Episodic memory processes modulate how schema knowledge is used in spatial memory decisions

Episodic memory and semantic knowledge interact to guide eye movements during visual search in scenes: Distinct effects of conscious and unconscious memory

Episodic memory and semantic knowledge can each exert strong influences on visual attention when we search through real-world scenes. However, there is debate surrounding how they interact when both are present; specifically, results conflict as to whether memory consistently improves visual search when semantic knowledge is available to guide search. These conflicting results could be driven by distinct effects of different types of episodic memory, but this possibility has not been examined. To test this, we tracked participants' eyes while they searched for objects in semantically congruent and incongruent locations within scenes during a study and test phase. In the test phase containing studied and new scenes, participants gave confidence-based recognition memory judgments that indexed different types of episodic memory (i.e., recollection, familiarity, unconscious memory) for the background scenes, then they searched for the target. We found that semantic knowledge consistently influenced both early and late eye movements, but the influence of memory depended on the type of memory involved. Recollection improved first saccade accuracy in terms of heading towards the target in both congruent and incongruent scenes. In contrast, unconscious memory gradually improved scanpath efficiency over the course of search, but only when semantic knowledge was relatively ineffective (i.e., incongruent scenes). Together, these findings indicate that episodic memory and semantic knowledge are rationally integrated to optimize attentional guidance, such that the most precise or effective forms of information available - which depends on the type of episodic memory available - are prioritized.

How schema knowledge influences memory in older adults: Filling in the gaps, or leading memory astray?

Age-related declines in episodic memory do not affect all types of mnemonic information equally: when to-be-remembered information is in line with one's prior knowledge, or schema-congruent, older adults often show no impairments. There are two major accounts of this effect: One proposes that schemas compensate for memory failures in aging, and the other proposes that schemas instead actively impair older adults' otherwise intact memory for incongruent information. However, the evidence thus far is inconclusive, likely due to methodological constraints in teasing apart these complex underlying dynamics. We developed a paradigm that separately examines the contributions of underlying memory and schema knowledge to a final memory decision, allowing these dynamics to be examined directly. In the present study, healthy older and younger adults first searched for target objects in congruent or incongruent locations within scenes. In a subsequent test, participants indicated where in each scene the target had been located previously, and provided confidence-based recognition memory judgments that indexed underlying memory, in terms of recollection and familiarity, for the background scenes. We found that age-related increases in schema effects on target location spatial recall were predicted and statistically mediated by age-related increases in underlying memory failures, specifically within recollection. We also found that, relative to younger adults, older adults had poorer spatial memory precision within recollected scenes but slightly better precision within familiar scenes-and age increases in schema bias were primarily exhibited within recollected scenes. Interestingly, however, there were also slight age-related increases in schema effects that could not be explained by memory deficits alone, outlining a role for active schema influences as well. Together, these findings support the account that age-related schema effects on memory are compensatory in that they are driven primarily by underlying memory failures, and further suggest that age-related deficits in memory precision may also drive schema effects.

A reduction in self-reported confidence accompanies the recall of memories distorted by prototypes

When we recall a past event, we reconstruct the event based on a combination of episodic details and semantic knowledge (e.g., prototypes). Though prototypes can impair the veracity of recall, it remains unclear whether we are metacognitively aware of the distortions they introduce. To address this, we conducted six experiments in which participants learned object-colour/object-location pairs and subsequently recalled the colour/location when cued with the object. Leveraging unsupervised machine learning algorithms, we extracted participant-specific prototypes and embedded responses in two-dimensional space to quantify prototype-based distortions in individual memory traces. Our findings reveal robust and conceptually replicable evidence to suggest that prototype-based distortion is accompanied by a reduction in self-reported confidence - an implicit measure of metacognitive awareness. Critically, we find evidence to suggest that it is prototype-based distortion of a memory trace that undermines confidence, rather than a lack of confidence biasing reconstruction towards the use of prototypes. Collectively, these findings suggest that we possess metacognitive awareness of distortions embedded in our memories.

