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Article Excerpt
The aim of the present study was to provide preliminary evidence of silent articulatory attempts and/or starters in AOS, and to report their effect on response latency. The kinematic properties of the silent articulatory attempts and/or starters were also investigated, as was their influence on target consonant productions. One female apraxic speaker (NR; aged 52 years; 11 years postonset left CVA) and an age-gender matched control group (n = 3; mean age = 51.33 years; SD = 2.52) were involved in the study. Electromagnetic articulography was used to record tongue movement during [TEXT NOT REPRODUCIBLE IN ASCII], [TEXT NOT REPRODUCIBLE IN ASCII], and [TEXT NOT REPRODUCIBLE IN ASCII], and their preceding silent articulatory attempts/starters, in monosyllabic words. Results indicated that silent articulatory attempts and starters were exhibited by NR, which, in part, could account for her prolonged response latencies. The movement profiles of NR's silent articulatory attempts/starters were unique, and their presence had varying effects on the target consonant productions that followed. The presence of silent articulatory attempts/starters provided additional support for a motoric account of AOS.
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Acquired apraxia of speech (AOS) typically occurs subsequent to single left-hemisphere stroke (Duffy, 2005) and is defined as "a neurologic speech disorder that reflects an impaired capacity to plan or program sensorimotor commands necessary for directing movements that result in phonetically and prosodically normal speech" (Duffy, 2005, p. 307). Clinically, persons with AOS present with sound distortions, prolonged segment (i.e., vowel or consonant) and intersegment (i.e., time between sounds, syllables, and words) durations, a slow rate of speech, and dysprosody (Duffy, 2005; McNeil, Pratt, & Fossett, 2004; McNeil, Robin, & Schmidt, 1997; Odell, McNeil, Rosenbek, & Hunter, 1990, 1991; Strand & McNeil, 1996).
Effortful, visible, and audible searching behaviors often accompany the aforementioned articulatory defects and are thought to reflect difficulties in the spatial and temporal targeting of articulatory postures (Duffy, 2005; McNeil et al., 2004; McNeil et al., 1997; Wertz, LaPointe, & Rosenbek, 1991). McNeil, Odell, Miller, and Hunter (1995) introduced the terms "attempt" and "starter" to denote two types of audible initiation difficulty. An "attempt" was defined as "any phonemic or audible nonphonemic utterance occurring prior to the final production that was separated from it by any perceived silence" (McNeil et al., 1995, p. 48), whereas a "starter" was defined as "an audible initial sound, syllable, or word characterized by a smooth transition into the final production, with no perceivable pauses or breaks" (McNeil et al., 1995, p. 48).
In their study, McNeil et al. (1995) analyzed audiotape recordings of a group of apraxic speakers (n = 4) and a group of persons with conduction aphasia (n = 4), while they repeated a set of single word stimuli three times. McNeil et al. (1995) reported 22 attempts across all trials (M = 18%; range = 0-57%) for the participants with AOS, 73% of which occurred at the sound level, and 27% of which occurred at the syllable level; nil attempts occurred at the word level. Similarly, 58% of all starters exhibited by the apraxic speakers occurred at the sound level, while the remainder occurred at the syllable level (McNeil et al., 1995). A total of 42 attempts were reported for the conduction aphasics; however, in contrast to the AOS group, only 17% of all attempts occurred at the sound level (McNeil et al., 1995). Likewise, only 14% of all starters produced by the conduction aphasics occurred at the sound level (McNeil et al., 1995). On the basis that sound level attempts are thought to indicate an underlying motor impairment, McNeil and his colleagues (1995) speculated that the initiation difficulties exhibited by the persons with AOS were consistent with a phonetic-motoric deficit, whereas the initiation difficulties experienced by the persons with conduction aphasia were consistent with a linguistic level deficit.
Prolonged response latencies, which can also be interpreted as initiation difficulty, have also been reported in persons with AOS (Deal & Darley, 1972; Varley, Whiteside, & Luff, 1999). Deal and Darley (1972) and Varley et al. (1999) reported significantly longer response latencies for their AOS groups (n = 12 and 4, respectively) in a repetition task, compared to groups of control speakers. Specifically, Deal and Darley (1972) reported an average response latency of 990 ms for the apraxic speakers and a mean response latency of 660 ms for the control group.
