Phonologic processing deficits in Alzheimer's disease

Abstract

We investigated phonologic production in patients with mild to moderate Alzheimer's disease (AD) on a repetition task. AD patients produced significantly more speech errors than age-matched controls. AD patients' errors, unlike those of controls, resulted in the transformation of real words into pseudowords, occurred disproportionately in word-initial positions, and were not influenced by the phonologic environment. This pattern of errors suggests a lexical phonologic retrieval deficit in AD.

Phonological and Articulatory Impairment in Alzheimer's Disease: A Case Series

“…The differing error patterns in our data compared with that of Biassou et al (1995) may simply reflect the heterogeneity of DAT, given that the patients of Biassou et al were unselected, whereas those in our study were included because of their evident speech-production difficulties. Task demands, however, are also likely to influence the types of speech errors elicited.…”

“…In the false-start errors, only the beginning of a word was activated, whereas in the phonological paraphasias, the phonological target manifested some other disruption. Correct retrieval of word-initial information in false-start errors would appear to reflect a different type of problem to that of the patients reported by Biassou et al (1995), who were most likely to make errors on the initial sounds in words. The phonologically related errors in our study are instead consistent with a deficit in one or more of the subprocesses involved in phonological encoding (Levelt et al, 1999).…”

“…To date, however, phonological deficits across groups of patients have mainly been reported in the context of experimental sentence repetition or nonword tasks which are not typical of speech production in everyday life and/or rely heavily on immediate memory (Biassou et al, 1995;Glosser et al, 1998;Glosser et al, 1997), while data on single cases have primarily been anecdotal and brief. Furthermore, although some reports provide neuropsychological results and phonological error rates Kennedy et al, 1995) it is not clear whether there is a consistent clinical profile in DAT patients with impaired speech sound production, nor whether the speech production deficits are themselves consistent when they arise in DAT.…”

“…This would approximate impaired lemma and/or phonological form retrieval. Biassou et al (1995) also hypothesized that the phonological disruption in sentence repetition in 16 patients originated in a process approximating lemma retrieval. Others (Glosser et al, 1998;Kennedy et al, 1995) suggested that the patients in their studies showed phonological deficits, but did not invoke any specific model of phonological processing.…”

“…Despite the negative findings summarized above, therefore, it is perhaps not surprising that other evidence suggests a degree of vulnerability of articulatory and phonological processing (Hart, 1988). An abnormal rate of phonological errors has been either occasionally noted, or even specifically investigated and reported, both in spontaneous speech (Gavazzi, Luzzatti, & Spinnler, 1986;Loebel, Dager, Berg, & Hyde, 1990;Shuren, Geldmacher, & Heilman, 1993) and in more formal word and sentence production tasks (Biassou et al, 1995;Emery & Breslau, 1988;Glosser, Friedman, Kohn, Sands, & Grugan, 1998;Glosser, Kohn, Friedman, Sands, & Grugan, 1997;Obler & Albert, 1984;Price et al, 1993). Because phonological and/or articulatory disruption is characteristic of several other neurodegenerative diseases which may be contenders in the differential diag- (Cummings, Darkins, Mendez, Hill, & Benson, 1988;Gordon & Illes, 1987;Hier, Hagenlocker, & Shindler, 1985;Holland, McBurney, Moossy, & Reinmuth, 1985)], if reported speech output deficits in probable AD were infrequent, and only referred to cases lacking pathological confirmation, one might question whether such deficits were actually associated with non-Alzheimer pathology in cases which had accidentally been included in a probable AD group.…”