Stability, reliability, and sensitivity of acoustic measures of vowel space: A comparison of vowel space area, formant centralization ratio, and vowel articulation index.

Vowel space (VS) measurements can provide objective information on formant distribution and act as a proxy for vowel production. There are a number of proposed ways to quantify vowel production clinically, including vowel space area, formant centralization ratio, and vowel articulation index (VAI). The stability, reliability, and sensitivity of three VS measurements were investigated in two experiments. Stability was explored across three inter-recording intervals and challenged in two sensitivity conditions. Data suggest that VAI is the most stable measure across 30 s, 2 h, and 4 h inter-recording intervals. VAI appears the most sensitive metric of the three measures in conditions of fatigue and noise. These analyses highlight the need for stability and sensitivity analysis when developing and validating acoustic metrics, and underscore the potential of the VAI for vowel analysis.

Motor speech signature of behavioral variant frontotemporal dementia: Refining the phenotype.

OBJECTIVE: To provide a comprehensive description of motor speech function in behavioral variant frontotemporal dementia (bvFTD). METHODS: Forty-eight individuals (24 bvFTD and 24 age- and sex-matched healthy controls) provided speech samples. These varied in complexity and thus cognitive demand. Their language was assessed using the Progressive Aphasia Language Scale and verbal fluency tasks. Speech was analyzed perceptually to describe the nature of deficits and acoustically to quantify differences between patients with bvFTD and healthy controls. Cortical thickness and subcortical volume derived from MRI scans were correlated with speech outcomes in patients with bvFTD. RESULTS: Speech of affected individuals was significantly different from that of healthy controls. The speech signature of patients with bvFTD is characterized by a reduced rate (75%) and accuracy (65%) on alternating syllable production tasks, and prosodic deficits including reduced speech rate (45%), prolonged intervals (54%), and use of short phrases (41%). Groups differed on acoustic measures derived from the reading, unprepared monologue, and diadochokinetic tasks but not the days of the week or sustained vowel tasks. Variability of silence length was associated with cortical thickness of the inferior frontal gyrus and insula and speech rate with the precentral gyrus. CONCLUSIONS: One in 8 patients presented with moderate speech timing deficits with a further two-thirds rated as mild or subclinical. Subtle but measurable deficits in prosody are common in bvFTD and should be considered during disease management. Language function correlated with speech timing measures derived from the unprepared monologue only.