Slow Potentials in Anticipatory Behavior

Abstract

Almost 40 years ago two papers appeared with an important impact on the psychophysiological and neurophysiological literature. Kornhuber and Deecke (1965) published their first recordings of the Bereitschaftspotential (BP), brain activity preceding a self-paced movement, while Walter et al. (1964) presented their study on the contingent negative variation (CNV). Recently Jahanshahi and Hallett (2003) edited a book on the BP, demonstrating that the topic is still of interest for many researchers. Both potentials reflect processes that are future-directed, coupled to an upcoming event that will take place within a few seconds. The subject, whose brain activity is recorded, has a notion about what is going to happen and when it is going to happen. The event may be the execution of a self-paced movement or the presentation of an informative stimulus with behavioral consequences. Preparation of a movement or anticipation of an upcoming stimulus goes along with behaviorally hidden processes that result in a better performance. Apart from the event, the timing is an essential aspect of each future-directed behavior. Certainty about when an event will take place allows better preparation and, therefore, a more adequate behavioral result. Both readiness potential (RP) and CNV are recorded under experimental conditions. A real life situation is transferred to circumstances that can be kept constant, in order to allow conclusions about the only experimental factor the investigator is interested in. The investigator asks the subject to do something, and the subject agrees to do so. All experiments are based upon this implicit agreement. If we ask a subject to press a button every 5 s, we call that movement self-paced because the subject does it voluntarily. However, at the same time he has to keep the instruction in a working memory system for the time of the experiment. In animal research we train subjects and reinforce the behavior we would like to see. Many monkey studies have been done in which BP, CNV, or unit activity have been recorded. Under these circumstances the animal is doing what he does in order to get the reinforcement. Thus, in all such experiments it is not only the task at hand but also the impending reinforcement, which has to be taken into account when interpreting the data. Grunewald and Grunewald-Zuberbier (1983, 1984) were among the first to record slow potentials not only prior to a movement, but also during the movement. Lang et al. (1984) also recorded brain activity during stimulus-guided movements. Under these circumstances slow potentials reflect the ongoing control of motor activity. In a more abstract situation subjects might be involved in memory search processes, which are also accompanied by slow waves, now reflecting the search for a specific item among a number of alternatives (Ruchkin et al., 1995; Rosler et al., 1995). While slow potentials in such settings reflect an on-line control of specific brain functions, this is not the topic of the present issue. Rather we concentrate on the use of slow potentials in anticipatory behavior. The late wave of the CNV is a combination of a movement-preceding negativity (MPN) and a stimulus preceding negativity (SPN; Brunia, 1988). To investigate anticipatory attention a time estimation task was used, in which both slow potentials can be separated in time. In the first contribution, van Boxtel and Bocker give an overview of the studies of the SPN. They show that the SPN is not restricted to the time estimation task, and that, apart from anticipatory attention, an emotional anticipation plays a role in the emergence of the SPN, too. While van Boxtel and Bocker stayed away from the CNV in order to study anticipatory processes not confounded with any motor activity, Leuthold, Sommer, and Ulrich use the CNV explicitly to investigate motor preparation. In their review they show that the application of the lateralized RP (LRP), derived from the CNV and not from the RP, is an interesting tool with which to investigate behaviorally hidden stages in motor preparation. Next, Journal of Psychophysiology 18 (2004) 59–60 © 2004 Federation of European Psychophysiology Societies