The effects of task relevancy on the late components of the auditory event-related potential in 6 month old infants

Infant cognition has traditionally been studied using a wide range of behavioral measures. These methods have a low temporal resolution, often incorporate an overt behavioral response as a dependent measure, and interpret failure to perform the behavioral response as an inability to perform the cognitive operation. It is possible that an inability to make or maintain a specific behavioral response might be misinterpreted as an inability to perform the cognitive operation, leading to an underestimation of the cognitive abilities of infants. The Event-Related Potential (ERP) can be obtained independently of an overt behavioral response and has a much higher temporal resolution than traditional behavioral methods. The P300 component of the ERP has been used in a variety of ways to study cognitive phenomena in adults. Based on the findings with adults, the P300 could be a useful tool in the study cognitive processes in infants, but it has yet to be definitively characterized in this population. Previous investigations of the infant ERP have revealed several components that may be related to cognitive processes, including one long latency positivity that appears to be similar to the adult P300. In order to determine if this positivity is indeed an early manifestation of P300 activity, it is important to investigate in infants those variables known to affect the adult P300. In the current study, a conditioning procedure was used to teach infants and adults an association between a target tone and the delivery of an attractive visual stimulus. This manipulation was intended to introduce the variable of Task Relevancy, a variable known to affect the adult P300. In the infant group, a late positive component that was larger in response to the target as compared to the non-target even in the absence of a probability manipulation was obtained. The pattern of results indicated that it was unlikely that the task was cognitively equivalent for infants and adults, precluding a comparison between adult P300 and infant late positive activity. The finding are nevertheless supportive of the notion that the late positive component observed in infants may be related to the adult P300.