Memory Search Research Articles

Dynamic search and working memory in social recall.

What are the mechanisms underlying search in social memory (e.g., remembering the people one knows)? Do the search mechanisms involve dynamic local-to-global transitions similar to semantic search, and are these transitions governed by the general control of attention, associated with working memory span? To find out, we asked participants to recall individuals from their personal social networks and measured each participant's working memory capacity. Additionally, participants provided social-category and contact-frequency information about the recalled individuals as well as information about the social proximity among the recalled individuals. On the basis of these data, we tested various computational models of memory search regarding their ability to account for the patterns in which participants recalled from social memory. Although recall patterns showed clustering based on social categories, models assuming dynamic transitions between representations cued by social proximity and frequency information predicted participants' recall patterns best-no additional explanatory power was gained from social-category information. Moreover, individual differences in the time between transitions were positively correlated with differences in working memory capacity. These results highlight the role of social proximity in structuring social memory and elucidate the role of working memory for maintaining search criteria during search within that structure.

How does memory search interact with the attentional blink

How does memory search interact with the attentional blink

P-1246 - Functional specificities of semantic memory between early-onset-schizophrenia and autism spectrum disorder: quantitative and qualitative analyses of verbal fluency task

Adolescents with early-onset-schizophrenia (EOS) and with autism spectrum disorder (ASD) exhibit similar cognitive impairments which may be related to different neurocognitive processes. The present study aimed to compare the semantic memory structure and function in adolescents with EOS and ASD in order to highlight some fundamental similarity or distinctions between the two disorders. Adolescents with EOS (n = 16), with ASD (n = 14) and with typical development (n = 24) matched on general, verbal and performance IQ, participated to a verbal fluency task. A quantitative analysis (number of words correctly reported) was made in letter and category fluency task. Qualitative analysis (number of clusters and switches and cluster size) was made using the CFT. The semantic memory structure was derived from a multidimensional scaling analysis (MDS) using sequential word outputs from the CFT. Adolescents with EOS and with ASD exhibited performance reduction compared to control group. EOS and ASD exhibited similar quantitative performance and produced similar number of clusters on CFT. In contrast, qualitative analysis showed that EOS produced more switches and smaller cluster size compared to ASD. MDS analysis of the semantic memory structure revealed atypical associations of category members in EOS compared to ASD and to healthy adolescents. Despite quantitatively similar results, EOS and ASD appear to use different sematic strategies of memory search which may results from qualitative differences of the functional organization of the semantic memory. Semantic memory disorganization appear to be specific to schizophrenia and may be a considered as specific marker to the disorder.

Unravelling Difference

ABSTRACTThis article interrogates the possibility of developing a “sensory multiculture,” in which difference could be encountered outside of domination or appropriation. It invokes alternative dialogic aesthetic practices for living with difference. The article centers on the film Unravelling (2008, dir. Kuldip Powar and produced as part of the Noise of the Past project). This film is shown to offer a fragile and speculative practice of “counter-memory” and “fabulation” for re-telling the story of post-colonial migrant involvement in the Second World War. At the heart of the film is the search for migrant experiences and memories of war that cannot be simply recuperated for buttressing nationhood. The film is replete with archival footage of war, multi-layered visual imagery, dialogic poetic exchange and an evocative textured soundscape. It is argued that the film creates an alter-realist aesthetic liberated from regimes of truth and racialized objectification of migrant life. The sensory multicultural aesthetic which the film activates effectively disrupts official histories of war and memory and offers an alternative mode of post-colonial belonging.

Memory-based Decision-making with Heuristics: Evidence for a Controlled Activation of Memory Representations

Many of our daily decisions are memory based, that is, the attribute information about the decision alternatives has to be recalled. Behavioral studies suggest that for such decisions we often use simple strategies (heuristics) that rely on controlled and limited information search. It is assumed that these heuristics simplify decision-making by activating long-term memory representations of only those attributes that are necessary for the decision. However, from behavioral studies alone, it is unclear whether using heuristics is indeed associated with limited memory search. The present study tested this assumption by monitoring the activation of specific long-term-memory representations with fMRI while participants made memory-based decisions using the "take-the-best" heuristic. For different decision trials, different numbers and types of information had to be retrieved and processed. The attributes consisted of visual information known to be represented in different parts of the posterior cortex. We found that the amount of information required for a decision was mirrored by a parametric activation of the dorsolateral PFC. Such a parametric pattern was also observed in all posterior areas, suggesting that activation was not limited to those attributes required for a decision. However, the posterior increases were systematically modulated by the relative importance of the information for making a decision. These findings suggest that memory-based decision-making is mediated by the dorsolateral PFC, which selectively controls posterior storage areas. In addition, the systematic modulations of the posterior activations indicate a selective boosting of activation of decision-relevant attributes.

