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Lexical Decision Task for Studying Written Word Recognition in Adults with and without Dementia or Mild Cognitive Impairment
Published on: June 25, 2019
Ever decreasing circles: Speech production in semantic dementia
Lotte Meteyard1, Emma Quain1, Karalyn Patterson2
1School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK.
Summary
Patients with semantic dementia (SD) exhibit reduced lexical, morphological, and syntactic complexity in speech. Their language production shows fewer low-frequency words and simpler grammatical structures compared to healthy individuals.
Area of Science:
- Neuroscience
- Linguistics
- Psychology
Background:
- Semantic dementia (SD) is a neurodegenerative condition affecting the anterior temporal lobes, leading to progressive loss of semantic knowledge.
- Understanding the impact of semantic deficits on language production is crucial for diagnosing and managing SD.
Purpose of the Study:
- To investigate how a degraded semantic system influences lexical, morphological, and syntactic complexity in language production.
- To compare speech patterns of patients with SD to age-matched healthy controls.
Main Methods:
- Analysis of connected speech samples from eight patients with SD and eight healthy controls.
- Comparison of frequency distributions of nouns and verbs using hand-scored and text-analysis software data.
- Examination of morpho-syntactic and syntactic constructions for complexity and range.
Main Results:
- Patients with SD showed fewer low-frequency nouns and verbs compared to controls in both scoring methods.
- The SD group exhibited a reduced range of complex morpho-syntactic forms, including fewer constructions with multiple auxiliaries and inflections.
- Syntactic constructions differed between groups, reflecting anomia and constraints on morpho-syntactic complexity in SD patients.
Conclusions:
- Language production in SD is characterized by alterations in lexical, morphological, and syntactic complexity, consistent with semantic impairment.
- Findings support constraint satisfaction models of speech production, suggesting a continuum between lexical retrieval and grammatical encoding.
- While gross syntactic errors are absent, the distribution of morphology and syntax is significantly affected in semantic dementia.
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