engleski

Context determines neural correlates of deviant detection

Setting perceptual expectations can be based on different sources of information which determine the functional networks involved in implementing preparatory top-down influences and dealing with situations in which expectations are violated. The present study addressed the process of forming and violating expectations based on information of different origin, type and specificity within two types of task contexts. In the serial prediction task participants monitored ordered perceptual sequences for predefined sequential deviants, while the target detection task entailed a presentation of stimuli which had to be monitored for predefined non-sequential deviants. The two comparably designed tasks were presented in a mixed trial design and contained the same amount of physical information, differing in the nature and specificity of expectations which could be formed within the two contexts. Detection of sequential deviants triggered an increase of activity in lateral and mesial premotor and cerebellar areas which were initially supporting regular sequence processing. This pattern of activity is suggested to reflect detection of a mismatch between the expected and presented stimuli and updating of the underlying sequence representation (i.e., forward model). Presented violations additionally triggered activations in frontal areas initially not involved in sequence processing, reflecting the subsequent elaboration of the violation which required more cognitive control when compared to sequence repetition. In contrast, detecting non- sequential deviants triggered primarily bilateral activations within parietal and posterior temporal areas with an additional involvement of right superior and middle frontal gyrus, reflecting an increase in perceptual and attentional processing evoked by the non-sequential deviant. This pattern of results is comparable to the involvement of this network in detecting rare events in the oddball paradigm which is similar to the target detection task used in this study (e.g., Linden et al., 1999). The results of the present study indicate involvement of distinct networks in detecting different types of events deviating from a standard context defined by stability or continuity of presented events. This suggests that brain correlates of detecting different types of deviants reflect the nature and the origin of predictive processes underlying the expectations being violated.

deviant detection; prediction; premotor cortex; prefrontal cortex; sequencing

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