Objects in context / MRI response to congruent and incongruent imagery

Abstract

Human beings are generally excellent at rapid object recognition, especially in isolation. However, objects are not viewed in isolation in the real world; instead, they are viewed within a context. This paper explores brain activity based on fMRI-measured blood-oxygen-level-dependent (BOLD) response using a task that is designed to test the ability of the brain to distinguish between congruent and incongruent objects within a scene. In this context, the quality of "congruency" describes the relationship between expected object size and the scene in which the object is placed. Analysis of the data obtained from this experiment showed a significant difference between brain activity when viewing an object in an incongruent or congruent context. Further, we can use support vector classifier (SVC) models to more sensitively predict whether a participant was looking at a congruent or incongruent object better than random chance. The findings of our analysis are consistent with current research in the field and offer a more detailed study of this neuroimaging finding. In our analysis, the fusiform face area was also found to be a strong predictor of congruency - a finding that is consistent with the most recent research in the field. Further, using searchlight analysis, we find voxels that discriminate on congruency in line with existing literature: the lateral occipital cortex and early visual cortex. However, areas that have received less attention are also strongly discriminant on congruency based on this analysis, namely the prefrontal cortex and caudate nucleus. Owing to these areas’ high activity during expectation-violations, we can conclude that the lateral occipital cortex and the early visual cortex are important to determining size-context relationship violations. However, the prefrontal cortex, caudate nucleus, and potentially other areas are also highly active and show congruency discrimination. This suggests involvement of a large part of the brain during object recognition and expectation-violation, and not the compartmentalised view of this process as older literature suggests. Lastly, activation within the fusiform face area was found to be a strong indicator of congruency