The influence of perceptual similarity and individual differences on false memories in aging

Age-related reduction in anxiety and neural encoding of negative emotional memory

Introduction

Older adults experience less anxiety. We examined how memory of negative emotional images varied with age and may reflect age-related differences in anxiety.

Methods

Fifty-one adults, age 22-80 years, underwent imaging with a memory task where negative and neutral images were displayed pseudo-randomly. They were queried post-scan about the images inter-mixed with an equal number of images never displayed. Sensitivity (d') and reporting bias (Z-score of false alarm rate; Z[FAR]) were quantified with signal detection theory.

Results

Age was negatively correlated with both Spielberg State Trait Anxiety Inventory (STAI) state score and d' (negative - neutral) and positively with Z[FAR] (negative - neutral). However, STAI score and d' or Z[FAR] (negative - neutral) were not significantly correlated. In whole-brain regression, STAI score was correlated with higher activity of the right middle/superior temporal gyri/temporal parietal junction (MTG/STG/TPJ) for "negative correct - incorrect" - "neutral correct - incorrect" trials. Further, the MTG/STG/TPJ activity (β) was also negatively correlated with age. Mediation analyses supported a complete mediation model of age → less anxiety → less MTG/STG/TPJ β.

Discussion

Together, the findings demonstrated age-related changes in negative emotional memory and how age-related reduction in anxiety is reflected in diminished temporoparietal cortical activities during encoding of negative emotional memory.

Investigating the neural basis of schematic false memories by examining schematic and lure pattern similarity

ABSTRACTSchemas allow us to make assumptions about the world based upon previous experiences and aid in memory organisation and retrieval. However, a reliance on schemas may also result in increased false memories to schematically related lures. Prior neuroimaging work has linked schematic processing in memory tasks to activity in prefrontal, visual, and temporal regions. Yet, it is unclear what type of processing in these regions underlies memory errors. The current study examined where schematic lures exhibit greater neural similarity to schematic targets, leading to this memory error, as compared to neural overlap with non-schematic lures, which, like schematic lures, are novel items at retrieval. Results showed that patterns of neural activity in ventromedial prefrontal cortex, medial frontal gyrus, middle temporal gyrus, hippocampus, and occipital cortices exhibited greater neural pattern similarity for schematic targets and schematic lures than between schematic lures and non-schematic lures. As such, results suggest that schematic membership, and not object history, may be more critical to the neural processes underlying memory retrieval in the context of a strong schema.

Investigating the neural basis of schematic false memories by examining schematic and lure pattern similarity

Schemas allow us to make assumptions about the world based upon previous experiences and aid in memory organization and retrieval. However, a reliance on schemas may also result in increased false memories to schematically related lures. Prior neuroimaging work has linked schematic processing in memory tasks to activity in prefrontal, visual, and temporal regions. Yet, it is unclear what type of processing in these regions underlies memory errors. The current study examined where schematic lures exhibit greater neural similarity to schematic targets, leading to this memory error, as compared to neural overlap with non-schematic lures, which, like schematic lures, are novel items at retrieval. Results showed that patterns of neural activity in ventromedial prefrontal cortex, medial frontal gyrus, middle temporal gyrus, hippocampus, and occipital cortices exhibited greater neural pattern similarity for schematic targets and schematic lures than between schematic lures and non-schematic lures. As such, results suggest that schematic membership, and not object history, may be more critical to the neural processes underlying memory retrieval in the context of a strong schema.

The effect of visual perspective on episodic memory in aging: A virtual reality study

The possibility of flexibly retrieving our memories using a first-person or a third-person perspective (1PP or 3PP) has been extensively investigated in episodic memory research. Here, we used a Virtual Reality-based paradigm to manipulate the visual perspective used during the encoding stage to investigate age-related differences in the formation of memories experienced from 1PP vs. 3PP. 32 young adults and 32 seniors participated in the study. Participants navigated through two virtual cities to encode complex real-life virtual events, from either a 1PP (as if from their egocentric viewpoint) or a 3PP, while actively controlling an avatar. While recognition accuracy was higher in young adults after encoding in 1PP compared to 3PP, there was no benefit in memory formation in 1PP for older adults. These findings are discussed in terms of both age-related changes in episodic memory functioning and self-referencing processes.

Within-category similarity negatively affects associative memory performance in both younger and older adults

Associative memory involves the ability to encode and remember the relationship between individual items. This ability can become diminished when there is a high degree of similarity between stimuli that are being learned. Associative memory errors often stem from the fact that lures include a high degree of item familiarity as well as mnemonic similarity with the original associative episode. The current set of experiments examined how this overlap, in the form of within-category similarity, affects veridical and false retrieval in both younger and older adults. Across three experiments, results suggest that mnemonic overlap between targets and lures is detrimental to the ability to discriminate between highly similar information. Specifically, shared category membership for targets and lures led to increased false associative memories across age groups. These results have implications for scenarios where there is a high degree of overlap between target and lure events and indicate that these types of associative memory distinctions are difficult irrespective of age.

