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Abstract:
In recent years, studies have shown that the production
impairment in agrammatic aphasia is more selective than we used to
think, and that agrammatism can no longer be described as a
complete loss of syntax. This study investigated the nature and
extent of the syntactic deficit in agrammatic production, focusing
on three domains: verb inflections, subordinations, and
interrogatives.
Twelve Hebrew speaking and two Palestinian Arabic speaking
agrammatic patients participated in the study. Tasks included
elicitation, sentence completion and sentence repetition tasks. In
addition, the spontaneous speech of these patients containing 2272
utterances was analyzed, as well as speech corpora in several other
languages.
The results show an intricate pattern of dissociations within
and between languages. A sharp dissociation was revealed in Hebrew
and Arabic between tense and agreement inflections. While tense is
impaired (41% errors in completion task), agreement is almost
intact (4% errors). A selective impairment was also found in the
production of subordinations and questions. Agrammatics encounter
severe difficulties producing tensed embedded sentences, but they
retain the ability to produce other types of embeddings, such as
small clauses and reduced relatives (in Hebrew, English, and
French). In question production in Hebrew and Arabic, Wh questions
are impaired, but yes/no questions are preserved. This dissociation
was not found in English, where both Wh- and yes/no-questions are
impaired.
A selective syntactic account, the Tree Pruning Hypothesis, is
proposed for the findings (TPH, Friedmann, 1994; Friedmann &
Grodzinsky, 1997; 1999). The TPH adopts Pollocks (1989) Split
Inflection hypothesis, according to which tense and agreement are
represented in separate nodes in the syntactic tree, and his
phrasal nodes order CP>TP>AGRP>VP. Using this linguistic
tool, the TPH accounts for the fine pattern of dissociations in
terms of a deficit in syntactic tree building. According to the
TPH, agrammatic aphasics are unable to construct the tree up to its
highest nodes. Thus, structures that depend on the high nodes, CP
and TP, are impaired, but structures that require only lower nodes
(AgrP, VP) are intact. The pattern of impairment follows: Tense
node is impaired, but Agreement node, which is located lower in the
tree, is intact, and therefore tense inflection (as well as copulas
and subject pronouns) is impaired, but agreement inflection is
intact. Because the CP is impaired, agrammatics cannot produce Wh
questions and embeddings that require the CP, but can construct
questions and embedded clauses which do not require CP such as
yes/no questions in Hebrew and Arabic, small clauses and reduced
relatives. The pruning of the tree explains the cross-linguistic
dissociation as well: since yes/no questions involve elements in CP
in English but not in Hebrew and Arabic, they are impaired in
English, but not in Hebrew and Arabic.
To conclude, current syntactic theory provides tools to
characterize in greater accuracy the nature of the agrammatic
impairment in production, and to account for dissociations within
and between languages. Deficits that have been regarded as
unrelated until now appear to be closely related: the agrammatic
deficits in inflection, subordination, and question production, are
all part and parcel of the same impairment - the pruning of the
syntactic tree.
Friedmann, N. 1994. Morphology in agrammatism: A dissociation
between tense and agreement. M.A. thesis. Tel Aviv University.
Friedmann, N., & Grodzinsky, Y. 1997. Tense and agreement in
agrammatic production: pruning the syntactic tree. Brain and
Language, 56, 397-425.
Friedmann, N., & Grodzinsky, Y. 1999. Split inflection in
neurolinguistics. In L. Rizzi and M.-A. Friedemann (Eds.) The
Acquisition of Syntax: Studies in comparative developmental
linguistics. Longman Linguistics Library Series. Geneva:
Switzerland.
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