Covariation of acoustic cues for voicing in aphasia and apraxia

We report experimental evidence on covariation between vowel onset f0 and voice onset time (VOT) in voiced and voiceless stops produced by Spanish speakers with apraxia of speech and conduction aphasia as compared to a healthy control group. These two disorders are argued to affect different components of the same dorsal stream involved in mapping sounds onto motor-based representations. On the assumption that acoustic cue covariation reflects—albeit indirectly—trade-off relationships in speech production, we explore how these deficits affect compensatory articulation. Our findings show a trade-off relationship between f0 and VOT for voiced but not voiceless stops in the control and conduction aphasia groups, and in some apraxic speakers. Interestingly, the apraxic group shows compensatory cue correlation in devoiced stops. We relate observed patterns in cue trade-off to the internal structure of phonetic categories and compensatory articulation.