Electrophysiological Evidence of Early Cortical Sensitivity to Human Conspecific Mimic Voice as a Distinct Category of Natural Sound.

Purpose From an anthropological perspective of hominin communication, the human auditory system likely evolved to enable special sensitivity to sounds produced by the vocal tracts of human conspecifics whether attended or passively heard. While numerous electrophysiological studies have used stereotypical human-produced verbal (speech voice and singing voice) and nonverbal vocalizations to identify human voice-sensitive responses, controversy remains as to when (and where) processing of acoustic signal attributes characteristic of "human voiceness" per se initiate in the brain. Method To explore this, we used animal vocalizations and human-mimicked versions of those calls ("mimic voice") to examine late auditory evoked potential responses in humans. Results Here, we revealed an N1b component (96-120 ms poststimulus) during a nonattending listening condition showing significantly greater magnitude in response to mimics, beginning as early as primary auditory cortices, preceding the time window reported in previous studies that revealed species-specific vocalization processing initiating in the range of 147-219 ms. During a sound discrimination task, a P600 (500-700 ms poststimulus) component showed specificity for accurate discrimination of human mimic voice. Distinct acoustic signal attributes and features of the stimuli were used in a classifier model, which could distinguish most human from animal voice comparably to behavioral data-though none of these single features could adequately distinguish human voiceness. Conclusions These results provide novel ideas for algorithms used in neuromimetic hearing aids, as well as direct electrophysiological support for a neurocognitive model of natural sound processing that informs both neurodevelopmental and anthropological models regarding the establishment of auditory communication systems in humans. Supplemental Material https://doi.org/10.23641/asha.12903839.

Gender identification from high-pass filtered vowel segments: the use of high-frequency energy.

The purpose of this study was to examine the use of high-frequency information for making gender identity judgments from high-pass filtered vowel segments produced by adult speakers. Specifically, the effect of removing lower-frequency spectral detail (i.e., F3 and below) from vowel segments via high-pass filtering was evaluated. Thirty listeners (ages 18-35) with normal hearing participated in the experiment. A within-subjects design was used to measure gender identification for six 250-ms vowel segments (/æ/, /ɪ /, /ɝ/, /ʌ/, /ɔ/, and /u/), produced by ten male and ten female speakers. The results of this experiment demonstrated that despite the removal of low-frequency spectral detail, the listeners were accurate in identifying speaker gender from the vowel segments, and did so with performance significantly above chance. The removal of low-frequency spectral detail reduced gender identification by approximately 16 % relative to unfiltered vowel segments. Classification results using linear discriminant function analyses followed the perceptual data, using spectral and temporal representations derived from the high-pass filtered segments. Cumulatively, these findings indicate that normal-hearing listeners are able to make accurate perceptual judgments regarding speaker gender from vowel segments with low-frequency spectral detail removed via high-pass filtering. Therefore, it is reasonable to suggest the presence of perceptual cues related to gender identity in the high-frequency region of naturally produced vowel signals. Implications of these findings and possible mechanisms for performing the gender identification task from high-pass filtered stimuli are discussed.

The application of evidence-based practice to nonspeech oral motor treatments.

PURPOSE: The purpose of this article is to help speech-language pathologists (SLPs) apply the principles of evidence-based practice (EBP) to nonspeech oral motor treatments (NSOMTs) in order to make valid, evidence-based decisions about NSOMTs and thus determine if they are viable treatment approaches for the management of communication disorders. METHOD: A detailed description of EBP is provided, including levels of evidence for rating the quality of evidence. NSOMTs are described and a survey of the literature on NSOMTs is provided along with a determination of the level of evidence of each study reported. A systematic literature search was conducted using the electronic databases of MEDLINE and CINAHL (Cumulative Index to Nursing and Allied Health Literature) within an unrestricted time period. In addition, reference lists from identified articles were also reviewed. Ethical and fiscal issues related to EBP and NSOMTs, as well as clinical implications of EBP for the use of NSOMTs, are discussed. RESULTS: A total of 45 articles/reports were published between 1981 and 2006 in peer-reviewed and non-peer-reviewed journals. Most of the sources (25) relied on weak anecdotal evidence and opinions. Moreover, studies that employed stronger designs reported negative results for NSOMTs (i.e., evidence against the use of NSOMTs for modifying speech). CONCLUSION: Despite their use for many years and their popularity among some SLPs for the treatment of a wide variety of speech problems in children and adults, NSOMTs are controversial because sufficient evidence does not exist to support their effectiveness in improving speech. Moreover, limited evidence exists for the use of NSOMTs to facilitate nonspeech activities. Therefore, the available evidence does not support the continued use of NSOMTs as a standard treatment and they should be excluded from use as a mainstream treatment until there are further data. SLPs should consider the principles of EBP in making decisions about NSOMTs.

Academic and clinical training in cleft palate for speech-language pathologists.

OBJECTIVE: The purpose of this study was to obtain information about academic and clinical training of speech-language pathology students in cleft palate (CP). METHODS: Representatives of 232 accredited graduate programs in speech-language pathology were invited via e-mail to complete a web-based 32-item questionnaire. Questions focused on the type and nature of courses offered related to CP, availability of clinical practica, and number of hours of clinical experience by students. An item-by-item analysis was conducted and descriptive statistics obtained. RESULTS: A total of 127 (54.7%) of the programs responded. Sixty-seven percent offered coursework exclusively devoted to CP, and for 53% of these it was a required course. For the programs that did not offer an exclusive course on CP, 35% indicated that CP was covered in other courses such as articulation, voice, or anatomy and physiology. Fifty-four percent of the programs offered clinical practica in CP. For these, a median of five students of a median graduate speech-language pathology class of 43 were enrolled in practica involving CP (range = 0-21), and students spent a median of 2 hours in practica involving CP (range = 0-100). CONCLUSIONS: Cleft palate is a complex disorder to which many students have limited exposure and for which more graduate training is unlikely since the 1993 American Speech-Language-Hearing Association (ASHA) certification changes. As a result, there is a need to look towards alternative methods to enhance the educational and clinical experiences of students and practitioners in cleft palate.