Habituation and laterality of orienting processes as reflected by slow negative waves.

The study is concerned with the question of whether the orienting wave (O-wave), a slow potential shift of the event-related brain potential, is a component of the orienting response (OR). As habituation is supposed to be the most important characteristic of the OR, we focussed particularly on any habituating aspect of the O-wave. Results suggest that its bilateral distribution over midfrontal areas might constitute such a link relating the O-wave to orienting activity. Hemispheric asymmetry linearly decreased its right-sided predominance in response to repeated presentations of an initially novel auditory stimulus. A similar, concomitant diminution of the skin conductance response (SCR) occurred. Both, the O-wave and the SCR varied, moreover, with signal value and electrodermal lability which are known to relate to the OR. Therefore we suggest the O-wave comprise features typical of a component of the OR. A hypothesis is put forward according to which the O-wave and its laterality are dependent on the ascending noradrenergic locus coeruleus system.