Spontaneous smiling and facial mimics in the neonate: A contribution to the functional role of paradoxical sleep during development

Objectives Sleeping newborns display facial mimics which give the impression of negative or positive affects. Smiling and frowning are the simplest and easily recognized. This study is an attempt to understand the neurophysiological meaning of these mimics and to define their connection with the functional role of REM sleep during ontogenesis. Methods Twelve healthy, full term neonates; 3 infants with brain malformations: two hydranencephalics and one with a left hemispherectomy were recorded, for a period of 3 hours during sleep, with the simultaneous use of a polygraphic and a video recording. It was determined during active sleep the frequency of smiling and frowning, their modality of occurrence their distribution within each active sleep. It was calculated for smiling their duration and laterality, their relationship with rapid eye movements and gross body movements. Results In the healthy neonates, 377 smiles and 1039 frownings were analyzed during active sleep. Spontaneous smiling is found to be similar to adult social smiling. Smiles were significantly more intensely expressed on the left side of the face ( P P Conclusion The data obtained in the healthy neonates and in the pathological infants are compared with the hypotheses of the functional role of paradoxical sleep during ontogenesis.