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Developmental change of sucking response to taste in infants
1Department of Pediatrics, Jikei University School of Medicine, Tokyo, Japan.
Insights
Newborns exhibit primitive sucking responses to taste, which diminish over time. This taste response is likely a subcortical reflex, not a learned behavior, and decreases with age in normal infants.
Area of Science:
- Developmental Psychology
- Neuroscience
- Infant Nutrition
Background:
- Newborns' sensory responses are crucial for understanding early development.
- Sucking behavior is a primary feeding mechanism in infants.
- The neurological basis of taste perception in neonates requires further investigation.
Purpose of the Study:
- To investigate newborn responses to taste stimuli (tartrate and saline).
- To examine the developmental trajectory of taste-elicited sucking responses from birth to 5 months.
- To differentiate between subcortical and cortical influences on early sucking behavior.
Main Methods:
- Administered tartrate and saline solutions to 71 newborns (5-7 days old) during feeding.
- Recorded sucking rhythms and observed behavioral reactions via videotape analysis.
- Monitored sucking responses in 20 infants (5 with brain damage, 15 normal) monthly from birth to 5 months.
Main Results:
- Newborns showed distinct reactions to taste, with a stronger response to saline than tartrate.
- Infants with severe brain damage displayed an initial strong taste response that decreased over time.
- Normal infants generally showed a decrease in taste-elicited sucking response between 1 and 5 months of age.
Conclusions:
- Sucking response to taste in newborns is likely a primitive, subcortical reflex.
- This reflex diminishes gradually, similar to other primitive reflexes.
- The findings suggest taste perception in early infancy is primarily reflexive rather than cortically mediated.
Abstract:
Seventy-one full-term normal newborns were studied at the age of 5-7 days. A 0.1% tartrate or a 0.25% saline solution was given to each infant after 1-2 min of breast or bottle feeding and then the same solutions were once more given to the same subjects. Sucking rhythm was recorded and the infants' behavioral reactions were observed by examiners and analyzed on videotape. There were individual differences in the newborn's response to taste. Infants showed a similar response tendency to tartaric acid and saline solution, when given on two different occasions, respectively. But generally they reacted more strongly to saline than to tartrate. Next, sucking response to taste was studied in 20 infants once a month from birth until 5 months old. Five of them had severe brain damage and the other 15 infants were normal. The methods used were the same as those described in part 1. All 5 infants with severe brain damage initially showed a strong reaction and then a decrease of reaction. Fourteen normal infants were followed until 5 months of age: 12 of them showed a decrease of reaction between 1 and 5 months. Most of them showed decrement between 3 and 5 months. From our results, sucking response to taste in the newborns is assumed to be a subcortical reflex and not a cortically recognizable one. It might be called a primitive sucking response, which gradually decreases like any other primitive reflex does.