The present study investigates bottom-up effects serving the optimal balance between focusing attention on relevant information and distractibility by potentially significant events outside the focus of attention. We tested whether distraction, indicated by behavioral and event-related brain potential (ERP) measures, varies with the strength of task-irrelevant deviances. Twenty subjects performed a tone-duration discrimination task (200 or 400 ms sinusoidal tones presented equiprobably). The stimuli were presented with frequent standard (p = 0.84; 1000 Hz) or infrequent deviant (p = 0.16) pitch. These task-irrelevant pitch changes consisted in a frequency increase/decrease of 1%, 3%, 5%, or 10%. Each of them resulted in prolonged reaction times (RT) in the duration discrimination task and elicited the MMN, P3a, and RON components of the ERP. Importantly, these measures did increase as a function of pitch deviance. Separating the individual trials on the 1% deviation level into trials with and without RT prolongation, i.e., behavioral distraction effect, revealed that both subgroups had similar MMN, but P3a and RON were confined to the trials with RT prolongation. Results are interpreted within a model relating preattentive deviance detection, distraction, and working memory.

Traditional auditory oddball paradigms imply the brain's ability to encode regularities, but are not optimal for investigating the process of regularity establishment. In the present study, a dynamic experimental protocol was developed that simulates a more realistic auditory environment with changing regularities. The dynamic sequences were included in a distraction paradigm in order to study regularity extraction and application. Subjects discriminated the duration of sequentially presented tones. Without relevance to the task, tones repeated or changed in frequency according to a pattern unknown to the subject. When frequency repetitions were broken by a deviating tone, behavioral distraction (prolonged reaction time in the duration discrimination task) was elicited. Moreover, event-related brain potential components indicated deviance detection (mismatch negativity), involuntary attention switches (P3a), and attentional reorientation. These results suggest that regularities were extracted from the dynamic stimulation and were used to predict forthcoming stimuli. The effects were already observed with deviants occurring after as few as two presentations of a standard frequency, that is, violating a just emerging rule. Effects of regularity violation strengthened with the number of standard repetitions. Control stimuli comprising no regularity revealed that the observed effects were due to both improvements in standard processing (benefits of regularity establishment) and deteriorations in deviant processing (costs of regularity violation). Thus, regularities are exploited in two different ways: for an efficient processing of regularity-conforming events as well as for the detection of nonconforming, presumably important events. The present results underline the brain's flexibility in its adaptation to environmental demands.

The ability to encode rules and to detect rule-violating events outside the focus of attention is vital for adaptive behavior. Our brain recordings reveal that violations of abstract auditory rules are processed even when the sounds are unattended. When subjects performed a task related to the sounds but not to the rule, rule violations impaired task performance and activated a network involving supratemporal, parietal and frontal areas although none of the subjects acquired explicit knowledge of the rule or became aware of rule violations. When subjects tried to behaviorally detect rule violations, the brain's automatic violation detection facilitated intentional detection. This shows the brain's capacity for abstraction – an important cognitive function necessary to model the world. Our study provides the first evidence for the task-independence (i.e. automaticity) of this ability to encode abstract rules and for its immediate consequences for subsequent mental processes.

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When the two eyes of an observer are exposed to conflicting stimuli, they enter into binocular rivalry and the two possible percepts will alternate in dominance. We investigated neural activity and its time course following binocular rivalry by measuring human event-related brain potentials to transitions from rivalrous to non-rivalrous stimulation. When these changes did not entail a change in conscious perception they elicited a markedly attenuated N1 component and a delayed and attenuated P3 peak as compared to percept-incompatible changes and non-rivalrous control conditions. These results suggest that in humans binocular rivalry is resolved at latest in extrastriate visual areas.

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When something appears, how soon is the first neural correlate of awareness of it, and where is that activity in the brain? To answer these questions, we measured the electroencephalogram under conditions in which visual stimuli changed identically but in which awareness differed. We manipulated awareness by using binocular rivalry between orthogonal gratings viewed one to each eye. Then we changed the orientation of the grating to one eye to be the same as that to the other eye. Because of the rivalry, sometimes this happened to the visible grating, producing a clear change in perceived orientation, and other times it happened to the invisible grating, producing no change in perceived orientation. This procedure allowed us to analyze time-locked topographic scalp and tomographic primary current densities of the event-related potentials to physically identical events differing in their perceptual consequences. When the change in orientation reached awareness, neural responses began at about 100 ms, spreading mainly from dorsal occipital areas. When the change in orientation did not reach awareness, neural responses also began at about 100 ms, but they were attenuated, particularly in the right fusiform gyrus. We place the earliest correlate of visual awareness following binocular rivalry in the ventrolateral occipitotemporal cortex.