Orienting attention to locations in mental representations

Many cognitive processes depend on our ability to hold information in mind, often well beyond the offset of the original sensory input. The capacity of this visual short-term memory (VSTM) is limited to around three to four items. Recent research has demonstrated that the content of VSTM can be modulated by top-down attentional biases. This has been demonstrated using retrodictive spatial cues, termed "retro-cues," which orient subjects' attention to spatial locations within VSTM. In the present article, we tested whether the use of these cues is modulated by memory load and cue delay. There are a number of important conclusions: (1) Top-down biases can operate on very brief iconic traces as well as on older VSTM representations (Exp. 1). (2) When operating within capacity, subjects use the cue to prioritise where they initiate their memory search, rather than to discard uncued items (Exps. 2 and 3). (3) When capacity is exceeded, there is little benefit to top-down biasing relative to a neutral condition; however, unattended items are lost, with there being a substantial cost of invalid spatial cueing (Exp. 3). (4) These costs and benefits of orienting spatial attention differ across iconic memory and VSTM representations when VSTM capacity is exceeded (Exp. 4).

Searching for robust quantum memories in many coupled oscillators

The relation between microscopic symmetries in the system-environment interaction and the emergence of robust states is studied for many linearly coupled harmonic oscillators. Different types of symmetry, which are introduced into the model as terms in the coupling constants between each systemʼs oscillator and a common reservoir, lead to distinct robust modes. Since these modes are partially or completely immune to the symmetric part of the environmental noise, they are good candidates for building quantum memories. A comparison of the model investigated here, with bilinear system-reservoir coupling, and a model where such coupling presents an exponential dependence on the variables of interest is performed.

Associative information in memory: Evidence from cued recall

The representation of item and associative information in episodic memory was investigated using cued recall and single item recognition. In the first four experiments, participants studied two lists constructed such that some items presented in a pair during List 1 were rearranged to create new pairs in List 2 and were accompanied by pairs exclusive to List 2. List 1 was composed of either word–face pairs (Experiment 1 and 3) or word–word and face–face pairs (Experiment 2 and 4). Participants were tested for their memory of the second list containing only word-face pairs. When the test required associative information (i.e., cued recall), interference was specific to pair-type. Specifically, repeating items in the same pair-type across lists led to a greater number of correct and incorrect responses but repeating items in different pair-types did not change performance. When the test did not require associative information (i.e., single item recognition), interference was not specific to pair-type; hits and false alarms were higher for items presented on List 1. In the final experiment, the number of studied pairs and single items was independently manipulated and a pair-specific list length effect was observed. That is, performance in cued recall was modulated by the number of studied pairs, but not the number of studied individual items. Together, these data suggest that information specific to the pair-type (i.e., associative information) is stored and strategically utilized during memory search.

The neural dynamics of task context in free recall

Multivariate pattern analysis (MVPA) is a powerful tool for relating theories of cognitive function to the neural dynamics observed while people engage in cognitive tasks. Here, we use the Context Maintenance and Retrieval model of free recall (CMR; Polyn et al., 2009a) to interpret variability in the strength of task-specific patterns of distributed neural activity as participants study and recall lists of words. The CMR model describes how temporal and source-related (here, encoding task) information combine in a contextual representation that is responsible for guiding memory search. Each studied word in the free-recall paradigm is associated with one of two encoding tasks (size and animacy) that have distinct neural representations during encoding. We find evidence for the context retrieval hypothesis central to the CMR model: Task-specific patterns of neural activity are reactivated during memory search, as the participant recalls an item previously associated with a particular task. Furthermore, we find that the fidelity of these task representations during study is related to task-shifting, the serial position of the studied item, and variability in the magnitude of the recency effect across participants. The CMR model suggests that these effects may be related to a central parameter of the model that controls the rate that an internal contextual representation integrates information from the surrounding environment.

