Abstract: Studies have long suggested that neonates’ movements and responses to external stimuli were the product of reflexive reactions and not purposeful movements. However, research into the effect of purposefully chosen stimuli for sound, taste, smell and sight have indicated that newborns can recognize and prefer sensations that they have encountered either while in the womb or immediately after birth. Research indicates that newborns will increase sucking when it encounters an odour it is familiar with.
A baby who hears the sound of his mother’s voice will orient his head in the direction of that sound. Infants obviously prefer the taste of certain things (specifically those that are sweetened) to other tastes. Finally, visual stimulus can create purposeful reaching movements in newborns and young infants even though this sense is the least developed. This study seeks to review that literature and present an analysis of the impact it could have for the treatment of brain-damaged newborns.
The impact of this research is most exciting for applications that would have an infant make a purposeful movement, especially as a means for early intervention and rehabilitation. Introduction: It has been believed previously that neonate’s responses to sensations were reflexive and not volitional (). Several studies have challenged those beliefs, and investigated babies’ responses to stimulation of individual senses and their relationship to movement. It has been discovered that the sensory functions of infants begin before birth and become more mature after birth ().
This paper looks at separate studies that have been devoted to understanding the relationship between an infant’s senses (i. e. taste, smell, audition and vision) and his/her movement. By far the most studies investigate neonatal vision but there are also studies investigating hearing, smell and taste. The surprising information gleaned from the studies I have examined indicates that an infant’s behaviour is flexible and that apparently goal-directed actions result from stimulation of their senses. These actions may occur even from as early as few hours after birth.
Understanding these senses, and perceiving how they can be used to elicit or promote voluntary movement is likely to open new and exciting opportunities for early rehabilitation therapy for babies with perinatal brain damage. Taste: Taste is one of the chemosenses that belongs to the sensory system. It occurs when chemical molecules released by substances stimulate gustatory cells or the taste receptors which are clustered in the taste buds located in the tongue and the oropharynx. These receptors transmit the sensory signals to particular centres in the brain where specific tastes i. e.
sweet, salt and bitter are identified. It has been reported that the taste buds appear around the 7th or 8th week of gestation, and look a lot like the adult’s taste buds by 13-15 weeks of gestation 1 and that a well- developed sense of taste before birth sets the stage for early learning. Several studies have reported that as early as a few hours after birth, newborns are able to respond to the taste of different substances2, 3 which have been assessed using qualitative and quantitative measurements like the calming effect of the substances administered, facial expressions, mouthing, and hand-mouth contact.
2-8 From a therapeutic point of view the possibility of eliciting movements such as hand to mouth movements from taste is potentially very important, only the studies that looked at the possible stimuli that can elicit and/or promote this behaviour in newborns and the proposed mechanism behind this behaviour will be reviewed. Rochat et al 9 noticed that hand-mouth activity is stimulated through the use of a very small dose of intra-oral sucrose solution. This behaviour remained with repeated sucrose administration, and withdrew by its termination.
Further, they noticed that there was a significant shift in the infant’s general movement toward hand-mouth contact after sucrose delivery compared to baseline period i. e. no fluid administration period. Butterworth and Hopkins 13 filmed the spontaneous arm and hand movements of healthy newborns. Microanalysis of the films revealed that the majority of arm movements which resulted in contact with any part of the head lead to contact with the mouth either directly or indirectly.
They also noted that the movements that landed on the mouth were preceded by open mouth posture, this behaviour was seen more when the infants were hungry than after they had been fed. 14 Furthermore, through measuring the force of palm pressure, Buka and Lipsitt 15 found that newborns grasping behaviour is increased when sucking and the effect is even greater when babies are sucking a sucrose solution. It has been proposed that in order for the hand-mouth behaviour to occur, two conditions have to be met: 1) newborns have to be in an active stage i.
e. Prechtl state 5: eyes open or closed, fussing or crying () , because administering sucrose to a calm newborn did not promote the hand-mouth behaviour, 2) the suckling system must be stimulated through the administration of sugar solution in the mouth. 6 Hand-mouth contacts have been elicited and/or promoted by sucrose, 4-7, 9, 10 and aspartame, 4 but not by quinine, corn oil, 6 polycose, 4 breast-milk, 11 or infants’ formula 12 .
These studies provide evidence that the occurrence of the hand-mouth contacts is a stimulus dependent and related to the degree of sweetness of the orally administered substances. For instance, Blass et al 7 and Rochat et al 9 showed that by delivering a . 20 ml of a 12 % sucrose solution using a sterile syringe into newborn’s mouth midline the hand-mouth contacts increased with repeated sucrose stimulation and reverted to the baseline with sucrose termination .
Barr et all 4 reported that frequency of hand-mouth contact is not related to the nutrition class (carbohydrate / versus amino acid), but to the sweetness of the substance used. In their study they found that sucrose (carbohydrate) and aspartame(an amino acid), both of which taste sweet both increase the frequency of hand-mouth contact compared to polycose, which belongs to the same nutritional class as sucrose, but is less sweet.
Their findings are supported by another study done by Graillon et al 6 which found that non-sweet substances like quinine and corn oil did not induce hand-mouth contacts in newborn infants. In line with Von Hofsten premise that goal directed movements form part of an infants’ general movement, Butterworth and Hopkins 13 suggest that hand-mouth contact has all the characteristic of a goal-directed movement, but because the baby is unskilled the intentional outcome occurs inconsistently.