A thesis submitted in partial fulfilment of - Queen Margaret University

(as in semantic dementia) as well as difficulties accessing representations
stored in the semantic system (word-finding errors from people with aphasia). As
with the lexicon there has also been much discussion about how many semantic
systems there are. The interpretation of the presentation of semantic categoryspecific
deficits in some people with brain damage is controversial (Caramazza,
1998). Studies have reported dissociations, in particular between animate and
inanimate objects (Warrington and Shallice, 1984; Silveri and Gainotti, 1988)
and living and non-living things (Warrington and McCarthy, 1983; Hillis and
Caramazza, 1991). There are those who advocate the unimodal semantic
system (for example, Caramazza, Hillis, Rapp and Romani, 1990; Hillis, Rapp,
Romani, and Caramazza, 1990) where there is one central store of meaning that
can be accessed by all modalities. Others advocate multiple semantic systems
as evidenced by category-specific semantic disorders. However Capitani,
Laiacona, Mahon and Caramazza (2003) reviewed evidence in favour of
category-specific deficits and reported that the existence of reliable cases which
could indicate multi-semantic systems was not very strong.
2.8.3 Grammatical behaviour of words
Inherent in words are different grammatical markers, which indicate how a word
should be used within a given sentence – nouns (words for objects), proper
nouns (words naming people or places), verbs (words describing actions) and
function words (for example, he, she, the). Although not universally accepted,
category-specific deficits have also been described for grammatical classes of
words such as verbs and nouns (Daniele et al., 1994). Some investigations have
suggested that they are dissociated anatomically (Daniele et al., 1994) and
functionally as people with aphasia often have more difficulty retrieving verbs
than nouns (Breedin, Saffran, and Schwartz, 1998; Caramazza and Hillis, 1991)
suggesting that these word classes behave differently. Warburton, Wise, Price,
Weiller, Hadar and Ramsay (1996) also found dissociations between verbs and
nouns with healthy people from PET scans. However, no differences in neural
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