Orolaryngeal reflex responses to changes in affective state

Previous research has shown that the eye-blink startle reflex can be modulated by changes in affective state. The purpose of the present study was to determine whether human perioral and trigemino-laryngeal reflexes are sensitive to affective state changes. Impetus for this study comes from theories suggesting that orolaryngeal reflexes may be modulated by affective states, and as such influence voice and speech production. Subjects were 24 classically trained female sopranos (21-35 years). Each produced a pursing lip posture while sustaining the continuant /m/ at 440 Hz and at a comfortable voice intensity level. Simultaneously subjects were shown an aversive, pleasant, or neutral slide (experimental conditions) or no slide (control condition) and received unanticipated, servo controlled mechanical taps to the midline upper lip. Perioral responses were recorded bilaterally from the orbicularis oris inferior (OOI) muscle using surface electromyography (EMG). Trigemino-laryngeal responses were obtained indirectly by measuring changes in the voltage analog of the voice fundamental frequency (VF(o)). Reflex responses were detected by smoothing and signal-averaging the VF(o) and rectified EMG signals. Response magnitude and latency measures were compared across the affective valence and no-slide conditions. Statistically significant differences were not observed between conditions for the magnitude or temporal measures of either reflex. Significant differences, independent of affective valence, were observed between right and left early excitatory perioral response magnitudes. Differences between the startle and orolaryngeal reflexes, as well as the implications of these findings for speech motor control, are discussed.