Phonological encoding in apraxia of speech and aphasia

Abstract

Background: Apraxia of speech (AOS) is considered a speech motor planning/programming disorder. While it is possible that co-occurring phonological impairments exist, the speech motor planning/programming deficit often makes it difficult to assess the phonological encoding stage directly. Studies using online methods have suggested that activation of phonological information may be protracted in AOS. Aims: The present study was designed to investigate the integrity of the phonological encoding stage in AOS and aphasia. We tested two specific hypotheses, the Frame Hypothesis and the Segment Hypothesis. According to the Frame Hypothesis, speakers with AOS have an impairment in retrieving metrical frames (e.g., number of syllables); according to the Segment Hypothesis, speakers with AOS have an impairment in retrieving segments (e.g., consonants). Methods & Procedures: Four individuals with AOS and varying degrees of aphasia, two speakers with aphasia, and 13 age-matched control speakers completed an online priming task in which participants name pictures in sets that do or do not share number of syllables (e.g., balcony-coconut-signature vs. balcony-carrot-sock), the initial consonant (e.g., carpenter-castle-cage vs. carpenter-beaver-sun), or both (e.g., boomerang-butterflybicycle vs. boomerang-sausage-cat). Error rates and reaction times were measured. Outcomes & Results: Data for controls replicated previous literature. Reaction time data supported the Segment Hypothesis for speakers with AOS and for one speaker with aphasia without AOS, with no differences in pattern from controls for the other speaker with aphasia without AOS. Conclusions: These results suggest that speakers with AOS may also have difficulties at the phonological encoding stage. Theoretical and clinical implications of these findings are discussed.

Identification and Remediation of Phonological and Motor Errors in Acquired Sound Production Impairment

“…Although our work has covered a relatively small number of participants to date, it suggests that the population of those who have AOS with aphasia may include individuals who make sound deletion errors that arise in phonological processing, and that the presence of these errors may be related to whether these individuals benefit from a basic repetition training. One approach to AOS research has been to compare individuals with aphasia with AOS to individuals with aphasia without AOS on tasks that tap into the motor system (Haley et al, 2013;Maas et al, 2014Maas et al, , 2015. In some cases, the data obtained in these studies are equivocal, with only some members of the AOS with aphasia population exhibiting the expected behavior (e.g., Maas et al, 2015).…”

“…The presence of "pure" AOS in the absence of other impairments is described as rare (McNeil et al, 2009). Therefore, a number of investigations of speakers with AOS with concomitant aphasic impairments attempt to isolate the motor control system by using tasks that likely tap directly into this system (Haley, Jacks, & Cunningham, 2013;Maas, Gutiérrez, & Ballard, 2014;Maas, Mailend, & Guenther, 2015). A related issue is that the types of sound structure sequences that are difficult for the motor system to plan and enact (e.g., consonant clusters) are precisely those that are more complex phonologically as well.…”

Dynamic Acoustic Evidence of Nasalization as a Compensatory Mechanism for Voicing in Spanish Apraxic Speech

“…Apraxia of speech (AOS) is a motor speech disorder of neurological origin that selectively affects phonetic encoding processes [1][2][3][4] and results in distortions of the sound shape of words. Phonetic investigations of apraxic speech have yielded evidence for impaired laryngeal control, timing and coordination with supralaryngeal articulators [5].…”

Speech and nonspeech: What are we talking about?

“…If this is not speech, then a large body of research on speech motor control and its disorders must be rejected as fundamentally uninformative about speech production. The literature on behavioural and neural aspects of speech motor control has relied extensively on tasks involving production small sets of phrases or words – or nonwords – elicited through picture naming (Maas, Gutiérrez, & Ballard, 2014; Mailend & Maas, 2013; Wunderlich & Ziegler, 2011), imitation of auditory models (Aichert & Ziegler, 2004; Kim, Weismer, Kent, & Duffy, 2009; Smith & Zelaznik, 2004; Ziegler, 2002), reading (Bunton & Weismer, 1994; Tsao & Weismer, 1997), memory recall (Bohland & Guenther, 2006; Cholin et al, 2011; Deger & Ziegler, 2002; Maas, Robin, Wright, & Ballard, 2008; Sternberg et al, 1978), or rapid shadowing (Peschke, Ziegler, Kappes, & Baumgaertner, 2009). Some experimental paradigms to study speech motor control involve learning novel, non-native sound sequences (Moser et al, 2009; Segawa et al, 2015).…”