The Natural Statistics of Audiovisual Speech

Humans, like other animals, are exposed to a continuous stream of signals, which are dynamic, multimodal, extended, and time varying in nature. This complex input space must be transduced and sampled by our sensory systems and transmitted to the brain where it can guide the selection of appropriate actions. To simplify this process, it's been suggested that the brain exploits statistical regularities in the stimulus space. Tests of this idea have largely been confined to unimodal signals and natural scenes. One important class of multisensory signals for which a quantitative input space characterization is unavailable is human speech. We do not understand what signals our brain has to actively piece together from an audiovisual speech stream to arrive at a percept versus what is already embedded in the signal structure of the stream itself. In essence, we do not have a clear understanding of the natural statistics of audiovisual speech. In the present study, we identified the following major statistical features of audiovisual speech. First, we observed robust correlations and close temporal correspondence between the area of the mouth opening and the acoustic envelope. Second, we found the strongest correlation between the area of the mouth opening and vocal tract resonances. Third, we observed that both area of the mouth opening and the voice envelope are temporally modulated in the 2–7 Hz frequency range. Finally, we show that the timing of mouth movements relative to the onset of the voice is consistently between 100 and 300 ms. We interpret these data in the context of recent neural theories of speech which suggest that speech communication is a reciprocally coupled, multisensory event, whereby the outputs of the signaler are matched to the neural processes of the receiver

Examining Continuity of Care for Medicaid-Enrolled Children Receiving Oral Health Services in Medical Offices

OBJECTIVE: Children living in poverty encounter barriers to dentist visits and disproportionally experience dental caries. To improve access, most state Medicaid programs reimburse pediatric primary care providers for delivering preventive oral health services. To understand continuity of oral health services for children utilizing the North Carolina (NC) Into the Mouths of Babes (IMB) preventive oral health program, we examined the time to a dentist visit after a child’s third birthday. METHODS: This retrospective cohort study used NC Medicaid claims from 2000–2006 for 95,578 Medicaid-enrolled children who received oral health services before age 3. We compared children having only dentist visits before age 3 to those with: (1) only IMB visits and (2) both IMB and dentist visits. Cox proportional hazards regression was used to estimate the time to a dentist visit following a child’s third birthday. Propensity scores with inverse-probability-of-treatment-weights were used to address confounding. RESULTS: Children with only IMB visits compared to only dentist visits before age 3 had lower rates of dentist visits after their third birthday (adjusted hazard ratio[AHR]=0.41, 95% CI=0.39 to 0.43). No difference was observed for children having both IMB and dentist visits and only dentist visits (AHR=0.99, 95% CI=0.96 to 1.03). CONCLUSIONS: Barriers to dental care remain as children age, hindering continuity of care for children receiving oral health services in medical offices