Tactile sensory capacity of the preterm infant: manual perception of shape from 28 gestational weeks.

OBJECTIVE Recent studies have shown that from the postconceptional age of 33 weeks, preterm infants are able to memorize tactile information about the shape of an object by using their hands, and can detect differences with another shape. This study aimed to investigate tactile abilities earlier on in development, in very preterm and mildly preterm human infants. METHODS Infants were assigned to 2 groups according to postconceptional age: very preterm (before 32 weeks) and mildly preterm (from 32 to 33+6 weeks). The test consisted of the repeated presentation of an object (prism or cylinder) in the left hand. The experiment was conducted in 3 phases: habituation (repeated presentation of the same object), discrimination (presentation of a novel object), followed by recognition (presentation of the familiar object). RESULTS Forty-eight newborns were recruited (24 very preterm; 24 mildly preterm). During habituation, each infant showed a decrease in the holding time of the object. Then, when a novel shape was put into the preterm newborn's hand, holding time increased. Finally, when the familiar shape was presented again, the holding time decreased. Preterm infants can memorize by touch specific features that differentiate prism and cylinder shapes, discriminate between them, and recognize them after interference. CONCLUSIONS From 28 weeks, and from the first days of life, the preterm newborn is endowed with tactile sensory capacities. The tactile stimulations that are presented to preterm infants during their hospitalization should be adapted while respecting their sleep-wake rhythms.