After a brief introduction to the research questions and the content of the present study, Chapter 2 opens with primary information on the neurodegenerative nature of Alzheimer’s disease and its consequences. From the neuropsychological point of view, PADs suffer from memory loss, executive function impairment, aphasia, and behavioural
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and psychiatric disorders (see Spinnler 1996, for an overview). Language is affected mainly at the lexical level. Through a long and fruitful debate, authors agreed in ascribing anomia mainly to a semantic loss process and, to a lower extent, to retrieval difficulties (Chertkow et al., 1989, Chertkow & Bub, 1990; Hodges et al., 1996; Cuetos et al., 2015, a.m.o.). Anomia also affects irregular verbal morphology: PADs are impaired at retrieving verbal forms characterized by stem changes, while the use of regular morphology is spared (Colombo et al., 2009; Walenski et al., 2009). This dissociation between regular and irregular forms supports Ullman’s (2001) hypothesis of a dissociation between the declarative (mental lexicon) and the procedural (mental grammar) components of the language.
Syntax has been considered spared in PADs for a long time. Indeed, PADs are usually sensitive to syntactic violations and perform well on grammaticality judgement tasks (Kavè & Levy, 2003a; Kempler et al., 1998; MacDonald et al., 2001; Price &
Grossman, 2005). However, other studies suggest that PADs might have difficulties in the computation of syntactically complex sentences (Bickel et al., 2000; Kempler et al., 1998; Small, Kemper & Lyons, 2000; Waters, Rochon & Caplan, 1998). The number of studies that address the issue is very narrow though. In addition, experimental designs lack clear theoretical frameworks for the analysis of the experimental conditions they test.
This, combined with the presence of confounding factors (i.e., lack of minimal pairs, mix of animate and inanimate arguments, etc.), prevent authors from drawing clear conclusions, except for an observed asymmetry between simple declarative sentences and relative clauses. In the last part of the chapter, I will point out which aspects of syntactic competence deserve further investigation.
Each experimental study is preceded by an introduction to the theoretical framework in use and an overview of the main results from similar studies in different empirical fields (i.e., aphasics, children, etc.). The adoption of a theoretical framework allows for the design of precise research questions and experimental conditions. The overview of previous studies allows for comparisons across languages and across empirical fields. Both components enrich the interpretation of the collected data.
For this purpose, Chapter 3 deals with the language-specific characteristics of grammatical gender in lexical entries (Levelt, 1989 and much subsequent work) and in the process of GG retrieval (Longobardi, 1994; Friedmann & Biran, 2003). I will also
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review studies that show how vulnerable GG is in acquired linguistic disorders (Badecker et al., 1995; Luzzatti & De Bleser, 1996). The overview will help to point out which aspects are interesting for the present research.
In Chapter 4, the competence of PADs is tested with respect to GG retrieval on transparent, opaque and irregular nouns. The task takes into consideration two further factors. First, the comparison between simple and derived nouns allows for verifying how PADs deal with derivational morphology. Second, the use of experimental nouns with natural biological gender (e.g., madre, 'mother') and inanimate nouns without natural gender (e.g., cuore, 'heart') can reveal whether PADs resort to semantic information for the retrieval of GG in opaque nouns (i.e., nouns characterized by the final marker –e, which is in use both for masculine and feminine nouns).
In Chapter 5, the attention shifts to the computation of sentences characterized by movement. The chapter presents an overview of the analyses put forth for Wh-questions and Relative Clauses within the framework of Generative Grammar. As for Wh-questions, I assume that the Wh-operator is extracted from its argument position and moved to the CP layer. There, it must enter into a Spec-head relation with the verb (which is also raised to CP), in order to satisfy the Wh-Critrion (Rizzi, 1996). Similarly, Relative Clauses are derived through the extraction of an argument and movement towards the CP-layer of the RC (for a recent account see Cinque, 2008, 2014).
