Studying the interaction between top-down and bottom-up processes during ambiguous perception

There is a view that the brain processes sensory information through the interaction between two types of processes, bottom-up and top-down. Bottom-up processes originate in the sensory areas at the earlier processing stages and process the stimulus details. Top-down components occur in the anterior cortical sites carrying information about the internal state of the subject, their mental state, and experience. Modern neuroscience relates bottom-up components with the high-frequency EEG rhythms, while low-frequency rhythms subserve the top-down ones. The interaction between the top-down and bottom-up processes attracts the attention of scientists worldwide, but numerous important questions remain unresolved. In this lecture, we address this issue by using an ambiguous stimuli paradigm, Necker cubes. When the Necker cube is unambiguous, the contrast of the inner edge defines its orientation, left or right. When the cube is unambiguous, the morphology of inner edges barely defines orientation. We suppose, that in the first case, the observer uses bottom-up mechanisms to process the cube’s morphology. In the latter case, they mostly rely on top-down mechanisms. Thus, manipulating the image ambiguity, we expect the prevalence of the bottom-up processes over the top-down and vice versa.