Some Observations of Articulation during Labial Sensory Deprivation

Photographic measurement techniques were used to study labial movement under normal speaking conditions and when sensory feedback from the lips was reduced by trigeminal nerve-block anesthesia. Lip activity was photographed as a subject spoke monosyllabic words initiated by /p/, /b/, or /m/. Qualitative observations were made of general articulatory characteristics, and frame-by-frame quantitative analyses were performed on the release phase of each bilabial consonant. The labial sensory deprivation condition resulted primarily in phonetic articulatory changes due to an overall reduction in the normal rate, accuracy, and extent of lip movement. The data were discussed in terms of the differential effects of reduced labial sensory feedback on the bilabial consonants and interpreted with respect to open- and closed-loop control of articulation.