiorprefrontal, premotor, and dorsolateral prefrontal regions, as well as right superior temporal cortex. These findings are consistent with the hypothesis that patients with PDD and DLB have difficulty processing sentences with increased working memory demands and that this deficit is related in part to their frontal disease.
Lewy body; Parkinson’s; sentence processing; working memory; MRI; prefrontal
Previous work investigating deficits in self-appraisal in behavioural-variant frontotemporal degeneration (bvFTD) has focused on a single domain: social/behavioural processes. We examined whether a domain-specific versus multi-domain model best explains degraded self-appraisal in bvFTD.
49 patients with bvFTD and 73 patients with Alzheimer’s disease (AD) were administered quantitative assessments of episodic memory, naming and grammatical comprehension. Self-appraisal of cognitive test performance was assessed by asking patients to rate their performance immediately after completing each neuropsychological test. A discrepancy score was created to reflect the difference between patient performance on neuropsychological tests and self-appraisal of their test performance. Self-appraisal for each neuropsychological measure was related to grey matter (GM) density in each group using voxel-based morphometry.
bvFTD patients were poor at evaluating their own performance on all cognitive tests, with no significant correlations between self-appraisal and actual performance. By contrast, poor self-appraisal in AD was restricted to episodic memory performance. Poor self-appraisal on each task in bvFTD and AD was related to reduced GM density in several ventral and rostral medial prefrontal regions. Crucially, poor self-appraisal for all domains in bvFTD was related to a specific area of reduced GM density in the subgenual cingulate (BA 25).
Poor self-appraisal in bvFTD affects multiple domains, and this multi-domain impairment pattern is associated with frontal disease in the subgenual cingulate.
While grammatical aspects of language are preserved, executive deficits are prominent in Lewy body spectrum disorder (LBSD), including Parkinson’s disease (PD), Parkinson’s dementia (PDD) and dementia with Lewy bodies (DLB). We examined executive control during sentence processing in LBSD by assessing temporary structural ambiguities. Using an on-line word detection procedure, patients heard sentences with a syntactic structure that has high-compatibility or low-compatibility with the main verb’s statistically preferred syntactic structure, and half of the sentences were lengthened strategically between the onset of the ambiguity and its resolution. We found selectively slowed processing of lengthened ambiguous sentences in the PDD/DLB subgroup. This correlated with impairments on measures of executive control. Regression analyses related the working memory deficit during ambiguous sentence processing to significant cortical thinning in frontal and parietal regions. These findings emphasize the role of prefrontal disease in the executive limitations that interfere with processing ambiguous sentences in LBSD.
Parkinson’s; Lewy body; syntactic ambiguity; working memory; frontal
Quantifiers are very common in everyday speech, but we know little about their cognitive basis or neural representation. The present study examined comprehension of three classes of quantifiers that depend on different cognitive components in patients with focal neurodegenerative diseases. Patients evaluated the truth-value of a sentence containing a quantifier relative to a picture illustrating a small number of familiar objects, and performance was related to MRI grey matter atrophy using voxel-based morphometry. We found that patients with corticobasal syndrome (CBS) and posterior cortical atrophy (PCA) are significantly impaired in their comprehension of Cardinal Quantifiers (e.g. “At least three birds are on the branch”), due in part to their deficit in quantity knowledge. MRI analyses related this deficit to temporal-parietal atrophy found in CBS/PCA. We also found that patients with behavioral variant frontotemporal dementia (bvFTD) are significantly impaired in their comprehension of Logical Quantifiers (e.g. “Some the birds are on the branch”), associated with a simple form of perceptual logic, and this correlated with their deficit on executive measures. This deficit was related to disease in rostral prefrontal cortex in bvFTD. These patients were also impaired in their comprehension of Majority Quantifiers (e.g. “At least half of the birds are on the branch”), and this too was correlated with their deficit on executive measures. This was related to disease in the basal ganglia interrupting a frontal-striatal loop critical for executive functioning. These findings suggest that a large-scale frontal-parietal neural network plays a crucial role in quantifier comprehension, and that comprehension of specific classes of quantifiers may be selectively impaired in patients with focal neurodegenerative conditions in these areas.
comprehension; quantifier; parietal; frontal; corticobasal; frontotemporal dementia
Narrative discourse is an essential component of day-to-day communication, but little is known about narrative in Lewy Body spectrum disorder (LBSD), including Parkinson's disease (PD), Parkinson's disease with dementia (PDD), and dementia with Lewy bodies (DLB). We performed a detailed analysis of a semi-structured speech sample in 32 non-aphasic patients with LBSD, and we related their narrative impairments to gray matter (GM) atrophy using voxel-based morphometry. We found that patients with PDD and DLB have significant difficulty organizing their narrative speech. This was correlated with deficits on measures of executive functioning and speech fluency. Regression analyses associated this deficit with reduced cortical volume in inferior frontal and anterior cingulate regions. These findings are consistent with a model of narrative discourse that includes executive as well as language components and with an impairment of the organizational component of narrative discourse in patients with PDD and DLB.
Parkinson's disease; discourse; speech; language; Dementia with Lewy bodies
The Philadelphia Brief Assessment of the Cognition (PBAC) is a brief dementia-screening instrument. The PBAC assesses five cognitive domains: working memory/executive control; lexical retrieval/language; visuospatial/visuoconstructional operations; verbal/visual episodic memory; and behavior/social comportment. A revised version of the PBAC was administered to 198 participants including patients with Alzheimer’s disease (AD) (n=46) and four groups of patients with frontotemporal dementia (FTD) syndromes: behavioral-variant FTD (bvFTD; n=65), semantic-variant primary progressive aphasia (PPA) (svPPA; n=22), non-fluent/agrammatic-variant PPA (nfaPPA; n=23), and corticobasal syndrome (CBS; n=42), and a group of normal controls (n=15). The total PBAC score was highly correlated with the MMSE. The criterion validity of the PBAC was assessed relative to standard neuropsychological test performance. Using standard neuropsychological test performance as a criterion, the total PBAC score accurately identified the presence and severity of dementia. Intra-class correlations between PBAC subscales and standard neuropsychological tests were highly significant. PBAC subscales demonstrated good clinical utility in distinguishing AD and FTD subtypes using receiver operating characteristic analysis and standard diagnostic performance statistics to determine optimal subscale cut scores. The PBAC is a valid tool and able to assesses differential patterns neuropsychological/behavioral impairment in a broad range of neurodegenerative conditions.
Alzheimer’s disease; Frontotemporal lobar dementia; Frontotemporal dementia; FTD; Philadelphia Brief Assessment of the Cognition; PBAC; Neuropsychological assessment; Philadelphia (repeatable) Verbal Learning Test