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Abstract

The goal of the present thesis was to explore the process of detecting a certain category of deviant events, namely sequential deviants presented within the context of predictive perceptual processing as explored using sequences of visual stimuli. These events violate expectations formulated within perceptual sequences whose structure is defined by the order of stimulus presentation. In the first two experiments conducted within the present thesis, the detection of such sequential deviants was compared to the detection of feature deviants which violated the expectations formulated based on perceptual features of individual stimuli. The results from both experiments indicated a dissociation between the processing of these two types of deviants. This was shown both on the level of temporal dynamics as well as the brain areas engaged in processing feature and sequential deviants. Following this, the processing of sequential deviants was additionally investigated within perceptual sequences defined by different stimulus features and on differing levels of specificity. The obtained findings indicate a partly overlapping, but not uniform pattern of activations supporting the detection of sequential deviants. This suggests that specific factors defining the sequential structure strongly influence which brain regions become engaged in processing violations introduced in such sequences. The most important of these factors is the stimulus property defining the sequence and the characteristics of sensorimotor transformations it affords. In addition, the specificity of expectations which can be formulated within the sequence also influences the engagement of brain regions in detecting sequential deviants. Finally, although not explicitly explored, the influence of other sequence properties, e.g., number of sequence repetitions within the trial, might also modulate the involvement of the identified brain networks in detecting such events. In conclusion, detection of sequential deviants does not represent a uniform process, but is highly dependent on the properties of regular sequences which determine the nature of expectations being formulated and consequently violated by the presentation of such events.