Hypophonia and dysarthria sometimes characterize speech in patients with PD. As compared to patients with AD, aphasia and paraphasic errors are rarely observed in PD, although production and comprehension of complex syntax may be reduced on occasion (43-45). Comprehension of written material and writing (limited by motor impairments) is also relatively preserved in PD. Visual confrontation naming tasks, requiring naming of pictured or actual objects, is preserved in PD without dementia (46), although rare studies report subtle naming impairments in early PD (47). More common are deficits on verbal fluency tasks requiring, within time constraints, the oral generation of words belonging to semantic categories or beginning with certain letters of the alphabet (46,48). Verbal fluency decrements are not universally observed in PD, but, when present, probably reflect deficient use of word retrieval strategies such as clustering and/or switching (48), meaning grouping of words by component sound or category, and moving efficiently between sounds and categories.
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