Heuristic Search for Large Problems With Real Costs

The memory requirements of basic best-first heuristic search algorithms like A* make them infeasible for solving large problems. External disk storage is cheap and plentiful com- pared to the cost of internal RAM. Unfortunately, state-of- the-art external memory search algorithms either rely on brute-force search techniques, such as breadth-first search, or they rely on all node values falling in a narrow range of in- tegers, and thus perform poorly on real-world domains with real-valued costs. We present a new general-purpose algo- rithm, PEDAL, that uses external memory and parallelism to perform a best-first heuristic search capable of solving large problems with real costs. We show theoretically that PEDAL is I/O efficient and empirically that it is both better on a stan- dard unit-cost benchmark, surpassing internal IDA* on the 15-puzzle, and gives far superior performance on problems with real costs.

The neural correlates of specific versus general autobiographical memory construction and elaboration

We examined the neural correlates of specific (i.e., unique to time and place) and general (i.e., extended in or repeated over time) autobiographical memories (AMs) during their initial construction and later elaboration phases. The construction and elaboration of specific and general events engaged a widely distributed set of regions previously associated with AM recall. Specific (vs. general) event construction preferentially engaged prefrontal and medial temporal lobe regions known to be critical for memory search and retrieval processes. General event elaboration was differentiated from specific event elaboration by extensive right-lateralized prefrontal cortex (PFC) activity. Interaction analyses confirmed that PFC activity was disproportionately engaged by specific AMs during construction, and general AMs during elaboration; a similar pattern was evident in regions of the left lateral temporal lobe. These neural differences between specific and general AM construction and elaboration were largely unrelated to reported differences in the level of detail recalled about each type of event.

De-Biasing the Age-Happiness Bias: Memory Search and Cultural Expectations in Happiness Judgments Across the Lifespan

While most research shows increasing happiness across the adult life-span, there is a common and persistent misconception that happiness decreases with age. In two experiments, we found evidence to suggest that this age-happiness bias results in part from a biased search for exemplars in memory. When provided with specific exemplars, aged 30 or 70, showing clear evidence of an active and sociable lifestyle, happiness estimates were unaffected by age. However, we also found evidence that the bias may influence judgments by invoking different standards for young and old. Among participants in the United States in Experiment 1, a negative lifestyle description resulted in negative happiness ratings for a 30 year-old and neutral ratings for a 70 year-old, suggesting that the lifestyle was considered normative for the older adults. Among Irish participants in Experiment 2, we found no such distinction, arguably because of cultural differences in social expectations across the generations. These studies help to reveal the judgment mechanisms behind the age-happiness bias, and identify the boundaries of this persistent bias.

Oscillatory patterns in temporal lobe reveal context reinstatement during memory search

Psychological theories of memory posit that when people recall a past event, they not only recover the features of the event itself, but also recover information associated with other events that occurred nearby in time. The events surrounding a target event, and the thoughts they evoke, may be considered to represent a context for the target event, helping to distinguish that event from similar events experienced at different times. The ability to reinstate this contextual information during memory search has been considered a hallmark of episodic, or event-based, memory. We sought to determine whether context reinstatement may be observed in electrical signals recorded from the human brain during episodic recall. Analyzing electrocorticographic recordings taken as 69 neurosurgical patients studied and recalled lists of words, we uncovered a neural signature of context reinstatement. Upon recalling a studied item, we found that the recorded patterns of brain activity were not only similar to the patterns observed when the item was studied, but were also similar to the patterns observed during study of neighboring list items, with similarity decreasing reliably with positional distance. The degree to which individual patients displayed this neural signature of context reinstatement was correlated with their tendency to recall neighboring list items successively. These effects were particularly strong in temporal lobe recordings. Our findings show that recalling a past event evokes a neural signature of the temporal context in which the event occurred, thus pointing to a neural basis for episodic memory.

Eye movements as a gatekeeper for memorization: evidence for the persistence of attentional sets in visual memory search

Attention is known to serve multiple goals, including the selection of information for further perceptual analysis (selection for perception) and for goal-directed behavior (selection for action). Here, we study the role of overt attention (i.e., eye movements) as a gatekeeper for memorization processes (selection for memorization). Subjects memorized complex multidimensional stimulus displays and subsequently indicated whether a specific (probe) item was present. In Experiment 1 we utilized an incidental learning setting where in the beginning only a subset of display stimuli was relevant, whereas in a transfer block all stimuli were possible probe items. In Experiment 2, we used an explicit learning setting within a between-group design. Response times and gaze patterns indicated that subjects learned to ignore irrelevant stimuli while forming memory representations. The findings suggest that complex feature binding processes in peripheral vision may serve to guide overt selective attention, which eventually contributes to filtering out irrelevant information even in highly complex environments. Gaze patterns suggested that attentional control settings persisted even when they were no longer required.

