Declarative Memory

ABSTRACT— Neuroimaging of declarative memory is not an endeavor divorced from psychology but, instead, is another path through which a more complete understanding of memory has emerged. Specifically, neuroimaging allows us to determine if differences between memory states emerge from quantitatively or qualitatively distinct underlying encoding operations. Further, it has allowed for greater specification of the putative control operations adopted when we make decisions about our memories. We describe some examples of insights provided by neuroimaging into the many and varied processes that support encoding and retrieval of declarative memory.     

PET studies of encoding and retrieval: The HERA model

We review positron emission tomography (PET) studies whose results converge on the hemispheric encoding/retrieval asymmetry (HERA) model of the involvement of prefrontal cortical regions in the processes of human memory. The model holds that the left prefrontal cortex is differentially more involved in retrieval of information from semantic memory, and in simultaneously encoding novel aspects of the retrieved information into episodic memory, than is the right prefrontal cortex. The right prefrontal cortex, on the other hand, is differentially more involved in episodic memory retrieval than is the left prefrontal cortex. This general pattern holds for different kinds of information (e.g., verbal materials, pictures, faces) and a variety of conditions of encoding and retrieval.     

Neuroanatomical correlates of implicit and explicit memory for structurally possible and impossible visual objects

Implicit memory refers to nonconscious retrieval of past experience demonstrated by facilitation in test performance on tasks that do not require intentional recollection of previous experiences. Explicit memory, in contrast, refers to the conscious retrieval of prior information, as demonstrated during standard recall and recognition tasks. In this experiment, positron emission tomographic (PET) measurements of regional cerebral blood flow (CBF), a marker of local neuronal activity, were used to identify and contrast brain regions that participate in the perception, implicit memory, and explicit memory for structurally possible and impossible visual objects. Ten CBF images were acquired in 16 normal women as they made possible/impossible and old/new recognition decisions about previously studied (old) and nonstudied (new) structurally possible and impossible objects. As reported previously, object decisions for familiar possible objects were associated with increased CBF in the vicinity of the left inferior temporal and fusiform gyri and recognition memory for familiar possible objects was associated with increased CBF in the vicinity of the right hippocampus. In this report, we provide more extensive analyses of the roles of the inferior temporal cortex, the hippocampus, the parahippocampus, and the pulvinar in encoding and retrieval operations. Additionally, patterns of CBF increases and decreases provide information regarding the neural structures involved in implicit and explicit memory.     

Contributions of the medial temporal lobe to declarative memory retrieval: manipulating the amount of contextual retrieval

We investigated how the hippocampus and its adjacent mediotemporal structures contribute to contextual and noncontextual declarative memory retrieval by manipulating the amount of contextual information across two levels of the same contextual dimension in a source memory task. A first analysis identified medial temporal lobe (MTL) substructures mediating either contextual or noncontextual retrieval. A linearly weighted analysis elucidated which MTL substructures show a gradually increasing neural activity, depending on the amount of contextual information retrieved. A hippocampal engagement was found during both levels of source memory but not during item memory retrieval. The anterior MTL including the perirhinal cortex was only engaged during item memory retrieval by an activity decrease. Only the posterior parahippocampal cortex showed an activation increasing with the amount of contextual information retrieved. If one assumes a roughly linear relationship between the blood-oxygenation level-dependent (BOLD) signal and the associated cognitive process, our results suggest that the posterior parahippocampal cortex is involved in contextual retrieval on the basis of memory strength while the hippocampus processes representations of item-context binding. The anterior MTL including perirhinal cortex seems to be particularly engaged in familiarity-based item recognition. If one assumes departure from linearity, however, our results can also be explained by one-dimensional modulation of memory strength.     

Behavioral functions of the CA3 subregion of the hippocampus

From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, one-trial short-term or working memory, and one-trial cued recall primarily for spatial information. These are tasks that have been assumed to reflect the operations of episodic memory and require interactions between CA3a,b and the dentate gyrus via mossy fiber inputs into the CA3a,b. The CA3a,b is also important for encoding of spatial information requiring multiple trials including the acquisition of arbitrary and relational associations. These tasks tend to be non-episodic and can be mediated by arbitrary and conjunctive operations. All these tasks are assumed to operate within an autoassociative network function of the CA3 region. The output from CA3a,b via the fimbria and the medial and lateral perforant path inputs play a supporting role in the neural circuit that supports the operation of these tasks. The CA3a,b also plays a role in sequential processing of information in cooperation with CA1 based on the Schaffer collateral output from CA3a,b to CA1. The CA3a,b also supports retrieval of short-term memory information based on a spatial pattern completion process. Finally, CA3c may, in cooperation with the dentate gyrus, serve an important role in processing the geometry of the environment.     

