Institution: University of Nevada Reno
Talk Title: Mosaic of functional specificity for spatial and object-based tasks throughout the multiple demand network
Abstract: Visual tasks activate regions throughout the parietal, frontal, and inferior temporal cortex. Past work has found that many of these regions are similarly activated by a wide variety of tasks and consequently these regions together have been called the Multiple Demand (MD) network. Evidence for functional specificity by visual task in these regions has been sparse. We search for such functional specificity here. To this end, we recorded BOLD fMRI responses as human subjects viewed walk-throughs of a virtual 3D map while performing one of three tasks. Participants passively fixated, kept track of their original heading, or kept track of whether one of two target objects had appeared. At the end of each trial, they indicated whether a probe stimulus matched their current heading or the identity of any target. The task structure assured that participants continuously attended to task-relevant information throughout each trial. To dissociate stimulus-driven responses from task-driven responses, the same stimuli occurred in multiple task conditions. We modeled the BOLD responses as a function of either task identity or image-computed features of the stimulus (motion energy and other features). We found that the task model explained unique variance independent of the stimulus-driven models in parietal, frontal, and inferior lateral occipital cortex. We additionally found unique variance explained by task in a region anterior to hMT+ which has not previously been associated with the MD network. Among these regions, we found distinct sets of regions associated with the heading task and the search task. Responses in inferior LOTC were most modulated by the search task, the region near hMT+ by the heading task, and responses along the IPS alternated between the two tasks in a consistent pattern across participants. These results suggest a mosaic of functional specificity for spatial and object-based tasks throughout the MD network.