Interactions between space-based and category-based attention in the ventral and dorsal visual system during real-world visual search

摘要

??Humans are extremely efficient at detecting object categories (e.g., people) in briefly presented natural scenes. Recent work investigating the neural mechanisms underlying this ability suggests that rapid object category detection is supported by the implementation of top-down category-based attention signals that enable efficient target processing through the pre-activation of category-selective neurons in object-selective occipito-temporal cortex (OSC). A separate line of research in our lab has recently demonstrated that topographically organized regions in the parietal cortex (e.g., posterior IPS areas) that are involved in the generation of space-based attention signals also demonstrate object-selective responses. Here we used fMRI with a MVPA approach to investigate the relationship between object category-specific and space-based attention signals in OSC and IPS areas. Participants were briefly presented with natural scenes to both the left and right of a central fixation cross. On separate runs, participants spatially attended to either the left or the right scene. At the beginning of each trial, a central cue instructed participants to detect either people or cars in the to-be-attended scene. The extent to which consistent object category information was present in scene-evoked activation patterns was estimated by testing how similar they were to the activation patterns evoked by isolated object category exemplars that were presented in separate runs. Consistent with previous findings, the task-relevant category was represented more strongly in OSC than the currently irrelevant category. This was true both for spatially attended and spatially unattended scenes, suggesting that category biases are implemented independent of spatial information. Responses in the posterior IPS regions contained similar category-specific information, however in a spatially-specific manner. These results suggest that in addition to generating space-based control signals, posterior IPS regions may play a role in the control of category-specific biases that are implemented in OSC in a spatially unspecific manner.