Divergent thinking modulates interactions between episodic memory and schema knowledge: Controlled and spontaneous episodic retrieval processes

The ability to generate novel ideas, known as divergent thinking, depends on both semantic knowledge and episodic memory. Semantic knowledge and episodic memory are known to interact to support memory decisions, but how they may interact to support divergent thinking is unknown. Moreover, it is debated whether divergent thinking relies on spontaneous or controlled retrieval processes. We addressed these questions by examining whether divergent thinking ability relates to interactions between semantic knowledge and different episodic memory processes. Participants completed the alternate uses task of divergent thinking, and completed a memory task in which they searched for target objects in schema-congruent or schema-incongruent locations within scenes. In a subsequent test, participants indicated where in each scene the target object had been located previously (i.e., spatial accuracy test), and provided confidence-based recognition memory judgments that indexed distinct episodic memory processes (i.e., recollection, familiarity, and unconscious memory) for the scenes. We found that higher divergent thinking ability-specifically in terms of the number of ideas generated-was related to (1) more of a benefit from recollection (a controlled process) and unconscious memory (a spontaneous process) on spatial accuracy and (2) beneficial differences in how semantic knowledge was combined with recollection and unconscious memory to influence spatial accuracy. In contrast, there were no effects with respect to familiarity (a spontaneous process). These findings indicate that divergent thinking is related to both controlled and spontaneous memory processes, and suggest that divergent thinking is related to the ability to flexibly combine semantic knowledge with episodic memory.

Eye movements dissociate between perceiving, sensing, and unconscious change detection in scenes

Detecting visual changes can be based on perceiving, whereby one can identify a specific detail that has changed, on sensing, whereby one knows that there is a change but is unable to identify what changed, or on unconscious change detection, whereby one is unaware of any change even though the change influences one's behavior. Prior work has indicated that the processes underlying these different types of change detection are functionally and neurally distinct, but the attentional mechanisms that are related to these different types of change detection remain largely unknown. In the current experiment, we examined eye movements during a change detection task in globally manipulated scenes, and participants indicated their change detection confidence on a scale that allowed us to isolate perceiving, sensing, and unconscious change detection. For perceiving-based change detection, but not sensing-based or unconscious change detection, participants were more likely to preferentially revisit highly changed scene regions across the first and second presentation of the scene (i.e., resampling). This increase in resampling started within 250 ms of the test scene onset, suggesting that the effect began within the first two fixations. In addition, changed scenes were related to more clustered (i.e., less dispersed) eye movements than unchanged scenes, particularly when the subjects were highly confident that no change had occurred - providing evidence for change detection outside of conscious awareness. The results indicate that perceiving, sensing, and unconscious change detection responses are related to partially distinct patterns of eye movements.

Effects of Information Load on Schema and Episodic Memory Formation

The formation of semantic memories is assumed to result from the abstraction of general, schema-like knowledge across multiple experiences, while at the same time, episodic details from individual experiences are forgotten. Against this backdrop, our study examined the effects of information load (high vs. low) during encoding on the formation of episodic and schema memory using an elaborated version of an object-place recognition (OPR) task in rats. The task allowed for the abstraction of a spatial rule across four (low information load) or eight (high information load) encoding episodes (spaced apart by a 20 min interval) in which the rats could freely explore two objects in an open field arena. After this encoding phase, animals were left undisturbed for 24 h and then tested either for the expression of schema memory, i.e., for the spatial rule, or memory for an individual encoding episode. Rats in the high information load condition exhibited a more robust schema memory for the spatial rule than in the low information load condition. In contrast, rats in the low load condition showed more robust memory for individual learning episodes than in the high information load condition. Our findings of opposing effects might point to an information-load-dependent competitive relationship between processes of schema and episodic memory formation, although other explanations are possible.