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Abstract:
Abstract: Parkinsonis disease (PD) patients have sentence
comprehension difficulty. This may be due to a grammatical
impairment or a limitation in executive resources that contribute
to comprehension. We addressed these competing hypotheses by
assessing PD patients and healthy controls with on- and off-line
sentence comprehension measures. The on-line task asked subjects to
detect a target word in an aural sentence. Unbeknownst to subjects,
the target at times followed an incorrect grammatical agreement.
Both controls (mean +/-S.D.=105.7 +/-98.3 msec) and PD patients
(mean +/-S.D.=170.2 +/-199.8 msec) took significantly longer (at
least p<0.001) to respond to a target when it immediately
followed an agreement violation compared to a coherent agreement,
demonstrating sensitivity to agreements in their immediate temporal
window. This difference was not evident in either group when the
target followed the violation by four syllables. The off-line task
asked subjects to answer active- or passive-voice questions probing
semantically unconstrained aural sentences with a subject- or
object-relative subordinate clause either terminally-located or
center-embedded. PD patients were impaired in off-line
comprehension (mean +/-S.D. overall accuracy=50.3% +/-12.3%
correct). They were most impaired at understanding object-relative
center-embedded sentences. Performance on executive measures also
was impaired and this correlated with off-line comprehension.
On-line sensitivity to grammatical agreements suggests that PD
patients have preserved grammatical comprehension, but an executive
limitation interferes with their off-line comprehension.
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