Differential effects of experience on the ERP and behavior of 6‐month‐old infants: Trends during repeated stimulus presentations

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Abstract
Increasing experience with repetitive stimuli may lead to changes in the way the infant processes the information in the stimulus. It has been shown that some components of the event‐related brain potential (ERP) are sensitive to the differential experience provided by two stimuli presented at different probabilities. For example, the negative component (Nc) of the infant's ERP is often greater in amplitude to low probability stimuli (oddballs) than to frequent stimuli. Therefore, changes in ERP component amplitudes and latencies may be expected to occur with stimulus repetition. We analyzed the ERP components to the frequent stimulus within an oddball task for 28 six‐month‐old infants. An 80‐trial Benoulli sequence of two female‐face pictures, presented at 80%/20% probabilities, was divided into three blocks. Amplitudes and latencies of Nc and a positive component (Pb) were measured as was the area of a negative slow wave (NSW) at frontal and central scalp sites FZ, CZ, PZ, C3, and C4. Early components were measured at posterior scalp site OZ. There was a general trend for Nc amplitude to decrease across blocks at all central and anterior scalp sites but significantly decreased only at the central scalp (CZ). Similarly the component Pb generally increased in amplitude at all sites across blocks but was significant only at right central scalp (C4). There were no changes in NSW at any site, nor were there changes for the components at PZ and OZ. Visual fixation durations significantly decreased rapidly within the first block of trials. The data support the independence of these three ERP components and their association with different aspects of information processing. The different rates of change with stimulus experience of visual fixation as compared to the ERP components indicates that the infant is continuing to process the stimulus even when behavioral measures of attention are minimal. Both behavioral and ERP measures of attention are needed to more fully understand the development of information processing in infants.