Stimulus probability and event-related potentials of the brain in 6-month-old human infants: a parametric study.

The effects of a priori stimulus probability and local-stimulus sequences on the Nc, NSW and Pc components of the event-related brain potentials were studied in six groups of 6-month-old human infants. Predictions from memory, expectancy and attentional accounts of the Nc, NSW and Pc components were examined using an infant-control oddball paradigm in which visual stimuli were presented across groups, at 0.90/0.10, 0.80/0.20, 0.70/0.30, 0.60/0.40, 0.50/0.50 (alternation) and 0.50/0.50 (random) probabilities. The main results indicated that stimulus probabilities and local-stimulus sequences affected Nc amplitude and latency, NSW amplitude but not the Pc component. Concurrent visual fixation performance was also found to be influenced by stimulus probabilities. The results were discussed in terms of the predictions from memory, expectancy and attentional accounts of the infant late components.