Thesis defense Mariya Manahova (Donders series 569)

17 October 2022

Promotor: prof. dr. F. de Lange
Co-Promotor: Dr. E. Spaak

Familiarity and Expectation in Visual Processing

Many cognitive processes influence the way we perceive the world. In particular, forms of prior knowledge such as being familiar with an image or expecting to see an image can affect perception. This PhD thesis examined how familiarity and expectation modulate the neural signal in the human visual system. The first chapter provided an overview of the literature on the topic and explained the background for the research questions we asked. The research conducted for this thesis included three experiments with magnetoencephalography (MEG) recordings and one experiment using behavioral measures, all conducted in healthy adults. The second chapter, which described the first MEG experiment, explored whether the neural effects of familiarity and expectation are additive, and we found that indeed this appears to be the case: both types of prior knowledge contributed to an amplitude difference in the neural signal, and familiarity led to increased signal truncation. The third chapter, which described the second MEG experiment, examined the temporal and spatial dynamics of familiarity-induced signal truncation in the human visual system. The results indicated that signal truncation is the highest for fast image presentation speeds and that it spreads laterally and anteriorly in the brain as the presentation speed gets slower. Furthermore, we found that target images were processed more strongly when embedded in familiar distractors. The fourth chapter, which described the third MEG experiment and the behavioral experiment, explored whether expecting object images leads to prestimulus template activation in the human visual system. The results of this study were inconclusive, meaning that we did not observe prestimulus templates elicited by object expectations. We discussed possible limitations of the study and improvements for future research. The fifth chapter summarized the findings of the empirical chapters, discussed the interpretations of the results we obtained, and considered the implications of our findings for some overarching questions that arise from this research. Finally, we discussed some considerations for future research on this topic. While there is much more to discover about the way prior knowledge influences our perception and the accompanying neural signals, this thesis has offered some important contributions to our understanding of our wonderfully complex brains.