Speech errors in progressive non-fluent aphasia

Abstract

The nature and frequency of speech production errors in neurodegenerative disease have not previously been precisely quantified. In the present study, 16 patients with a progressive form of nonfluent aphasia (PNFA) were asked to tell a story from a wordless children's picture book. Errors in production were classified as either phonemic, involving language-based deformations that nevertheless result in possible sequences of English speech segments; or phonetic, involving a motor planning deficit and resulting in non-English speech segments. The distribution of cortical atrophy as revealed by structural MRI scans was examined quantitatively in a subset of PNFA patients (N=7). The few errors made by healthy seniors were only phonemic in type. PNFA patients made more than four times as many errors as controls. This included both phonemic and phonetic errors, with a preponderance of errors (82%) classified as phonemic. The majority of phonemic errors were substitutions that shared most distinctive features with the target phoneme. The systematic nature of these substitutions is not consistent with a motor planning deficit. Cortical atrophy was found in prefrontal regions bilaterally and peri-Sylvian regions of the left hemisphere. We conclude that the speech errors produced by PNFA patients are mainly errors at the phonemic level of language processing and are not caused by a motor planning impairment.

Why are patients with progressive nonfluent aphasia nonfluent?

“…While some observations have associated speech-sound errors with a disorder of motor-speech planning known as AOS, 3,7 our quantitative analyses suggest that these errors are much more often due to a linguistic disruption of the phonologic processing system. 27 Regardless of the basis for speech-sound errors in PNFA, a regression analysis in the present study revealed that reduced speech fluency is not related to speech-sound errors.…”

Criteria for the diagnosis of corticobasal degeneration

“…13,15,36 Apraxia of speech (AOS) has also been described in CBD on its own and coexisting with aphasia, 20,32 though challenges in diagnosing AOS limit efforts to estimate its frequency. Some consider AOS a speech disorder rather than language dysfunction 37 ; consensus has been elusive. Speech abnormalities in general were described in 53% of cases (23% at presentation) (table 3).…”

Phonological simplifications, apraxia of speech and the interaction between phonological and phonetic processing

“…Consistent with our findings, Shattuck-Hufnagel and Klatt (1979) reported no tendency to simplify in the speech errors of adult controls with fluent speech. Also Ash et al (2010) found no markedness effects in patients with progressive aphasia that they described as non-fluent, but who showed no evidence of articulatory difficulties (e.g., few phonetic errors, high rates of vowel errors).…”

“…Slurred phonemes: A stretch of speech or a whole word produced in a slurred fashion; systematically slurred speech is associated with dysarthria (e.g., Duffy et al, 2007), but stretches of slurred speech also occur in patients with AoS; 2. Distorted phonemes: Included in this category are lenitionswell-formed phonemes produced with less articulatory force (e.g., see Ash et al, 2010) -and phonemes produced with a perceptible deviation from the target in place, manner or timing (see Kent and Rosenbek, 1983;Odell et al, 1990;McNeil et al, 1990); 3. An audible or, more rarely, visual effort in producing the word, generally at word beginning (for initiation difficulties see Kent and Rosenbek, 1983;Strand and McNeil, 1996; for effortful trial and error and groping, see McNeil et al, 1990McNeil et al, , 2009Odell et al, 1990).…”