Lexical access in semantic variant PPA: Evidence for a post-semantic contribution to naming deficits

Abstract

The most salient clinical symptom of semantic variant primary progressive aphasia (PPA) is a profound and pervasive anomia. These patients' naming impairments have been shown to reflect in large part a domain-general deterioration of conceptual knowledge that impacts both linguistic and non-linguistic processing. However, it is possible that post-semantic stages of lexical access may also contribute to naming deficits. To clarify the stages at which lexical access breaks down in semantic variant PPA, eleven French-speaking patients were asked to name objects, and were then queried for semantic, lexical-syntactic, and word form information pertaining to the items they could not name. Specifically, our goal was to determine whether patients can access intermediate representations known as lemmas, which mediate the arbitrary mapping between semantic representations and word forms (phonological and orthographic forms). The French language was chosen for this study because nouns in French are marked for grammatical gender, a prototypical type of lexical-syntactic information, represented at the level of the lemma. Access to word form information is also dependent on lemma access under some theoretical views. We found that six of the eleven patients showed partial access to either lexical-syntactic properties of unnamed items (grammatical gender), word form information (initial letter), or both. Access to these types of information suggests that a lemma has been retrieved, implying a breakdown at the post-semantic stage of word form retrieval. Our results suggest that although degraded conceptual knowledge is the main cause of naming deficits in semantic variant PPA, in some patients, a post-semantic component also contributes to the impairment.

Structural, Microstructural, and Metabolic Alterations in Primary Progressive Aphasia Variants

“…However, it has been shown that even early stage lv-PPA patients have subtle semantic disorders when tested with psycholinguistic paradigms ( 64 ), which is coherent with our imaging findings revealing the involvement of anterior portions of the temporal lobe contributing to semantics. Likewise, sv-PPA patients have, in addition to semantic breakdown, lexical disorders as revealed by psycholinguistic testing ( 64 , 65 ), which is coherent with our imaging findings revealing the involvement of posterior portions of the temporal lobe implementing the mental lexicon.…”

The relationship between response consistency in picture naming and storage impairment in people with semantic variant primary progressive aphasia.

“…In this case, semantic representations themselves are intact but cannot be accessed reliably. This may occur in the early stages of svPPA, in which comprehension is still relatively intact but individuals appear to have reduced naming abilities because of weakened access to semantic representations in language production (Mesulam et al, 2009; Wilson, Dehollain, Ferrieux, Christensen, & Teichmann, 2017).…”

“…In this case, semantic representations themselves are intact but cannot be accessed reliably. This may occur in the early stages of svPPA, in which comprehension is still relatively intact but individuals appear to have reduced naming abilities because of weakened access to semantic representations in language production (Mesulam et al, 2009;Wilson, Dehollain, Ferrieux, Christensen, & Teichmann, 2017). Warrington and Shallice (1979) proposed that one of the main characteristics that can be used to distinguish between a storage deficit and an access deficit is response consistency.…”

The relationship between response consistency in picture naming and storage impairment in people with semantic variant Primary Progressive Aphasia

“…In this case, semantic representations themselves are intact but cannot be accessed reliably. This may occur in the early stages of svPPA, where comprehension is still relatively intact but individuals appear to have reduced naming abilities due to weakened access to semantic representations in language production (Mesulam et al, 2009;Wilson, Dehollain, Ferrieux, Christensen, & Teichmann, 2017). Warrington and Shallice (1979) proposed that one of the main characteristics that can be used to distinguish between a storage deficit and an access deficit is response consistency.…”