Understanding associative false memories in aging using multivariate analyses

Age-related declines in associative memory are ubiquitous, with decreases in behavioral discriminability largely arising from increases in false memories for recombined lures. Using representational similarity analyses to examine the neural basis of associative false memories in aging, the current study found that neural pattern similarity between Hits and FAs and Hits and CRs differed as a function of age in occipital ROIs, such that older adults exhibited a smaller difference between the two similarity metrics than did younger adults. Additionally, greater Hit-FA representational similarity correlated with increases in associative FAs across several ROIs. Results suggest that while neural representations underlying targets may not differ across ages, greater pattern similarity between the neural representation of targets and lures may reflect reduced distinctiveness of the information encoded in memory, such that old and new items are more difficult to discriminate, leading to more false alarms.

Effect of aging differs for memory of object identity and object position within a spatial context

There has been considerable focus on investigating age-related memory changes in cognitively healthy older adults, in the absence of neurodegenerative disorders. Previous studies have reported age-related domain-specific changes in older adults, showing increased difficulty encoding and processing object information but minimal to no impairment in processing spatial information compared with younger adults. However, few of these studies have examined age-related changes in the encoding of concurrently presented object and spatial stimuli, specifically the integration of both spatial and nonspatial (object) information. To more closely resemble real-life memory encoding and the integration of both spatial and nonspatial information, the current study developed a new experimental paradigm with novel environments that allowed for the placement of different objects in different positions within the environment. The results show that older adults have decreased performance in recognizing changes of the object position within the spatial context but no significant differences in recognizing changes in the identity of the object within the spatial context compared with younger adults. These findings suggest there may be potential age-related differences in the mechanisms underlying the representations of complex environments and furthermore, the integration of spatial and nonspatial information may be differentially processed relative to independent and isolated representations of object and spatial information.

The production of false recognition and the associated state of consciousness following encoding in a naturalistic context in aging

Using virtual reality, we implemented a naturalistic variant of the DRM paradigm in young and older adults to evaluate false recall and false recognition. We distinguished false recognition related to the highest semantic association (the critical lures), semantic similarity (i.e. items that belong to the same semantic category), and perceptual similarity (i.e. items that are similar, but not identical in terms of shape or color). The data revealed that younger adults recalled and recognized more correct elements than older adults did while the older adults intruded more critical items than younger adults. Both age groups produced false recognition related to the critical items, followed by perceptually and then semantically related items. False recognitions were highly recollective as they were mainly associated with a sense of remembering, even more so in older adults than in young adults. The decline of executive functions and working memory predicted age-related increases in false memories.

Differentiating True and False Schematic Memories in Older Adults

OBJECTIVE

While schemas aid memory for schematically related information, the gist induced by the schema can also lead to high rates of false memories, especially in older adults. The neural mechanisms that support and differentiate true and false memories in aging are not well understood. The current study sought to clarify this, using a novel scene paradigm to investigate the role of schemas on true and false memories in older adults.

METHODS

Healthy older adults encoded schematic scenes (e.g., bathroom). At retrieval, participants were tested on their memory for both schematic and nonschematic targets and lures while functional magnetic resonance imaging data was collected.

RESULTS

Results indicate that true memories were supported by the typical retrieval network, and activity in this network was greater for true than false memories. Schema specific retrieval was supported by medial prefrontal cortex, extending this common finding to aging. While no region differentiated false memories compared to correct rejections, results showed that individual differences in false memory rates were associated with variability in neural activity.

DISCUSSION

The findings underscore the importance of elucidating the neural basis of cognition within older adults, as well as the specific contribution of individual differences to the neural basis of memory errors in aging.

Recognition memory shielded from semantic but not perceptual interference in normal aging

Normal aging impairs long-term declarative memory, and evidence suggests that this impairment may be driven partly by structural or functional changes in the medial temporal lobe (MTL). Theories of MTL memory function therefore make predictions for age-related memory loss. One theory - the Representational-Hierarchical account - makes two specific predictions. First, recognition memory performance in older participants should be impaired by feature-level interference, in which studied items contain many shared, and thus repeatedly appearing, perceptual features. Second, if the interference in a recognition memory task - i.e., the information that repeats across items - resides at a higher level of complexity than simple perceptual features, such as semantic gist, older adults should be less impacted by such interference than young adults. We tested these predictions using the Deese-Roediger-McDermott paradigm, by creating feature-level (i.e., perceptual) interference with phonemically/orthographically related word categories, and higher-level associative interference with semantically related word categories. We manipulated category size in order to compare the effect of less versus more interference (i.e., small versus large category size), which served to (1) avoid potential item confounds arising from systematic differences between words belonging to perceptually- versus semantically-related categories, and (2) ensure that any effect of interference was due to information encoded at study, rather than pre-experimentally. Further, we used signal detection theory (SDT) to interpret our data, rather than examining false alarm (FA) rates in isolation. The d' measure derived from SDT avoids contamination of the memory measure by response bias, and lies on an interval scale, allowing memory performance in different conditions to be compared without violating assumptions of the statistical tests. Older participants were relatively more impaired by perceptual interference and less impaired by semantic interference than young adults. This pattern is at odds with many current theories of age-related memory loss, but is in line with the Representational-Hierarchical account.