The late positive complex. Advances and new problems.

In summary, what we have tried to do in this paper is to present our view of the ways in which the ERP field has become more complex in recent years. It is not an overstatement to say that, in a certain sense, we know less now than we thought we knew five to ten years ago. New advances have brought with them new problems. But they also point, though not yet with complete clarity, to directions for new solutions. Possibly, as we make further progress toward the definition of various generators for different components, our problems may be simplified. But even this prediction cannot be made with certainty. It should be noted that we have tended in this chapter to emphasize the problems. There has also been a positive side to the recent developments. Because we are more aware of the overlap problem, we now work with methods that attempt to deal with it. We now know, for example, that P3b and SW can relate quite differently to behavioral variables. Decision time, which we had thought occurred at P3 latency, can now be assumed on the basis of recent findings to occur earlier, at the N2 component. The separation of the formerly unitary CNV into several components makes it more possible to develop unique functional roles for each of the components. A similar development has occurred with the separation of the poststimulus negativities into several components. Our constructs for various components are still on the fuzzy side, but the field has better tools at its disposal for making them more precise. Finally, the multiplicity of components, which appears overwhelming initially, provides us with more degrees of freedom in attempting to relate electrophysiological activity to behavior. A number of investigators have commented that the complexity of factors that enter into behavior could not be reflected in the relatively few ERP components we were dealing with. Now that more components are coming to be distinguished, the likelihood increases that we may be able to obtain ERP correlates of more of the dimensions involved in behavior.