Memory for faces: Encoding and retrieval operations

The reliable finding that trait judgments of faces yield better recognition memory than do feature judgments of faces is conceptualized as an encoding-specificity effect. Specifically, both trait-judgment encodings of faces and face-recognition tests are argued to be holistic, involving topographical information with between-feature processing. Consistent with the concept that encoding and retrieval operations interact to produce retrieval success, it was expected that a memory-for-face test using the Identi-kit (which requires reconstructions of the face at a feature level of analysis) would show trait-encoding tasks to be inferior to feature-encoding tasks. Eighty subjects were assigned randomly to judge a face on 10 trait dimensions (e.g., honesty-dishonesty) or on 10 feature dimensions (e.g., narrow nose-wide nose) and subsequently attempted to recognize the target among five distractors or to reconstruct the face from an Identi-kit. The significant interaction between encoding and retrieval operations indicated that the face was best identified under trait-encoding conditions but best reconstructed under feature-encoding conditions. The match between trait encoding and recognition in yielding high memory performance suggests strongly that trait judgments foster holistic processing of faces (i.e., interfeature topographical information is p-art of the context) and that the recognition of faces also is holistic. Finally, the utility of the feature- vs. holistic-processing distinction is questioned, and an alternative is proposed.     

Regional and inter-regional theta oscillation during episodic novelty processing

Recent event-related potential (ERP) and functional magnetic resonance imaging (fMRI) studies suggest that novelty processing may be involved in processes that recognize the meaning of a novel sound, during which widespread cortical regions including the right prefrontal cortex are engaged. However, it remains unclear how those cortical regions are functionally integrated during novelty processing. Because theta oscillation has been assumed to have a crucial role in memory operations, we examined local and inter-regional neural synchrony of theta band activity during novelty processing. Fifteen right-handed healthy university students participated in this study. Subjects performed an auditory novelty oddball task that consisted of the random sequence of three types of stimuli such as a target (1000 Hz pure tone), novel (familiar environmental sounds such as dog bark, buzz, car crashing sound and so on), and standard sounds (950 Hz pure tone). Event-related spectra perturbation (ERSP) and the phase-locking value (PLV) were measured from human scalp EEG during task. Non-parametric statistical tests were applied to test for significant differences between stimulus novelty and stimulus targets in ERSP and PLV. The novelty P3 showed significant higher amplitude and shorter latency compared with target P3 in frontocentral regions. Overall, theta activity was significantly higher in the novel stimuli compared with the target stimuli. Specifically, the difference in theta power between novel and target stimuli was most significant in the right frontal region. This right frontal theta activity was accompanied by phase synchronization with the left temporal region. Our results imply that theta phase synchronization between right frontal and left temporal regions underlie the retrieval of memory traces for unexpected but familiar sounds from long term memory in addition to working memory retrieval or novelty encoding.     

Active hippocampus during nonconscious memories

The hippocampal formation is known for its importance in conscious, declarative memory. Here, we report neuroimaging evidence in humans for an additional role of the hippocampal formation in nonconscious memory. We maskedly presented combinations of faces and written professions such that subjects were not aware of them. Nevertheless, the masked presentations activated many of the brain regions that unmasked presentations of these stimuli did. To induce a nonconscious retrieval of the faces and face-associated occupational information, subjects were instructed to view the previously masked faces and to guess the professional category of each person--academic, artist, and workman. Guessing the professional category of previously masked versus new faces activated the left and right hippocampal formation and right perirhinal cortex as well as bilateral fusiform areas and fronto-temporal areas known to mediate the retrieval of semantic information. These activations within the semantic processing system suggest that conceptual knowledge acquired during masking was nonconsciously retrieved. Our data provide clues to an analogous role of the hippocampus in conscious and nonconscious memory.     

Effects of interpolated processing on experts’ recall of schematic information

The present study, using schematic sport diagrams, examined the perceptual chunking hypothesis (Chase & Simon, 1973a; 1973b) that visual patterns are represented by labels in a limited-capacity, short-term memory. This study, which employed three subject-skill levels and an interpolated processing paradigm, indicated that for experts, information extracted during an 8-second study period has great longevity and durability. Interpolated processing demands, along with an additional encoding activity of a second diagram presentation, had minimal effects on recall performance. This evidence supports the position that meaningful and familiar information abstracted during a brief exposure period is immediately processed in long-term memory, thus facilitating subsequent retrieval.     

Brands on the brain: Do consumers use declarative information or experienced emotions to evaluate brands?

