Taste-elicited activity in facial muscle regions in 5-8-week-old infants

The state of development of the sense of taste in humans during the first few months of life is only partially understood. Since taste plays a critical role in the feeding and nutrition of infants a better understanding of taste development during early life is required. Currently, information about the sense of taste in pre-verbal infants is obtained by analysis of videotaped facial expressions using the Baby FACS coding system. A potentially more objective faster procedure for assessing facial expressions not investigated in infants is electromyography (EMG). The method has been successfully used to study taste-elicited responses in the mid-face muscle regions of the levator labii and zygomaticus major of 6-9-year-olds and in a range of facial muscle regions in adults. Accordingly, this study aimed to investigate taste in young infants using EMG to 1) measure activity simultaneously in 4 facial muscle regions in response to 3 common tastants and 2) determine whether the activities of one or more muscle regions is needed to provide evidence of perception of a tastant by an infant. The results indicated that multiple facial muscle regions responded simultaneously but differentially to non-sweet and sweet tastants and recordings of activities from 3 or 4 regions simultaneously indicated that almost 100% of infants responded to the unpleasant tastes of quinine and citric acid, and 80% to sucrose.