Novel primitive swallowing reflex: facial receptor distribution and stimulus characteristics
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S R Orenstein1, I Bergman, R Proujansky
1Division of Pediatric Gastroenterology, University of Pittsburgh School of Medicine, Pennsylvania.
Insights
A primitive swallow reflex in infants is triggered by diffuse facial stimulation, particularly around the lips, in awake, non-crying infants. This reflex is not elicited by light touch or corneal stimulation.
Area of Science:
- Neonatal physiology
- Developmental neuroscience
- Pediatric reflexes
Background:
- A primitive swallowing reflex, triggered by air puffs to the face, was previously identified.
- The afferent pathways, stimulus characteristics, and behavioral prerequisites for this reflex remain unclear.
Purpose of the Study:
- To determine the facial afferent distribution for the primitive swallow reflex.
- To identify stimulus characteristics necessary for eliciting the reflex.
- To investigate the role of infant's antecedent behavior in this reflex.
Main Methods:
- Clinical observation of swallowing in response to facial stimulation in nine infants.
- Manometric documentation of swallowing in four infants.
- Systematic stimulation of various facial areas, including lips and perioral regions.
Main Results:
- Consistent positive responses to stimulation of the maxillary-ophthalmic and maxillary-mandibular areas.
- Stimulation of lips (including perioral areas) yielded significantly more positive swallow responses (59%) compared to non-lip facial areas (25%).
- The reflex was not elicited by light touch, including corneal stimulation, and was incompatible with crying or sleep.
Conclusions:
- The primitive swallow reflex requires diffuse stimulation, potentially thermal, to the perioral facial area.
- The infant must be awake and not crying for the reflex to occur.
- This reflex is distinct from tactile-elicited swallows and highlights the importance of perioral sensory input in neonatal feeding behaviors.
Abstract:
We recently described a primitive swallowing reflex: swallowing as a response to a puff of air administered to the face. To identify the facial afferent distribution of this response, the necessary characteristics of the stimulus, and the role of the infant's antecedent behavior, we studied 13 infants who had demonstrated this reflex. We evaluated nine infants by clinically observing for swallowing in response to a total of 135 stimulus applications. All nine had consistently positive responses to the maxillary-ophthalmic area and to the maxillary-mandibular area. Two had consistent responses to stimulation of the mandibular area alone; these were positive. Six had consistent responses to stimulation of the ophthalmic area alone; these were negative. Four infants, evaluated by manometric documentation of swallowing (a total of 137 stimulus applications) demonstrated 47 of 79 (59%) positive responses to stimuli applied to facial areas including any parts of the lips, but only 7 of 28 (25%) positive responses to stimuli applied to facial areas excluding all parts of the lips (chi-square P = 0.002). Light touch to any facial area, including the cornea, failed to produce a swallow in any infant. Crying and sleep were incompatible with the reflex. This newly identified primitive swallow reflex seems to require diffuse stimulation, possibly thermal, to the perioral area of the face in an awake and noncrying infant.