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The effect of semantic memory deficits on global coherence: An analysis of the discourse of patients with the semantic variant of primary progressive aphasia

Bruna Seixas Lima1, 2*, Naida L. Graham1, 2, Carol Leonard1, 3, Brian Levine4, 5, 6, Sandra E. Black1, 5, 6, 7, 8, 9, 10, 11, David Tang-Wai1, 12, Morris Freedman5, 6, 13 and Elizabeth Rochon1, 2
  • 1 University of Toronto, Department of Speech-Language Pathology, Canada
  • 2 University Health Network (TRI-UHN), Toronto Rehabilitation Institute, Canada
  • 3 University of Ottawa, Audiology and Speech-Language Pathology Program, Canada
  • 4 University of Toronto, Department of Psychology, Canada
  • 5 University of Toronto, Department of Medicine (Neurology), Canada
  • 6 Rotman Research Institute–Baycrest Centre, Canada
  • 7 Sunnybrook Health Sciences Centre, Canada
  • 8 University of Toronto, Institute of Medical Science, Canada
  • 9 Sunnybrook Health, Sciences Centre, L.C. Campbell Cognitive Neurology Research Unit, Canada
  • 10 Sunnybrook Research Institute, Brain Sciences Research Program, Canada
  • 11 Partnership for Stroke Recovery, Heart and Stroke Foundation, Canada
  • 12 University Health Network (TWH-UHN), Toronto Western Hospital, Canada
  • 13 Baycrest Centre, Centre for Memory and Neurotherapeutics, Canada

Global coherence (the interrelatedness of propositions in the underlying semantic representation of a topic) is a macro-linguistic feature necessary for the continuity of discourse. Macro-linguistic features are responsible for the semantic and pragmatic aspects of language. Global coherence in the discourse of individuals with the semantic variant of primary progressive aphasia (svPPA) has received scant attention in the literature. This study examined the effect of semantic memory deficits on global coherence in the discourse of these patients. In this study, 19 participants (10 svPPA, 9 controls) were asked personal questions which generated extended stretches of discourse (Orange et al., 1998; Koppelman et al., 1990). Participants’ answers were transcribed and segmented into utterances. The content of the segmented utterances was analysed using a scale we developed to measure coherence within a semantic frame: a subsystem of knowledge about phenomena in the world (Van Dijk, 1977). The scale ranged from A to D. An utterance was coded as: A if it represented an element of the frame; B if it was a relevant implication of the frame; C if it was neither an element of the frame nor relevant to the topic; and D if it was devoid of content. Participants’ interviews were also analysed using an adaptation of the Autobiographical Interview (AI) (Levine et al., 2002), to investigate semantic and episodic memory. The segmented utterances were categorized as episodic memory details (recollection of an event from a specific time and place) or semantic memory details (general knowledge about the world or the self). Since svPPA patients’ impairment is believed to be related to semantic memory deficits, it was hypothesised that the patients’ discourse would be more coherent in the segments demonstrating episodic re-experiencing (episodic details) than when demonstrating general knowledge (semantic details). Independent samples t-tests showed that patients produced significantly fewer episodic details than controls, but there was no significant difference in the number of semantic details produced by the two groups. Confirming our hypothesis, despite the lack of difference between groups with respect to the number of semantic details, patients produced significantly fewer coherent semantic details than controls. Furthermore, although controls produced more episodic details than patients, there was no significant difference between the two groups with respect to the number of coherent episodic details. Another analysis on utterances which could not be categorised as either episodic or semantic, and which were labelled as either metacognitive statements (e.g., “I can’t remember”) or discourse cues (e.g., “to make a long story short”) was carried out. Independent samples t-tests showed a similar pattern: although patients produced more of these statements, they were equally coherent between participant groups. These results suggest that the semantic memory system specifically may be affecting the deterioration of the coherence of svPPA’s patients’ discourse when reporting autobiographical memories, as this type of utterance exclusively contained incoherent information. A longitudinal analysis is currently in progress in order to investigate whether discourse coherence and memory decline will follow a similar pattern as the disease progresses.

References

Levine, B., Svoboda, E., Hay, J.F., Winocur, G., Moscovitch, M. (2002). Aging and autobiographical memory: dissociating episodic from semantic retrieval. Psychology and Aging, 17; 677-689.
Kopelman, M., Wilson, B. A., Baddeley, A. D. (1990). The Autobiographical Memory Interview. Thurston, Suffolk, England: Thames Valley Test Company.
Orange, J., Kertesz, A., Peacock, J. (1998). Pragmatics in frontal lobe dementia and primary progressive aphasia. Journal of Neurolinguistics, Vol. 11 n. 1-2, 153-177.
Van Dijk, T. (1977). In Text and Context: Explorations in the semantics and pragmatics of discourse. New York, Longman Linguistics Library.

Keywords: Language, Dementia, Semantic Dementia, primary progressive aphasia, discourse, coherence, Memory, autobiographical memory, Semantic memory, episodic memory

Conference: 54th Annual Academy of Aphasia Meeting, Llandudno, United Kingdom, 16 Oct - 18 Oct, 2016.

Presentation Type: Poster Sessions

Topic: Academy of Aphasia

Citation: Seixas Lima B, Graham NL, Leonard C, Levine B, Black SE, Tang-Wai D, Freedman M and Rochon E (2016). The effect of semantic memory deficits on global coherence: An analysis of the discourse of patients with the semantic variant of primary progressive aphasia. Front. Psychol. Conference Abstract: 54th Annual Academy of Aphasia Meeting. doi: 10.3389/conf.fpsyg.2016.68.00073

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Received: 29 Apr 2016; Published Online: 15 Aug 2016.

* Correspondence: Ms. Bruna Seixas Lima, University of Toronto, Department of Speech-Language Pathology, Toronto, ON, M5G 1V7, Canada, bruna.seixas.lima@gmail.com