Fig 1.
Object-scene and object-location memory tasks.
In the object-scene task, subjects were first pre-familiarized with six scenes. During the study phase, subjects studied 36 trial-unique objects, each paired with one scene (six objects were paired with each scene) in randomized order. Three additional non-tested items were used as primacy and recency buffers. During the corresponding test, old objects were presented intermixed with an equal number of new objects. Subjects made old/new recognition judgments mixed with a confidence judgment. For all old items, subjects then selected the scene that was paired with the object. The object-location task followed a similar format, except that there were six possible screen locations instead of six possible scene associates. Object and scene images were respectively taken from publically available sources, which were described in Brady et al.[22] and Hannula et al.[23], with no copyright protection via the internet for display purposes.
Table 1.
Labels of ROIs in the task-positive network.
Table 2.
Labels of ROIs in the task-negative network.
Fig 2.
(A) Response rates for the recognition memory judgment are shown for the object-scene and object-location tasks, averaged separately for old versus new objects and for each confidence level (HC: high confidence; LC: low confidence) and each category of response accuracy (hit, miss, FA: false alarm, and CR: correct rejection). (B) Response rates for source memory judgments are shown averaged based on accuracy/confidence of the corresponding recognition response (SRC: source recollection correct, SRIC: source recollection incorrect). Trials with correct source recollection tended to include objects that were recognized with high confidence. Error bars indicate the standard error mean.
Fig 3.
Task-related networks and modular structure.
(A) Locations identified as task-positive (red) and task-negative (blue) (see Tables 1 and 2). These regions were identified via lenient univariate analysis coupled with anatomical demarcation for use as ROIs in subsequent connectivity analyses (see text). (B) Connectivity matrix for the object-scene task, sorted by identified modules, (Left) and the identified modules (Right) (C) Connectivity matrix for the object-location task, sorted according to the identified modules for the object-scene task (Left) and the identified modules (Right).
Table 3.
Summary of network interaction associated with memory formation.
Fig 4.
Correlation of source memory accuracy with module-level interaction.
(A) For object-scene association task, interaction between two task-negative modules shows positive correlation (R2 = 0.50, Pcorr < 0.001) and interaction between task-positive module and task-negative module shows negative correlation (R2 = 0.46, Pcorr < 0.001). (B) For object-location association task, interaction within a task-positive module shows negative correlation (R2 = 0.34, Pcorr = 0.017).