Abstract: A relevant development in the study of brain-behavior relations comes from experiments that measure neural activity using Electroencephalography (EEG). In a technique called Event Related Potentials (ERPs), EEG activity is time-locked to experimentally relevant events, such as stimuli presented to the subject, thereby isolating specific neural responses of interest. The P3A is a brain response distributed anteriorly on the human scalp. The label derives from the response consisting of a positive peak, occurring at approximately 300ms post stimulus presentation. The P3A response is typically obtained in a discrete trial three stimulus oddball paradigm in which a frequent stimulus occasioning a response (target) is alternated with an infrequent stimulus (nontarget). A third kind of stimulus - unrelated to the task (e.g. a dog barking) is presented, originating a P3A response. The P3A has been interpreted in the past as a response indicative of “novelty processing” or of an orienting response (e.g. Wetzel, N., Schröger, E., & Widmann, A. 2013). This study is an extension of a previous study in our lab by Ortu and Rosales-Ruiz (2015). Both studies used a free operant procedure of alternating FR5 and VR5 schedules of reinforcement. Our results are partially inconsistent with the traditional interpretation of the P3A, showing a larger P3A response following the stimulus preceding the consummatory response in the VR5 condition compared to the FR5 condition. In our experiment, the stimulus preceding the consummatory response does not differ in probability or physical stimulus properties across experimental conditions compared to traditional P3A experiments, pointing to the relevance of schedule effects in eliciting the P3A response and more generally to the importance of free operant procedures in characterizing neuroscientific events. |