Anatomy and Neuroscience - Research Publications
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ItemAcoustic analysis of the effects of 24 hours of sustained wakefulnessVogel, AP ; Fletcher, J ; Maruff, P (Australasian Speech Science and Technology Association, 2010)The effect of 24 hours of sustained wakefulness on the speech of healthy adults is poorly documented. Therefore, speech samples were systematically acquired (e.g., every four hours) from 18 healthy adults over 24 hours. Stimuli included automated and extemporaneous tasks, sustained vowel and a read passage. Measures of timing and frequency were derived acoustically using Praat and significant changes were observed on all tasks. The effect of fatigue on speech was found to be strongest just before dawn (after 22 hours). Key features of timing (e.g., mean pause length), frequency (e.g., F4 variation) and power (alpha ratio) changed as a function of increasing levels of fatigue. Index Terms: fatigue, voice, tiredness, clinical marker
ItemNo Preview AvailableAcoustic analysis of the effects of sustained wakefulness on speechVogel, AP ; Fletcher, J ; Maruff, P (ACOUSTICAL SOC AMER AMER INST PHYSICS, 2010-12-01)Exposing healthy adults to extended periods of wakefulness is known to induce changes in psychomotor functioning [Maruff et al. (2005). J. Sleep Res. 14, 21-27]. The effect of fatigue on speech is less well understood. To date, no studies have examined the pitch and timing of neurologically healthy individuals over 24 h of sustained wakefulness. Therefore, speech samples were systematically acquired (e.g., every 4 h) from 18 healthy adults over 24 h. Stimuli included automated and extemporaneous speech tasks, sustained vowel, and a read passage. Measures of timing, frequency and spectral energy were derived acoustically using PRAAT and significant changes were observed on all tasks. The effect of fatigue on speech was found to be strongest just before dawn (after 22 h). Specifically, total speech time, mean pause length, and total signal time all increased as a function of increasing levels of fatigue on the reading tasks; percentage pause and mean pause length decreased on the counting task; F4 variation decreased on the sustained vowel tasks /a:/; and alpha ratio increased on the extemporaneous speech tasks. These findings suggest that acoustic methodologies provide objective data on central nervous system functioning and that changes in speech production occur in healthy adults after just 24 h of sustained wakefulness.
ItemNo Preview AvailableReliability, stability, and sensitivity to change and impairment in acoustic measures of timing and frequencyVogel, AP ; Fletcher, J ; Snyder, PJ ; Fredrickson, A ; Maruff, P ; Dale, R ; Burnham, D ; Stevens, C (Elsevier Inc., 2011)Assessment of the voice for supporting classifications of central nervous system (CNS) impairment requires a different practical, methodological, and statistical framework compared with assessment of the voice to guide decisions about change in the CNS. In experimental terms, an understanding of the stability and sensitivity to change of an assessment protocol is required to guide decisions about CNS change. Five experiments (N=70) were conducted using a set of commonly used stimuli (eg, sustained vowel, reading, extemporaneous speech) and easily acquired measures (eg, f0–f4, percent pause). Stability of these measures was examined through their repeated application in healthy adults over brief and intermediate retest intervals (ie, 30 seconds, 2 hours, and 1 week). Those measures found to be stable were then challenged using an experimental model that reliably changes voice acoustic properties (ie, the Lombard effect). Finally, adults with an established CNS-related motor speech disorder (dysarthria) were compared with healthy controls. Of the 61 acoustic variables studied, 36 showed good stability over all three stability experiments (eg, number of pauses, total speech time, speech rate, f0–f4). Of the measures with good stability, a number of frequency measures showed a change in response to increased vocal effort resulting from the Lombard effect challenge. Furthermore, several timing measures significantly separated the control and motor speech impairment groups. Measures with high levels of stability within healthy adults, and those that show sensitivity to change and impairment may prove effective for monitoring changes in CNS functioning.
ItemNo Preview AvailableThe impact of task automaticity on speech in noiseVogel, AV ; Fletcher, J ; Maruff, PT (Elsevier Science, 2014)In the control of skeleto-motor movement, it is well established that the less complex, or more automatic a motor task is, the less variability and uncertainty there is in its performance. It was hypothesized that a similar relationship exists for integrated cognitive-motor tasks such as speech where the uncertainty with which actions are initiated may increase when the feedback loop is interrupted or dampened. To investigate this, the Lombard effect was exploited to explore the acoustic impact of background noise on speech during tasks increasing in automaticity. Fifteen healthy adults produced five speech tasks bearing different levels of automaticity (e.g., counting, reading, unprepared monologue) during habitual and altered auditory feedback conditions (Lombard effect). Data suggest that speech tasks relatively free of meaning or phonetic complexity are influenced to a lesser degree by a compromised auditory feedback than more complex paradigms (e.g., contemporaneous speech) on measures of timing. These findings inform understanding of the relative contribution speech task selection plays in measures of speech. Data also aid in understanding the relationship between task automaticity and altered speech production in neurological conditions where dual impairments of movement and cognition are observed (e.g., Huntington’s disease, progressive aphasia).