Workload On Endogenous And Exogenous Attention Interactions On The Meaning Of ERP Research

Posner (1980) defined endogenous and exogenous controls of attention on the basis of activity. Endogenous attention is a voluntary system that directs information processing to a given location in response to a symbolic indicator, such as a central arrow (central cue) in visual field, while exogenous attention is a reflective system that orients to salient stimuli, such as a peripheral flash (peripheral cue). The relationship between endogenous and exogenous attention has been a focus of studies. The first views (Yantis et al.1984) hold that exogenous attention represents a fully automatic process, whereas endogenous attention represents a controlled one. Their subsequent study found that if an endogenous cue was100%valid and preceded the exogenous cue (an abruptly onset target), exogenous orienting response was inhibited. Thus,exogenous attention is not fully automated processing. Muller’s study also found that exogenous attention will have an impact on endogenous attention. Study of Berger et al (2005) proposed a more integrated view that task load will modulate the interaction between endogenous attention and exogenous attention. When task load is low, endogenous and exogenous attention will be independent of each other, while task load increases, endogenous and exogenous attention will interact with each other. But this study did not pay attention to different stages of information processing of endogenous and exogenous attention. In addition, whether endogenous and exogenous attention are two modes of an unitary processing system or two different system is still unknown. In this study, using Event-Related Potentials (ERP) technology to explore the different stages of information processing in the interaction of endogenous and exogenous attention under different task load.In this study, using an abrupt-onset paradigm (Yantis&Jonides,1990) and manipulating cue validity and onset type were conducted to study the competition between endogenous and exogenous controls of attention. A searching task was used as a low-load task, and a discrimination task as a high-load task to manipulate task load. It was found that in the low task load conditions, no significant interaction between endogenous attention and exogenous attention in reaction time, and in P1, N1and P300EEG component. In the high task load conditions, the interaction between endogenous and exogenous attention was significant in reaction time and in P1and N1component. But in P300component, the effect of endogenous attention was significant, but effect of exogenous attention and interaction was not significant.These results suggest that the control of the endogenous and exogenous attention in the low task load conditions was independent of each other, but in the high task load, because of the competition for limited cognitive resources, there was an interaction. This conclusion was shown in reaction time and P1, N1component. But endogenous attention had a prior effect on P300component in high-load task. We can conduct that endogenous and exogenous attention had an effect on early visual processing stage, but only endogenous attention affect the higher processing stage, P300. At last, endogenous and exogenous attention are two different system, but not two modes of an unitary processing system.