Having acknowledged the presence of audible initiation attempts and starters in AOS (McNeil et al., 1995), it could be speculated that silent articulatory attempts and starters precede the verbal responses of persons with AOS, which could contribute to the increased response latencies. Having relied upon audio and acoustic recordings, however, previous studies have been limited, having not had the capacity to record silent articulatory movement. For this reason, an aim of the present study was to use electromagnetic articulography (EMA) to determine if silent articulatory attempts and/or starters are exhibited by persons with AOS, and if so, what their effect on response latency is.
In addition, previous kinematic assessments of consonant production in AOS have revealed larger articulatory displacements, longer closing segment durations, and/or reductions in peak velocity (Bose, van Lieshout, & Square, 2001; McNeil & Adams, 1991; Itoh, Sasanuma, Hirose, Yoshioka, & Ushijima, 1980). Therefore, the present study also aimed to investigate the kinematic properties (i.e., maximum acceleration, deceleration, velocity, duration, and distance) of the silent articulatory attempts and/or starters in AOS. The influence of the silent articulatory attempts on the kinematic properties of proceeding target consonant productions was also investigated. Tongue-tip and tongue-back movement, in particular, were recorded, as the tongue is considered to be the most important articulator in speech production (Smith, 1992).
It was hypothesized that inaudible initiation attempts and starters would precede the apraxic speaker's utterances and would subsequently result in prolonged response latencies. In addition, it was expected that the silent initiation attempts and starters exhibited by the participant with AOS would be characterized by deviant articulatory parameters that would be relatively consistent with those of their target consonant productions. The presence of the silent articulatory attempts and starters were not expected to result in improved target consonant productions.
METHOD
Participants
A 52-year-old female participant (NR) with AOS and coexisting oral apraxia and Broca's aphasia participated in the study. NR was 11 years post-onset of left-hemisphere stroke, which occurred subsequent to a left internal carotid artery dissection that involved the deep white matter of the left fronto-parietal region.
NR exhibited a slow rate of speech characterized by prolonged intersegment durations, effortful, visible, and audible searching articulatory movements with attempts to self-correct, inconsistent errors across repetitions of the same utterance, initiation difficulties, and dysprosody. Based on these observations, and on the assessment results of the Apraxia Battery for Adults-Second Edition (ABA-2; Dabul, 2000) (Figure 1), NR was diagnosed with mild-moderate AOS and a mild oral apraxia. NR was also diagnosed with Broca's aphasia based on the assessment results of the Boston Diagnostic Aphasia Examination (BDAE; Goodglass, 2001) (Figure 2). NR had no history of a speech or neurological disorder unrelated to her stroke, nor had she undergone surgery of her lips, tongue, or jaw.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
An age (range = 49-54 years; M = 51.33 years; SD = 2.52) matched control group of three nonneurologically impaired females also participated in the study. Participants were all native English speakers and had no history of, or any form of, speech and/or neurological disorder, nor any history of oro-maxillo-facial surgery.
Assessment Procedures
In the present study, articulatory function was evaluated through the administration of a series of perceptual speech assessments, and an instrumental physiological assessment, EMA.
Perceptual Assessments
The perceptual assessment battery comprised a speech sample analysis, the Multiple Word Intelligibility Test (MWIT; Kent, Weismer, Kent, & Rosenbek, 1989), and the Frenchay Dysarthria Assessment (FDA; Enderby, 1983). For the speech sample, participants were instructed to read "The Grandfather Passage" (Darley, Aronson, & Brown, 1975) at their usual speaking rate and volume. Two speech pathologists who were unconnected to the study analyzed "The Grandfather Passage" readings according to the articulatory features (i.e., precision of consonants, length of phonemes, precision of vowels), intelligibility (i.e., overall intelligibility), and rate (i.e., general rate) sections of the perceptual rating scale described by FitzGerald, Murdoch, and Chenery (1987). Two additional items were added to the rating scale, including "word length" and "length of intersyllabic pauses" (NB: these latter features were rated according to the "length of phonemes" criteria). For the articulatory features and intelligibility sections, an equal appearing intervals scale of 1 to 4 was used, where 1 indicated normal precision/length/intelligibility pattern, 2 indicated mild disturbances, 3 indicated moderate disturbances, and 4 indicated severe disturbances. For the rate section, a...
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