An fMRI analysis of object priming and workload in the precuneus complex.

Drawings depicting familiar objects and unreal structures were presented twice, and participants (N=16) determined whether line drawings were real (familiar) or unreal (unfamiliar). The second presentation (repetition) of a drawing was typically responded to faster and more accurately than the first presentation and was accompanied by reduced activation in occipitotemporal (fusiform) and lateral precuneus regions, and increased activation in medial precuneus regions. The behavioral effects and reduced activations (e.g., lateral precuneus) on the second presentation were less pronounced for unreal objects than for real objects. Activation changes in the medial precuneus - increased activation on repetition and reduced activation for novel unreal objects - was further supported by the increased activation in this area during rest and reduced activation when workload was increased (i.e., processing novel unreal objects). The results from the present study in conjunction with those from several previous studies converge on the conclusion that the occipitotemporal and lateral regions of the precuneus are primarily involved in object priming, whereas the medial portion of precuneus primarily activates and deactivates as a function of workload.