Insights into lexical-semantic processing from not only semantic but also non-fluent and logopenic primary progressive aphasia
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1
The Graduate Center, City University of New York, Speech-Language-Hearing Sciences, United States
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2
University of California San Francisco, Department of Neurology, Memory and Aging Center, United States
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3
University of Groningen, Netherlands
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4
Columbia University, Department of Neurology, Taub Institute for Research on Alzheimer’s Disease and the Aging Brain, United States
The extent to which semantic processing is required for lexical decision remains unclear. Two competing theories have emerged to explain word recognition: the connectionist triangle model (Plaut et al., 1996) and the Dual Route Cascaded (DRC) model (Coltheart et al., 2001). While no conceptual information is needed in the DRC model, it is required in the connectionist model. Hence, the models make opposing predictions about performance of individuals with semantic primary progressive aphasia (svPPA) on a lexical decision task. Yet, lexical decision performance of individuals with the non-fluent (nfvPPA) and logopenic (lvPPA) variants, supposedly characterized by intact single-word processing and no semantic impairment, has also shown below-normal performance in its few case and single-group investigations to date. Our study relating lexical decision and semantic processing in all three variants of PPA addresses 1) whether poor lexical decision performance is limited exclusively to individuals with svPPA and 2) whether semantic impairment and lexical decision performance are strongly linked.
We compared 41 individuals with nfvPPA (N = 13), lvPPA (N = 14), and svPPA (N = 14), as well as 25 age-matched controls, on lexical decision accuracy for 355 real words, carefully controlled on a broad range of psycholinguistic and semantic variables, and 175 pseudowords matched with the real words on psycholinguistic variables. Additionally, two non-verbal semantic tasks (Pyramids and Palm Trees test and Over-regular Object Test) were administered to assess semantic ability.
Mixed-model analyses showed that in lexical decision accuracy, all PPA groups were worse than the controls, with the largest contrast between controls and individuals with svPPA (p = .001) and smaller but significant differences in comparison to nfvPPA (p=.007) and lvPPA (p = .009). On the semantic tasks, individuals with svPPA scored significantly worse than those with nfvPPA (p = .003) and lvPPA (p = .004), while the latter two were approximately equal with little to no semantic impairment (p = .952). Semantic ability was a significant predictor of lexical decision accuracy across all individuals with PPA (B = -1.841, SE = .849, p = .030), but was not significant in separate models for any of the diagnoses due to large variances within each variant (nfvPPA: B = -.265, SE = 1.373, p = .847, lvPPA: B = 2.679, SE = 3.002, p = .369, svPPA: B = -1.685, SE = 1.197, p = .159).
Not only do the results show that individuals with all three PPA variants perform below normal on lexical decision, but also that semantic impairment alone does not sufficiently account for the variance in lexical decision performance within diagnoses—even though there is a solid overall relationship between lexical decision performance and semantic ability. The absence of a significant relation between lexical decision performance and semantic ability, especially in individuals with svPPA, favors the DRC model in which semantic activation is not necessary. Yet, the predictive value of semantic ability for lexical decision performance across all individuals with PPA—including those with nfvPPA and lvPPA—reveals an active role for semantic information in word recognition.
References
Coltheart, M., Rastle, K., Perry, C., Langdon, R., & Ziegler, J. (2001). DRC: A Dual Route Cascaded model of visual word recognition and reading aloud. Psychological Review, 108(1), 204.
Plaut, D. C., McClelland, J. L., Seidenberg, M. S., & Patterson, K. (1996). Understanding normal and impaired word reading: Computational principles in quasi-regular domains. Psychological Review, 103(1), 56.
Keywords:
primary progressive aphasia,
semantics,
lexical decision,
Dementia,
Comprehension
Conference:
Academy of Aphasia 55th Annual Meeting , Baltimore, United States, 5 Nov - 7 Nov, 2017.
Presentation Type:
poster or oral
Topic:
Consider for student award
Citation:
Vonk
J,
Gorno-Tempini
M,
Hubbard
H,
Jonkers
R,
Brickman
AM,
Miller
BL and
Obler
LK
(2019). Insights into lexical-semantic processing from not only semantic but also non-fluent and logopenic primary progressive aphasia.
Conference Abstract:
Academy of Aphasia 55th Annual Meeting .
doi: 10.3389/conf.fnhum.2017.223.00029
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Received:
03 May 2017;
Published Online:
25 Jan 2019.
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Correspondence:
Ms. Jet M. J. Vonk, The Graduate Center, City University of New York, Speech-Language-Hearing Sciences, New York, New York, 10016, United States, jet.vonk@ucsf.edu