Cortical Networks Involved in Memory for Temporal Order

Abstract

We examined the neurobiological basis of temporal resetting, an aspect of temporal order memory, using a version of the delayed-match-to-multiple-sample task. While in an fMRI scanner, participants evaluated whether an item was novel or whether it had appeared before or after a reset event that signified the start of a new block of trials. Participants responded "old" to items that were repeated within the current block and "new" to both novel items and items that had last appeared before the reset event (pseudonew items). Medial-temporal, prefrontal, and occipital regions responded to absolute novelty of the stimulus-they differentiated between novel items and previously seen items, but not between old and pseudonew items. Activation for pseudonew items in the frontopolar and parietal regions, in contrast, was intermediate between old and new items. The posterior cingulate cortex extending to precuneus was the only region that showed complete temporal resetting, and its activation reflected whether an item was new or old according to the task instructions regardless of its familiarity. There was also a significant Condition (old/pseudonew) × Familiarity (second/third presentations) interaction effect on behavioral and neural measures. For pseudonew items, greater familiarity decreased response accuracy, increased RTs, increased ACC activation, and increased functional connectivity between ACC and the left frontal pole. The reverse was observed for old items. On the basis of these results, we propose a theoretical framework in which temporal resetting relies on an episodic retrieval network that is modulated by cognitive control and conflict resolution.

Figure 1

Simplified task diagram. The number after the trial specifier (i.e., Old, Pseudonew, Old-repeat) indicates the number of times the specific image had appeared, thus far, in the task.

Figure 2

Response times and accuracy as a function of the number of times the item was presented during the experiment and the trial type

Figure 3

Brain activation for new items, old items on the second presentation (Old2) and pseudonew items on the second presentation (PN2) in (a) Left perirhinal cortex (PrC), (b) right PrC, (c) the right hippocampus (HPC), (d) Left intraparietal sulcus (IPS), (e) right posterior cingulate cortex (PCC)/precuneus. Error bars represent 1 standard error.

Figure 4

Activation patterns for New (N) vs Old2 (O2) vs Pseudonew2 (PN2) ANOVA, showing pair-wise comparisons, as labeled.

Figure 5

(a) The interaction between the trial type (Old/Pseudonew) and the presentation number (second/third) in the bilateral ACC (anterior cingulate gyrus); (b) The interaction in functional connectivity between ACC and left frontal pole (LFP), with ACC serving as a seed region.