For both kinds of sentences, the discussion also outlines the relevant factors for the evaluation of computational abilities. For instance, the overview of Italian studies on adults (De Vincenzi, 1991, 1996), aphasic speakers (Garraffa & Grillo, 2008) and language acquisition (De Vincenzi et al., 1996; Guasti et al., 2012) reveals that the relevant factors to take into consideration for Wh-question computation are the extraction site (subject vs object Wh-questions) and the kind of Wh-element in use (Who vs WhichNP questions). Similarly, studies on RCs unveil a sharp asymmetry between subject and object RCs both in adult speakers (De Vincenzi 1991; Gordon, Hendrick &
Johnson, 2001; Traxler, Morris & Seely, 2002 among others), in aphasia (Caramazza &
Zurif, 1976; Friedmann, 2008; Garraffa & Grillo, 2008; Grillo, 2008) and in language acquisition (Contemori & Belletti, 2014; Friedmann, Belletti & Rizzi, 2009; Kidd, Brandt, Lieven & Tomasello, 2007, among many others). What is particularly interesting in RCs then is the observation of the syntactic factors that can improve the computation
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of object relatives. So far, background literature has mainly taken into consideration number and gender mismatch, lexical restriction, animacy, passive voice and resumption (Adani et al., 2010; Contemori & Belletti, 2014; Friedmann, Belletti & Rizzi, 2009, among many others). Overall, Chapter 5 sets the guidelines for the design of the experimental tasks on Wh-questions and RCs and for the interpretation of the results.
The study on Wh-question comprehension in PADs is presented in Chapter 6. PADs undergo a sentence-to-picture matching task with four experimental conditions obtained through the crossing of the two factors mentioned above (i.e., extraction site and Wh-element in use).
Chapter 7 presents results from the sentence-to-picture matching task on relative clauses. PADs listen to simple declarative sentences, subject relatives and object relatives.
The comparison among the three conditions is useful in order to verify whether PADs can deal with relative clauses (simple declaratives vs relative clauses), and whether the asymmetry between subject and object relatives increases with respect to the performance of healthy controls. The task includes three more conditions for the evaluation of factors that can reduce the complexity of ORs. For instance, I will test whether PADs benefit from passive voice, object clitic resumption and mismatch in lexical restriction for the comprehension of object relatives.
Both for Wh-questions and RCs, results will be interpreted along the lines of the account based on Relativized Minimality (Rizzi, 1990). In the vein of Friedmann, Belletti
& Rizzi (2009) and much subsequent work, I will claim that PADs are impaired at computing crossing movements between arguments in the relative clauses. In particular, the success of the derivation depends on the feature arrays of the two arguments involved.
PADs are relatively spared at computing configurations that entail relevant mismatches in features, while they are impaired at computing sentences with argument features in a configuration of inclusion.
Results from the three experimental tasks will be further summarized and discussed in Chapter 8 in order to answer the research questions addressed above.
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2 THE LINGUISTIC DEFICIT
IN PATIENTS WITH ALZHEIMER’S DISEASE
2.0 Introduction
The aim of the present chapter is to illustrate the main characteristics of dementia of the Alzheimer’s type. The first section (2.1) presents an introduction to the pathology and its symptoms in order to outline the framework in which the linguistic impairment develops.
The overview does not examine the medical causes and the neuropsychological symptoms of the disease in depth, as that would exceed the aims of a linguistic study;
however, a compendium of the main characteristics of this form of dementia (with a specific focus on what is relevant for this work) is provided.
The greater part of the chapter is devoted to an analysis of the background literature on the linguistic deficit associated to Alzheimer’s disease. The most evident and the most studied linguistic disorder in AD is anomia. Many studies have addressed the issue in the last four decades. I will summarize their main outcomes in section 2.3. A much narrower number of studies focused on the status of morphology: their (consistent) results are presented in section 2.4. Finally, section 2.5 examines studies that have previously addressed the issue of a syntactic deficit in PADs.
The overview is also instrumental in illustrating the reasons why further research on the syntactic deficit of PADs is needed. I will point out two interesting aspects of the linguistic research in AD that have already been addressed, but only partially. The first one concerns the status of syntactic information within lexical entries. The second one deals with the processing of sentences characterized by extraction movements.