Psychology Grand Rounds
Functional neuroimaging of integrative processes in visual cortex
The integration of information is an important mechanism in perceptual processing that helps us to make sense of the world. In this talk, I will present work from my PhD, in which I studied integrative processes in the visual cortex. Using multi-voxel pattern analysis (MVPA), I investigated three levels of information integration. First of all, correctly integrating the components of a stimulus is crucial to create a coherent percept. In study 1 we asked how two superimposed moving gratings are integrated to form the percept of a moving pattern, referred to as pattern motion. Previous research found evidence for pattern motion processing only from V2 onwards, and especially in MT or hMT+/V5. However, we found pattern motion information as early as in V1. In addition to integrating the information within a stimulus, we also need to be able to integrate information across stimuli, reaching us through different senses. The neural mechanism that may enable the integration of information from different modalities was studied in the second project. Here, we studied tactile and visual motion direction processing in area hMT+/V5, an area traditionally considered to only process visual motion. We found that hMT+/V5 processes the motion direction of both visual and tactile moving stimuli, supporting the notion of hMT+/V5 as a multimodal area. Lastly, we are also capable of integrating abstract cues, e.g., those representing the motivational value of a stimulus. In the third project, we investigated the influence of reward on visual perception. We induced binocular rivalry, yielding alternating perception of two stimuli. One of the two percepts was associated with an auditory cue indicating monetary reward. By decoding the percepts from the visual cortex with MVPA, we found that the mean dominance duration of the rewarded percept increased compared to the neutral stimulus. In all three studies, we observed effects in areas that played a subordinate role in traditional views, redefining the role of the visual cortex in integrative processes.