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Abstract:
Background
: Are the words and rules of language subserved by distinct
mechanisms (Pinker, 1991) or a common mechanism (Elman et al.,
1996)? Neural double dissociations strengthen the dual-mechanism
case. Lexical deficits and temporal lobe damage (in posterior
aphasia, Alzheimer's disease) lead to more trouble generating
irregular (
dug
) than regular (
looked
) past tense forms; grammatical deficits and frontal/basal-ganglia
lesions (in anterior aphasia, Parkinson's disease) yield the
opposite pattern (Ullman et al., 1997). Additional double
dissociations in aphasia have also been reported (Marslen-Wilson
& Tyler, 1997). A PET study has revealed dissociations between
regular and irregular past tense production (Jaeger et al., 1996),
but has been criticized on a number of grounds (Seidenberg &
Hoeffner, in press).
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