Investigation of Brain Regions Responsible for The Processing of The Stimulus Novelty by Using Functional Magnetic Resonance Imaging.

INTRODUCTION

Novelty processing is one of the basic survival mechanisms for living organisms. Among the various types of novelty, stimulus novelty is the effect created by stimuli that are unlikely to be encountered throughout one's lifetime. However, the oddball design mostly used in studying stimulus novelty also includes an obligatory contextual novelty effect, which actually requires the presence of schemas about sensory input in the memory. In this study, we aimed to investigate the neural circuits related purely to the detection of stimulus novelty using functional magnetic resonance imaging (fMRI) by applying an experimental design that excludes any contextual novelty effect.

METHODS

Fifteen right-handed healthy participants were included in the study. The stimulus novelty effect was generated by the images of object-like structures that could not be named and did not correspond to a real object. These stimuli were shuffled with images of familiar objects frequently encountered in daily life. SPM12 and CONN were used for the preprocessing stages and activation analysis of fMRI data. In the analyses, the cluster formation threshold was determined as p <0.001 and the cluster level significance threshold with family-wise error (FWE) correction was set at pFWE <0.05.

RESULTS

The activity of the fusiform, middle occipital, inferior occipital and superior occipital gyri increased during the processing of the stimulus novelty, while the activity of the inferior parietal cortex and supramarginal gyrus decreased.

CONCLUSION

With the experimental paradigm that excluded the confounding effects of contextual novelty, anatomical regions that respond specifically to stimulus novelty could be identified. Our results suggest that, while stimulus novelty intensively activates brain areas related with higher-order visual processing, the brain regions that associate sensory inputs with the schemas in the memory are less active.