Abstract
Aims: This study aimed to investigate phoneme perception in patients with primary progressive aphasia (PPA) by using the event-related potential (ERP) technique. These ERP components might contribute to the diagnostic process of PPA and its clinical variants (NFV: nonfluent variant, SV: semantic variant, LV: logopenic variant) and reveal insights about phoneme perception processes in these patients.Method: Phoneme discrimination and categorization processes were investigated by the mismatch negativity (MMN) and P300 in eight persons with early- and late-stage PPA (3 NFV, 2 LV, 2 SV, and 1 PPA-NOS; not otherwise specified) and 30 age-matched healthy adults. The mean amplitude, the onset latency, and the topographic distribution of both components in each patient were compared to the results of the control group.Results: The MMN was absent or the onset latency of the MMN was delayed in the patients with the NFV, LV, and PPA-NOS in comparison to the control group. In contrast, no differences in mean amplitudes and onset latencies of the MMN were found between the patients with the SV and the control group. Concerning the P300, variable results were found in the patients with the NFV, SV, and PPA-NOS, but the P300 of both patients with the LV was delayed and prolonged with increased mean amplitude in comparison to the control group.Conclusion: In this preliminary study, phoneme discrimination deficits were found in the patients with the NFV and LV, and variable deficits in phoneme categorization processes were found in all patients with PPA. In clinical practice, the MMN might be valuable to differentiate the SV from the NFV and the LV and the P300 to differentiate the LV from the NFV and the SV. Further research in larger and independent patient groups is required to investigate the applicability of these components in the diagnostic process and to determine the nature of these speech perception deficits in the clinical variants of PPA.
Highlights
Primary progressive aphasia (PPA) refers to a heterogeneous group of neurodegenerative clinical syndromes in which a range of language and speech abilities progressively deteriorate with relative preservation of the other cognitive domains
The P300 was present in one patient with the early-stage nonfluent or agrammatic variant (NFV) and possibly present in one patient with the early-stage semantic variant (SV), these results indicate that deficits in phoneme categorization processes might be present in patients with the NFV, SV, and PPA-not otherwise specified (NOS)
This study only examined one phonemic contrast and in patients with aphasia differences in the MMN and P300 amplitudes were found depending on the phonemic contrasts (Aerts et al, 2015)
Summary
Primary progressive aphasia (PPA) refers to a heterogeneous group of neurodegenerative clinical syndromes in which a range of language and speech abilities progressively deteriorate with relative preservation of the other cognitive domains. An international group of researchers provided a framework for the diagnosis of PPA and its clinical variants (Gorno-Tempini et al, 2011). In this framework, diagnostic criteria for three clinical variants, namely the nonfluent or agrammatic variant (NFV), the semantic variant (SV), and the logopenic variant (LV), are provided. The NFV is characterized by the presence of agrammatism in language production, apraxia of speech (AOS), impaired comprehension of syntactically complex sentences, and spared single-word comprehension and object knowledge. The language pattern of the LV typically shows impaired single-word retrieval and impaired repetition of sentences and phrases In this variant, phonological errors could be present but the single-word comprehension, object knowledge, and motor speech production are mostly spared. The SV and NFV are most frequently associated with FTLD pathology and the LV with AD pathology, but other pathologies have been found as well (Davies et al, 2005; Kertesz et al, 2005; Amici et al, 2006; Grossman, 2010; Leyton and Ballard, 2016)
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