An fMRI study was conducted with unfamiliar and familiar (strong and weak) brands to assess linguistic encoding and retrieval processes, and the use of declarative and experiential information, in brand evaluations. As expected, activations in brain areas associated with linguistic encoding were higher for unfamiliar brands, but activations in brain areas associated with information retrieval were higher for strong brands. Interestingly, weak brands were engaged simultaneously in both processes. Most importantly, activations of the pallidum, associated with positive emotions, for strong brands and activations of the insula, associated with negative emotions, for weak and unfamiliar brands suggested that consumers use experienced emotions rather than declarative information to evaluate brands. As a result, brand experiences should be considered a key driver of brand equity in addition to brand awareness and cognitive associations.     

编码如何预测提取?以相继记忆效应为证

在记忆领域, 编码与提取之间的关系始终备受关注。近37年(1980至今)的研究显示, 随后记住信息与随后遗忘信息在编码阶段关联的神经机制明显不同(该差异被称为相继记忆效应), 表明编码能够从神经机制角度预测提取。过去10年间(2008~2017), 研究者在顺承先前研究的基础上另辟蹊径, 重点从编码任务中加工水平及目标导向对相继记忆效应的影响、提取任务对相继记忆效应的影响、不同年龄群体之间的相继记忆效应异同、情绪项目和情绪背景对相继记忆效应的影响等角度展开研究。本文从上述四方面对相关研究进行了详细梳理, 并从整合研究成果、完善理论模型、挖掘潜在社会因素、探究个体差异和群体差异以及加强应用推广等方面对今后研究进行展望。     

The posterior parietal cortex and long-term memory representation of spatial information

The hypothesis to be explored in this chapter is based on the assumption that the posterior parietal cortex (PPC) is directly involved in representing a subset of the spatial features associated with spatial information processing and plays an important role in perceptual memory as well as long-term memory encoding, consolidation, and retrieval of spatial information. After presentation of the anatomical location of the PPC in rats, the nature of PPC representation based on single spatial features, binding of visual features associated with visual spatial attention, binding of object-place associations associated with acquisition and storage of associations where one of the elements is a spatial component, and binding of ideothetic and allothetic information in long-term memory is discussed. Additional evidence for a PPC role in mediation of spatial information in long-term storage is offered. Finally, the relationship between the PPC and the hippocampus from a systems and dynamic point view is presented.     

Modulation of retrieval processing reflects accuracy of emotional source memory

There is considerable evidence that encoding and consolidation of memory are modulated by emotion, but the retrieval of emotional memories is not well characterized. Here we manipulated the emotional context with which affectively neutral stimuli were associated during encoding, allowing us to examine neural activity associated with retrieval of emotional memories without confounding the emotional attributes of cue items and the retrieved context. Using a source memory procedure we were also able to compare how retrieval processing was modulated when the emotional encoding context was recollected or not. An interaction between emotional encoding context and accuracy of source memory revealed that successful retrieval of emotional context was associated with activity in left amygdala, and a left frontotemporal network including anterior insula, prefrontal cortex and cingulate. In contrast, when contextual retrieval was unsuccessful, items encoded in emotional contexts elicited enhanced activity in right amygdala and a right-lateralized network that included extrastriate visual areas. These findings indicate distinct effects of emotion on successful and unsuccessful retrieval of source information, including lateralization of amygdala responses.     

Remembering the past and imagining the future: a neural model of spatial memory and imagery

The authors model the neural mechanisms underlying spatial cognition, integrating neuronal systems and behavioral data, and address the relationships between long-term memory, short-term memory, and imagery, and between egocentric and allocentric and visual and ideothetic representations. Long-term spatial memory is modeled as attractor dynamics within medial-temporal allocentric representations, and short-term memory is modeled as egocentric parietal representations driven by perception, retrieval, and imagery and modulated by directed attention. Both encoding and retrieval/imagery require translation between egocentric and allocentric representations, which are mediated by posterior parietal and retrosplenial areas and the use of head direction representations in Papez's circuit. Thus, the hippocampus effectively indexes information by real or imagined location, whereas Papez's circuit translates to imagery or from perception according to the direction of view. Modulation of this translation by motor efference allows spatial updating of representations, whereas prefrontal simulated motor efference allows mental exploration. The alternating temporal-parietal flows of information are organized by the theta rhythm. Simulations demonstrate the retrieval and updating of familiar spatial scenes, hemispatial neglect in memory, and the effects on hippocampal place cell firing of lesioned head direction representations and of conflicting visual and ideothetic inputs.     

