Figure 6. Interaction between task and load at retrieval.

L =  Low load, M =  Medium load, H  =  High load, Pic  =  Picture task, Pos  =  Position task, Com  =  Combined task. A. Group mean activity for the task x load interaction at retrieval (Combined < averaged [Picture + Position] x Medium > Low) is superimposed on the SPM high resolution single subject T1-weighted image. Activity depicted is significant using a cluster-defining whole brain threshold of p<0.001 and FWE (p<0.05) cluster correction. B. A task-negative mask was created by applying a contrast isolating negative responses (below baseline) for all (task and load) conditions. Group mean activity is superimposed on the SPM high resolution single subject T1- weighted image. Activity depicted is significant using a cluster-defining whole brain threshold of p<0.001 and FWE (p<0.05) cluster correction. C. An inclusive mask was applied to form an intersection of regions common to the interaction effect and the task-negative mask. Group mean activity is superimposed on the SPM high resolution single subject T1- weighted image. Activity depicted is significant using a cluster-defining whole brain threshold of p<0.001 and FWE (p<0.05) cluster correction. D. Mean parameter estimates (β coefficients) for each task and load are shown for the peak voxel in the posterior cingulate cluster observed following inclusive masking of the task x load interaction and the set of task-negative regions (at corrected cluster threshold) shown in Figure 6C. As depicted in the plot, greater deactivation is observed between Low and Medium loads for the Combined task relative to the Picture and Position tasks. The beta estimate for the High load are also included in the figures to depict relative effects between load levels in the Combined task, however the main task effects were based on Low and Medium loads. Error bars represent ±1 standard error of the mean.