Table 1.
A sample of neuroimaging, neurocomputational modeling, and behavioral assessment findings in childhood apraxia of speech (CAS) consistent with the hypothesis of core precision and stability deficits in phonological representations (first 12 findings) and transcoding (last eight findings).
| Processing domain | Measurement domain | Processing deficit | Measurement | Finding | Reference |
|---|---|---|---|---|---|
| Representational | Neuroimaging modalities | Auditory perceptual processes | Cortical thickness maps, including regions of interest that subserve auditory perceptual processes | 11 children with idiopathic apraxia had significantly thicker left posterior supramarginal gyri than controls. After speech treatment, 8 of 9 children with CAS had significant thinning in the posterior superior temporal gyrus compared to 1 of 3 controls. | Kadis et al. (2013) |
| Phonological representations | Electroencephalograph; mismatched negativity | 5 children with CAS were inferred to have overspecified underlying phonological representations. | Froud and Khamis-Dakwar (2012) | ||
| Phonological retrieval and syllabification | Electroencephalograph; event-related potentials | 8 children with CAS differed from controls on neurophysiological findings supporting a phonological deficit, particularly in constructing complex phonological word forms. | Preston et al. (2014) | ||
| Neurocomputational modeling | Auditory and somatosensory feedforward control | Simulation of auditory processing and motor programming deficits | Findings were interpreted as support for the hypothesis that CAS includes both underspecified representations and motor programming deficits. | Terband et al. (2014) | |
| Behavioral assessment | Auditory perceptual processes | Resynthesized and synthesized monosyllabic word tasks differing in place of articulation of the initial voiced stop consonant | 17 children with CAS had lower identification and discrimination performance than controls. | Groenen et al. (1996) | |
| Auditory perceptual processes | Resynthesized vowel continual tasks | 11 children with CAS had poorer identification and discrimination performance than controls, supporting subtle (subclinical) auditory processing deficits. | Maassen et al. (2003) | ||
| Phonological awareness | Phonological awareness tasks | 12 children with CAS had lower phonological awareness scores than children with typical speech development and children with inconsistent speech disorder. | McNeill et al. (2009) | ||
| Phonological representations | Spontaneous and forced choice rhyming tasks | 4 children with CAS had a severe rhyming deficit compared to children with typical speech development. | Marion et al. (1993) | ||
| Phonological encoding and memory | Encoding and memory subscales of a nonsense syllable repetition task | 40 participants with CAS had significantly lower encoding and memory scores than children with typical speech development and children with speech delay. | Shriberg et al. (2012) | ||
| Representations of syllables | Tasks requiring participants to identify the number of syllables in words, judge intrasyllabic sound positions, and construct syllable shapes within monosyllabic frames | 3 children with CAS had lower scores than typically speaking children on three tasks that assessed ability to perceive and access representations of syllables. | Marquardt et al. (2002) | ||
| Sequencing speech and nonverbal sequential functions | Tasks requiring participants to complete simple and complex sensorimotor and sequential memory functions on two occasions within 15 months | 17 children with CAS had lower scores on the sequential memory and complex sensorimotor tasks than typically developing children, with significant correlations between their cognitive scores and their speech impairment. | Nijland et al. (2015) | ||
| Feedforward/feedback | Conversational speech samples | 19 children with CAS did not have evident articulatory struggle (groping) and did not attempt to correct their speech errors, interpreted as support for deficits in underlying linguistic representations. | Shriberg et al. (1997) | ||
| Transcoding | Neuroimaging modalities | Planning/programming | Electroencephalograph; event-related potentials | 8 children with CAS had different electrophysiological activity than controls over the right hemisphere in the later stages of speech preparation. | Preston et al. (2014) |
| Neurocomputational modeling | Auditory and somatosensory feedforward control | Simulation of auditory processing and motor programming deficits | Findings interpreted as support for hypothesis that CAS includes both underspecified representations and motor programming deficits. | Terband et al. (2014) | |
| Behavioral assessment | Planning/programming; coordination of syllabic gestures | Acoustic analyses | 19 children with CAS had more variable and deviant coarticulation patterns between and within syllables than controls, interpreted as support for delays in coordination of syllabic gestures. | Maassen et al. (1997) | |
| Planning/programming; coarticulatory cohesion | Acoustic analyses; F2 ratios | 9 children with CAS had more variable intra- and intersyllabic anticipatory coarticulation than typically speaking children and adult women. | Nijland et al. (2002) | ||
| Planning/programming | Transcription and acoustic analyses of vowels and diphthongs produced in monosyllabic and multisyllabic real words and pseudowords | 3 children with CAS had comparable error percentages and imprecision in real and pseudowords, consistent with a motor speech deficit at the stage of planning/programming. | Blech et al. (2007) | ||
| Planning/programming; movement variability | Kinematics; motion capture system | 11 children with CAS had significantly higher movement variability than children with typical speech development and children with SD. | Grigos et al. (2015) | ||
| Planning/programming and/or feedforward/processes | Encoding and memory subscales of a nonsense syllable repetition task | 40 participants with CAS had a significantly higher percentage of addition/complication errors (e.g., on/off glides) than controls with SD. | Shriberg et al. (2012) | ||
| Feedforward processes | Auditory masking paradigm; VOT and vowel space | 9 children with CAS who produced pseudowords in masked and unmasked conditions had 1.5 times higher rates of the masking effect compared to controls with SD and typical speech. | Iuzzini-Seigel et al. (2015) |
Note. Studies focusing on feedforward/feedback processes are included in both sections, depending on the focus of the study. VOT = voice onset time; SD = speech delay.