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. 2017 Apr 14;60(4):877-891.
doi: 10.1044/2016_JSLHR-S-15-0112.

Characterizing Articulation in Apraxic Speech Using Real-Time Magnetic Resonance Imaging

Christina Hagedorn  1 , Michael Proctor  2 , Louis Goldstein  1 , Stephen M Wilson  3 , Bruce Miller  4 , Maria Luisa Gorno-Tempini  4 , Shrikanth S Narayanan  1
Affiliations

Characterizing Articulation in Apraxic Speech Using Real-Time Magnetic Resonance Imaging

Christina Hagedorn et al. J Speech Lang Hear Res. .

Abstract

Purpose: Real-time magnetic resonance imaging (MRI) and accompanying analytical methods are shown to capture and quantify salient aspects of apraxic speech, substantiating and expanding upon evidence provided by clinical observation and acoustic and kinematic data. Analysis of apraxic speech errors within a dynamic systems framework is provided and the nature of pathomechanisms of apraxic speech discussed.

Method: One adult male speaker with apraxia of speech was imaged using real-time MRI while producing spontaneous speech, repeated naming tasks, and self-paced repetition of word pairs designed to elicit speech errors. Articulatory data were analyzed, and speech errors were detected using time series reflecting articulatory activity in regions of interest.

Results: Real-time MRI captured two types of apraxic gestural intrusion errors in a word pair repetition task. Gestural intrusion errors in nonrepetitive speech, multiple silent initiation gestures at the onset of speech, and covert (unphonated) articulation of entire monosyllabic words were also captured.

Conclusion: Real-time MRI and accompanying analytical methods capture and quantify many features of apraxic speech that have been previously observed using other modalities while offering high spatial resolution. This patient's apraxia of speech affected the ability to select only the appropriate vocal tract gestures for a target utterance, suppressing others, and to coordinate them in time.

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Figures

Figure 1.
Figure 1.
Structural brain magnetic resonance imaging showing left-lateralized atrophy in study participant. Left panel: midsagittal plane. Center: coronal plane (left hemisphere to left of image). Right: axial plane (left hemisphere to left of image).
Figure 2.
Figure 2.
Mean midsagittal magnetic resonance imaging slice showing vocal tract regions (labial, alveolar, velar) within which articulatory activity is estimated from correlated pixel intensity (details in Lammert et al., 2010).
Figure 3.
Figure 3.
Top: Acoustic waveform and time-aligned estimated constriction functions (labial, alveolar, velar) in /tɒp–kɒp/ repetition task. Bottom: magnetic resonance imaging frames showing articulatory postures for target /t/, target /k/, and first intrusion error (coproduced /t/ + /k/).
Figure 4.
Figure 4.
Acoustic waveform (top) and time-aligned estimated constriction functions (labial, alveolar, velar) in second /tɒp–kɒp/ repetition trial. Labial and tongue tip gestures coordinated in phase (synchronously; arrows). Dorsal gestures are missing at expected times.
Figure 5.
Figure 5.
Acoustic waveforms and time-aligned labial, alveolar, velar constriction functions for fluent (top) and apraxic (bottom) utterances, “(I) can type ‘bow know’ five times.” Top: Fluent utterance (25-year-old typical American male) showing high degree of gestural overlap, smooth gestural transitions, and shorter overall duration. Bottom: Constriction functions reveal unphonated tongue tip intrusion (arrow) during labial closure for /b/ in apraxic utterance.
Figure 6.
Figure 6.
Two productions by apraxic subject of initial fricative in federation. Left: Target production. Right: Labial constriction coproduced with intrusive lingual gesture corresponding to tongue posture observed during /ɹ/ production later in same word. Labiodental frication is not discernible in acoustic signal of Token 2.
Figure 7.
Figure 7.
Covert tongue tip gesture during first (silent) attempt at producing coronal-initial word know in the utterance, “I can type ‘bone know’ five times.”
Figure 8.
Figure 8.
Three silent tongue tip gestures preceding successful (vocalized) production of coronal-initial word temperatures.
Figure 9.
Figure 9.
Silent production (see attenuated acoustic signal [top], red text [bottom]) of entire sequence type know (/taɪp noʊ/) in utterance “I can (type know) know…”
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References

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