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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.
