Institution: University of Nevada Reno
Poster Title: Different tasks performed on same objects result in functionally distinct activation of LOTC and IPS
Abstract: Humans interact with the same objects in different ways based on the task at hand, and correspondingly, brain responses to the same objects can be modulated by task demands. Flexible perception is thought to rely on a network of areas termed the Multiple Demand Network (MDN), spanning parts of the parietal, frontal, and lateral occipital cortex. Here, we investigate the degree of functional specificity vs domain generality among regions in the MDN. To this end, we constructed an fMRI experiment in which human participants made judgments using different features of the same object. For each trial, participants either passively fixated or indicated whether a) medial axis structure or b) set of local shapes comprising the object or c) object texture was different from that of the previous object. Performing multiple tasks while presenting the same stimuli allows the study of task-specific responses independent of the stimuli. We created an encoding model with indicator variables for task conditions to derive weights associated with each task for every voxel. This model explained unique variance in a withheld portion of the dataset over and above stimulus-based models in regions of the frontal, parietal, and lateral occipital cortex. Principal Component Analysis of task weights across task-selective voxels revealed that less than half the variance was explained by a component indicative of activation across all tasks. Furthermore, contrast analysis of weights pointed to a significant number of voxels more tuned to specific tasks as opposed to uniform activation across all three tasks. Among these regions, we found that posterior LOTC ventral to hMT+ and dorsal to OFA responded more in the local shape task. A region just anterior to this responded more in the medial axis task. The texture task engaged more posterior regions. We also found spatially distinct activations in the IPS for different tasks. Although these varied across participants, some regions including lateral IPS were reliably activated by the medial axis task. These results point towards functional specificity of regions within the MDN, with different regions representing relatively more global and local aspects of object shape.