Intra- and inter-modal effects of prior stimulation on cardiac responsiveness to repeated stimulation in the human newborn.

The effect of prior equivalent auditory and somesthetic input on cardiac acceleration responses to repeated auditory and somesthetic stimulation was studied in 56 healthy 2- or 3-day-old infants. Responsiveness to initial presentation of the reiterative auditory stimulus was significantly greater than to the reiterative somesthetic stimulus regardless of the modality stimulated during the preceding series. In contrast the course of response decrement to subsequent repeated presentations of both stimuli was significantly more rapid when the reiterative and prior stimuli were in different modalities (inter-modal) than when they were in the same modality (intra-modal). The findings demonstrate a modality difference in effect of anticedent input on initial responiveness and a greater efficacy of inter- than of intra-modal auditory and somesthetic stimulation for the habituation of neonatal cardiac responses to repeated stimulation.