Dissociable neural routes to successful prospective memory

Abstract

Identifying the processes by which people remember to execute an intention at an appropriate moment (prospective memory) remains a fundamental theoretical challenge. According to one account, top-down attentional control is required to maintain activation of the intention, initiate intention retrieval, or support monitoring. A diverging account suggests that bottom-up, spontaneous retrieval can be triggered by cues that have been associated with the intention and that sustained attentional processes are not required. We used a specialized experimental design and functional MRI methods to selectively marshal and identify each process. Results revealed a clear dissociation. One prospective-memory task recruited sustained activity in attentional-control areas, such as the anterior prefrontal cortex; the other engaged purely transient activity in parietal and ventral brain regions associated with attentional capture, target detection, and episodic retrieval. These patterns provide critical evidence that there are two neural routes to prospective memory, with each route emerging under different circumstances.

Keywords: cognitive neuroscience; memory.

Figure 1

Green: sustained activations selective to the Nonfocal condition; Red: overlap of transient activations on both Focal and Nonfocal PM trials; Yellow: overlap regions showing both Nonfocal sustained and transient activations (in both conditions).

Figure 2

Sustained and transient effects in left aPFC ROI (8mm sphere at −34, 56, 9) for Focal and Nonfocal PM. PM Sus: sustained effect in PM block, CTL Sus: sustained effect in control block; PM: transient effect on PM trials (correct trials only); Ong-PM: transient effect for category decision task trials (ongoing trials) during the PM block; Ong- CTL: transient effect for ongoing trials during the control block.

Figure 3

A. Psychophysiological Interaction (PPI) effects between right middle temporal gyrus (62 −12 −16) and precuneus (−2 −72 40) and the left aPFC. B. The precuneus shows stronger left aPFC connectivity in the Nonfocal condition, but greater PM transient activity in the Focal condition. C. The right temporal cortex (TC) shows stronger left aPFC connectivity in the Focal condition, and also stronger PM transient activity in this condition as well. PM: transient effect on PM trials (correct trials only); Ong-PM: transient effect for category decision task trials (ongoing trials) during the PM block; Ong- CTL: transient effect for ongoing trials during the control block.

Figure 3

A. Psychophysiological Interaction (PPI) effects between right middle temporal gyrus (62 −12 −16) and precuneus (−2 −72 40) and the left aPFC. B. The precuneus shows stronger left aPFC connectivity in the Nonfocal condition, but greater PM transient activity in the Focal condition. C. The right temporal cortex (TC) shows stronger left aPFC connectivity in the Focal condition, and also stronger PM transient activity in this condition as well. PM: transient effect on PM trials (correct trials only); Ong-PM: transient effect for category decision task trials (ongoing trials) during the PM block; Ong- CTL: transient effect for ongoing trials during the control block.