Maturation of startle facilitation by sustained prestimulation.

The startle response to a 104dB (SPL) 50-ms burst of white noise was facilitated by prestimulation with a nonstartling tone sustained for 2 s prior to the startling stimulus in 3, 4, 5, and 8 year old children and young adults. Both startle amplitude and onset latency showed significantly greater facilitation in the preschool children than in the 8-year-olds and adults. The results of this experiment, which used a fixed prestimulation interval, were compared to those of an earlier study in which the prestimulation interval was varied. The maturational changes in startle facilitation in response to the 2-s prestimulation interval were similar in the two experiments. Hence the maturational effect on startle facilitation was independent of the uncertainty (as to when the startling stimulus would be given), which might be associated with variable prestimulation intervals. These findings suggest that the neuronal mechanisms that mediate startle facilitation undergo development during early childhood and mature about 8 years of age, and that this maturational sequence is relatively independent of attentional effects.