Attention capture by significant stimuli: semantic analysis follows attention switching

Escera, C.1, Corral, M. J.1, Yago, E.1, Corbera, S.1, and Nuņez, M. I.2
1Neurodynamics Laboratory, Department of Psychiatry and Clinical Psychobiology, University of Barcelona, Spain; 2Department of Behavioral Science Methods, University of Barcelona, Spain

Event-related potentials (ERPs) were recorded from the human scalp to resolve an old controversy in auditory attention research, namely, when the "breakthrough of the unattended" takes place in the human brain. Nine subjects classified visual stimuli occurring after task-irrelevant standard tones (p=0.8) or "novel" environmental sounds (p=0.2) into odd/even categories. After the recordings, subjects scored the novel sounds as to whether they had any particular meaning to them (identifiable) or were perceived just as a short burst of noise (non-identifiable), and performance and ERPs were analysed according to this classification. Results yielded identical N1 activity for the two types of novel sounds, indicating that attention switching was similarly triggered after these two types of unexpected sounds. However, there was a larger orienting of attention towards identifiable novels, as indicated both by larger behavioural distraction and enhanced novelty-P3 amplitude to these sounds. Moreover, this larger orienting of attention was due to the sounds being contingent with the visual stimuli, as no increase in novelty-P3 to identifiable novels was observed in a control condition, in which the sounds occurred non-contingently with the task-relevant visual stimuli. Therefore, the present results show that involuntary orienting of attention towards significant stimuli, such as our own name, occurs only after a transitory attention switch towards the eliciting stimuli.