The formation of source memory under distraction

Abstract

Background: It is vital to select and process relevant information while restraining irrelevant information for successful retrieval. When multiple streams of information are concurrently present, the ability to overcome distraction is very crucial for processing relevant information. Despite its significance, the neural mechanism of successful memory formation under distraction remains unclear, especially with memory for associations. The present fMRI study investigated the effect of distraction due to irrelevant stimuli in source memory.

Methods: In the MR scanner, participants studied an item and perceptual context with no distractor, a letter-distractor, or a word-distractor. Following the study phase, a source recognition test was administered in which participants were instructed to judge the study status of the test items and context of studied items. Participants' encoding activity was back-sorted by later source recognition to find the influence of distractors in subsequent memory effects.

Results: Source memory with distractors recruited greater encoding activity in the left dorsolateral prefrontal cortex, and the bilateral inferior temporal gyrus/fusiform cortex, along with the left posterior hippocampus. However, enhanced activity in the left anterior ventrolateral prefrontal cortex and the left parahippocampal cortex predicted successful source memory regardless of the presence of a distractor.

Conclusions: These findings of subsequent memory effects suggest that strong binding of the item-context associations, as well as resistance to interference, may have greater premium in the formation of successful source memory of pictures under distraction. Further, attentional selection to the relevant target seems to play a major role in contextual binding under distraction by enhancing the viability of memory representations from interference effects of distractors.

Figure 1

Brain regions showing the effect of distraction in source memory formation (Sc: source correct, Si: source incorrect, ND: no-distractor, D: distractor). *p < .05. Error bars depict standard errors of the mean difference across participants.

Figure 2

The effect of distractors in source memory formation in ROI regions (Sc: source correct, Si: source incorrect, ND: no-distractor, D: distractor). *p < .001. Error bars depict standard errors of the mean difference across participants.