The use of reaction time measures to evaluate nonword reading in primary progressive aphasia.

We reported on a subject with nonfluent primary progressive aphasia (PPA), NL, who demonstrated an impaired ability to make rhyme judgments (Dowhaniuk, Dixon, Roy, Black, & Square, in press). Our hypothesis was that these deficits represent a precursor to phonological alexia. However, no definitive evidence supported the existence of a phonological reading impairment as NL made relatively few errors reading nonwords. To further evaluate NL's nonword reading, nonword and real word reaction times were compared. NL's reaction times were significantly longer for only nonwords compared to the slowest control subject. We then assessed the first two stages of processing involved in nonword reading (Coltheart, 1996). NL did not demonstrate deficits with graphemic parsing or phoneme assignment. His continuing problems with auditory rhyme judgments support the presence of a phonological processing deficit not specific to reading. We conclude that reaction time measures allow for the detection of subtle nonword reading deficits.