Learning to react: anticipatory mechanisms in children and adults during a visuospatial attention task.

OBJECTIVE: To investigate the mechanisms underlying age-related improvement in response times during forewarned motor tasks, using reaction times (RTs) and event-related potentials (ERPs) during a variant of the Posner paradigm.
METHODS: Children and adults reacted to visual targets preceded by a spatial cue.
RESULTS: As expected, adults responded faster than children whatever the cue-target combination, but this advantage could not be explained by differences in attentional orienting to, or detection of, target stimuli. ERP differences between children and adults corresponded almost exclusively to the period preceding target stimuli, where adults, but not children, exhibited a slow negative wave that extended from the delivery of the cue to slightly beyond the presentation of the target. CONCLUSIONS AND SIGNIFICANCE: The timing, morphology and topography of this slow negativity corresponded to those of 'Contingent Negative Variation' and 'Readiness Potential' processes. We argue that the relative slowness of motor reactions in children during this task was not due to a deficit in spatial orienting or target evaluation, but rather to a failure in developing anticipatory and preparatory reactions in response to cues, i.e. a deficit in executive functions.