Functional brain organization of preparatory attentional control in visual search

• Brain areas activated when preparing to search for a visual target are isolated.
• Only posterior brain and sub-cortical areas are activated.
• By increasing anticipated difficulty, identical targets produce new neural activity.
• Intra-parietal activation is not part of a fronto-parietal control network.
• Preparing for an easy or difficult search activates the striatum.

Looking for an object that may be present in a cluttered visual display requires an advanced specification of that object to be created and then matched against the incoming visual input. Here, fast event-related fMRI was used to identify the brain networks that are active when preparing to search for a visual target. By isolating the preparation phase of the task it has been possible to show that for an identical stimulus, different patterns of cortical activation occur depending on whether participants anticipate a ‘feature’ or a ‘conjunction’ search task. When anticipating a conjunction search task, there was more robust activation in ventral occipital areas, new activity in the transverse occipital sulci and right posterior intraparietal sulcus. In addition, preparing for either type of search activated ventral striatum and lateral cerebellum. These results suggest that when participants anticipate a demanding search task, they develop a different advanced representation of a visually identical target stimulus compared to when they anticipate a nondemanding search.