Connected speech as a marker of disease progression in autopsy-proven Alzheimer’s disease

Abstract

Although an insidious history of episodic memory difficulty is a typical presenting symptom of Alzheimer’s disease, detailed neuropsychological profiling frequently demonstrates deficits in other cognitive domains, including language. Previous studies from our group have shown that language changes may be reflected in connected speech production in the earliest stages of typical Alzheimer’s disease. The aim of the present study was to identify features of connected speech that could be used to examine longitudinal profiles of impairment in Alzheimer’s disease. Samples of connected speech were obtained from 15 former participants in a longitudinal cohort study of ageing and dementia, in whom Alzheimer’s disease was diagnosed during life and confirmed at post-mortem. All patients met clinical and neuropsychological criteria for mild cognitive impairment between 6 and 18 months before converting to a status of probable Alzheimer’s disease. In a subset of these patients neuropsychological data were available, both at the point of conversion to Alzheimer’s disease, and after disease severity had progressed from the mild to moderate stage. Connected speech samples from these patients were examined at later disease stages. Spoken language samples were obtained using the Cookie Theft picture description task. Samples were analysed using measures of syntactic complexity, lexical content, speech production, fluency and semantic content. Individual case analysis revealed that subtle changes in language were evident during the prodromal stages of Alzheimer’s disease, with two-thirds of patients with mild cognitive impairment showing significant but heterogeneous changes in connected speech. However, impairments at the mild cognitive impairment stage did not necessarily entail deficits at mild or moderate stages of disease, suggesting non-language influences on some aspects of performance. Subsequent examination of these measures revealed significant linear trends over the three stages of disease in syntactic complexity, semantic and lexical content. The findings suggest, first, that there is a progressive disruption in language integrity, detectable from the prodromal stage in a subset of patients with Alzheimer’s disease, and secondly that measures of semantic and lexical content and syntactic complexity best capture the global progression of linguistic impairment through the successive clinical stages of disease. The identification of disease-specific language impairment in prodromal Alzheimer’s disease could enhance clinicians’ ability to distinguish probable Alzheimer’s disease from changes attributable to ageing, while longitudinal assessment could provide a simple approach to disease monitoring in therapeutic trials.

P2‐251: Visuoconstructional Impairment in Subtypes of Mild Cognitive Impairment

“…Libon et al (1996) found that performance in the command condition correlated with neuropsychological tests of semantic memory and language, whereas copy test performance was associated with executive and visuoconstructional measures. These findings are in accordance with evidence for significant semantic memory impairment in preclinical Alzheimer disease (Delano-Wood et al, 2009) as well as more recent evidence suggesting impaired lexical retrieval in preclinical Alzheimer disease (Ahmed et al, 2013). Other research examining performance on verbally mediated executive tests has clearly linked better performance on executive tests with relatively good performance on the BNT and the "animal" fluency tests, the language-related measures used in the current research (Bondi et al, 2002).…”

“…Other research examining performance on verbally mediated executive tests has clearly linked better performance on executive tests with relatively good performance on the BNT and the "animal" fluency tests, the language-related measures used in the current research (Bondi et al, 2002). Lou (1999) has also suggested that the alterations in response set can occur when verbally mediated executive tests require language-related abilities (Ahmed et al, 2013;Weakley, Schmitter-Edgecombe, & Anderson, 2013).…”

Motor speech signature of behavioral variant frontotemporal dementia

“…18 With a few exceptions, 23 acoustic analysis and subsequent objective differentiation of bvFTD and PPA speech profiles is not widely pursued as characterization in the dementias continues to rely on subjective clinical judgment. This may be mainly for practical reasons, as examiners tend to make clinician-based judgments, sometimes strengthened by semiquantitative analysis of connected speech (e.g., error rates, syntactic complexity, lexical and semantic content 38,39 ). Findings from this study demonstrate the utility of combining objective and listener-based judgements of speech by describing the speech signature of bvFTD.…”

Language in Amnestic Mild Cognitive Impairment and Dementia of Alzheimer’s Type: Quantitatively or Qualitatively Different?

“…The literature on lvPPA and language decline in dementia provides information on how language impairments, and connected speech in particular [18], interfere with cognitive function and thus can serve as a marker in dementia diagnosis. However, less is understood about the more general decline of language and its possible diagnostic value in MCI.…”