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Abstract:
We compared comprehension on a resource-demanding task to
comprehension on a minimal-demanding word-detection procedure in
Parkinsons disease (PD). Subjects detected target words within
sentences. Half contained phonetic errors, in either grammatical or
content words, and sentences were grammatically simple or contained
a center-embedded clause that was subject-relative or
object-relative. The target word was immediately after or four
syllables after the phonetic error. In the resource-demanding
assessment, subjects answered probes about 24 sentences featuring
subject-gap or object-gap center-embedded subordinate clauses. We
also assessed executive resources with clinical measures. PD
patients were insensitive to errors in grammatical words,
regardless of clausal structure. PD patients were sensitive to
content word errors in object-relative sentences when separated by
four syllables from the target word [t(18)=2.77; p<0.05],
indicating sensitivity to content word errors within a delayed time
window. For the resource-demanding task, PD patients were less
accurate answering probes of sentences containing object-relative
center-embedded clauses [t(18)=3.46; p<0.005]. Delayed
sensitivity to content words in object-relative sentences
correlated with time to complete Trails B and
Category-naming-fluency. Comprehension accuracy on the traditional
measure correlated with Digit-span-backward [r(17)=0.51; p<0.05]
and Category-naming-fluency [r(17)=0.48; p<0.05]. PD patients
lack of sensitivity to grammatical words and delayed sensitivity to
content words, as well as the correlations with executive measures,
supports the hypothesis that specific executive resource
limitations contribute to sentence comprehension difficulty in
PD.
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