Variations in constrained retrieval

Mentally reinstating encoding operations at retrieval might improve access to memories; however, such constrained retrieval is an effortful process that may not always be used. The memory-for-foils procedure (Jacoby, Shimizu, Daniels, & Rhodes, Psychonomic Bulletin & Review 12, 852-857, 2005) infers participant-initiated mental reinstatement of encoding operations during attempts at recognition from the differential memory that accrues to foils during a test of deeply processed items versus during a test of shallowly processed items, as indicated by performance on a final recognition memory test for the foils. Experiment 1 tested whether differential memory for foils is due to the evocation of task context during recollection of neighboring old items. Experiment 2 tested whether inducing a set to respond without much effort on a prior recognition test affects the likelihood of constrained retrieval on later tests. Experiment 3 tested whether constrained retrieval is less likely to occur when the deep versus shallow source of test items is intermixed, rather than blocked in separate tests. These experiments provide evidence that people query memory by mentally reinstating encoding operations and identify conditions that affect the probability of constrained retrieval.     

Patterns of brain-electrical activity during declarative memory performance in 10-month-old infants

This study of infant declarative memory concurrently examined brain-electrical activity and deferred imitation performance in 10-month-old infants. Continuous electroencephalogram (EEG) measures were collected throughout the activity-matched baseline, encoding (modeling) and retrieval (delayed test) phases of a within-subjects deferred imitation task. Infants were divided into two memory performance groups based on the exhibition of ordered-recall after a 24-h delay. Whereas no group differences were found in EEG collected during encoding, performance-group differences in EEG were present during retrieval. Infants who successfully displayed ordered-recall showed a pattern of increasing EEG from baseline to task at anterior temporal scalp locations, whereas infants showing no ordered-recall displayed no changes in EEG from baseline to task. These findings are discussed with respect to the biobehavioral developments underlying declarative memory abilities.     

Patterns of brain-electrical activity during declarative memory performance in 10-month-old infants

This study of infant declarative memory concurrently examined brain-electrical activity and deferred imitation performance in 10-month-old infants. Continuous electroencephalogram (EEG) measures were collected throughout the activity-matched baseline, encoding (modeling) and retrieval (delayed test) phases of a within-subjects deferred imitation task. Infants were divided into two memory performance groups based on the exhibition of ordered-recall after a 24-h delay. Whereas no group differences were found in EEG collected during encoding, performance-group differences in EEG were present during retrieval. Infants who successfully displayed ordered-recall showed a pattern of increasing EEG from baseline to task at anterior temporal scalp locations, whereas infants showing no ordered-recall displayed no changes in EEG from baseline to task. These findings are discussed with respect to the biobehavioral developments underlying declarative memory abilities.     

When the mask falls: The role of facial motor resonance in memory for emotional language

The recognition and interpretation of emotional information (e.g., about happiness) has been shown to elicit, amongst other bodily reactions, spontaneous facial expressions occurring in accordance to the relevant emotion (e.g. a smile). Theories of embodied cognition act on the assumption that such embodied simulations are not only an accessorial, but a crucial factor in the processing of emotional information. While several studies have confirmed the importance of facial motor resonance during the initial recognition of emotional information, its role at later stages of processing, such as during memory for emotional content, remains unexplored. The present study bridges this gap by exploring the impact of facial motor resonance on the retrieval of emotional stimuli. In a novel approach, the specific effects of embodied simulations were investigated at different stages of emotional memory processing (during encoding and/or retrieval). Eighty participants underwent a memory task involving emotional and neutral words consisting of an encoding and retrieval phase. Depending on the experimental condition, facial muscles were blocked by a hardening facial mask either during encoding, during retrieval, during both encoding and retrieval, or were left free to resonate (control). The results demonstrate that not only initial recognition but also memory of emotional items benefits from embodied simulations occurring during their encoding and retrieval.     

Effects of selective perirhinal and postrhinal lesions on acquisition and retention of a visual discrimination task in rats

The hippocampal region along with rhinal structures seems to support learning and memory in an important manner. Structures adjacent to the rhinal fissure in the rat have recently been suggested to be divided into the perirhinal and postrhinal cortices. Some effects of perirhinal lesions on cognitive processing are known, whereas effects of postrhinal lesions appear to be unknown. The purpose of the present study was to examine the relative effects of perirhinal and postrhinal lesions in a three-choice visual discrimination test. The results show that both types of lesions impaired acquisition of the task, but only perirhinal lesions impeded subsequent retention. Because the initial phase of acquisition was unaffected by both lesions, it is suggested that the deficits observed may be of mnemonic nature. The apparent differential involvement of the perirhinal cortex and postrhinal cortex in cognition may be associated with differences in anatomical connectivity among these structures.