Two experiment with college students, are planned using a Sternberg-like task with a stimulus display of four characters. Stimulus evaluation (memory set size = 2 vs. 4) and response type (Exp. 1: compatible vs. incompatible with the stimulus, Exp. 2: motor program sequences with lengths of 1 vs. 3) will be varied under conditions that promote either serial or parallel information processing (information obtained from the stimulus display vs. prior information from blocked trials). Scalp EEG will recorded and reaction time, latency of the P3 component of event- related potentials, and accuracy of performance will be measured. The following two hypotheses regarding the relationship between response processes and P3 latency will be tested: (1) A response that is incompatible, as opposed to compatible, with the stimulus will lengthen reaction time (RT) when either serial or parallel processing is promoted, but will lengthen P3 latency only when parallel processing is promoted, and (2) Increasing the length of a finger sequence motor program lengthen RT when either serial or parallel processing is promoted, but will not affect P3 latency under either processing condition. This research is important because event-related potential methodology has been used in pharmacologic studies as an aid in assessing drug effects on cognitive processes, as well as an aid in understanding cognitive processes in specific populations such as psychiatric patients and the elderly. In utilizing this methodology, P3 latency, assumed to be independent of response processes, has been included as a marker for the relative time taken for completion of stimulus evaluation processes. However, this approach may have limitations because there are circumstances under which P3 latency reflects response, as well as stimulus, process manipulations. The goal of the proposed research is to further our understanding of the task, response, and processing parameters under which P3 latency is affected by response processes.