Life story chapters, specific memories and the reminiscence bump

Theories of autobiographical memory posit that extended time periods (here termed chapters) and memories are organised hierarchically. If chapters organise memories and guide their recall, then chapters and memories should show similar temporal distributions over the life course. Previous research demonstrates that positive but not negative memories show a reminiscence bump and that memories cluster at the beginning of extended time periods. The current study tested the hypotheses that (1) ages marking the beginning of positive but not negative chapters produce a bump, and that (2) specific memories are over-represented at the beginning of chapters. Potential connections between chapters and the cultural life script are also examined. Adult participants first divided their life story into chapters and identified their most positive and most negative chapter. They then recalled a specific memory from both their most positive and most negative chapter. As predicted, the beginning age of positive but not negative chapters produced a bump and specific memories tended to cluster at chapter beginnings. The results support the idea that chapters guide the search for specific memories and that the cultural life script contributes to the search process.

Abordagem histórica de uma mata destinada a conservação ambiental no município de Dourados-MS

A Educação Ambiental é fundamental no processo de conscientização dos seres humanos sobre a necessidade de mudança de hábitos, tanto individuais como coletivos, e na busca de soluções para amenizar os problemas ambientais. Este estudo, realizado no Centro Educacional e Social Marista (CESMAR), localizado na Comunidade João Paulo II, na cidade de Dourados no Estado do Mato Grosso do Sul, buscou diagnosticar a percepção em relação aos aspectos culturais e de consciência ecológica. Através do resgate da memória histórica da comunidade local, analisou-se a contribuição dos Irmãos Maristas para a proteção da mata na área pesquisada. A partir da abordagem quanti-qualitativa com entrevista semi-estruturada e questionários, envolvendo pessoas da comunidade e educandos do CESMAR, analisamos os problemas identificados na área estudada.

The reminiscence bump for salient personal memories: Is a cultural life script required?

Older adults report a higher frequency of autobiographical memories for experiences that occurred between ages 15 and 30, as compared with other life periods. This reminiscence bump is evident for memories involving positive, but not negative, emotions. The cultural life script hypothesis proposes that people share knowledge for the types and timing of positive landmark events and that this script guides the memory search to the bump period. The present research examined whether a reminiscence bump would be evident when memory cues prompted recall of surprising and unexpected events. Older adults recalled positive and negative, surprising positive and surprising negative, or highly expected and highly unexpected events. Adults' memory distributions were compared with distributions of predicted life events generated by undergraduates. Reminiscence bumps were found not only for memories of positive and expected events, but also for memories of surprising and unexpected events. Implications for the life script account are discussed.

Five down, Absquatulated: Crossword puzzle clues to how the mind works

Doing crossword puzzles is a popular pastime; no one knows how many people do them, but estimates go as high as 50 million or more in the United States alone. Success at crossword puzzles taxes several aspects of memory and cognition. The purpose of this article is to consider hints that crosswords provide and questions that they prompt regarding how the mind works. Implicated topics include word associations, lexical memory search, semantic priming, the sparseness of word space, list generation, the feeling of knowing and of not knowing, mental aging, and the crossword puzzle as a vehicle for studying cognition.

Lifespan changes in multi-tasking: Concurrent walking and memory search in children, young, and older adults

We investigated dual-task performance of cognitive (semantic fluency) and sensorimotor tasks (walking) in 120 children and adults from four age groups (9-year olds, M = 9.52 years; 11-year olds, M = 11.51 years; young adults, M = 25.34 years; older adults, M = 64.28 years; N = 30 per group). Distances walked during 90 s and numbers of category exemplars generated in the semantic fluency task showed an inverted U-shape function with age. In line with general resource models proportional dual-task costs in walking also showed a U-shaped relation as a function of age with pronounced decrements in the youngest and oldest groups. Only 9-year olds showed significant costs in the cognitive task. Individual differences in single-task performance accounted for more than half of the variance in dual-task performance. Reliable age-related residual variance implicated additional factors particularly in children's developing multi-tasking performances.

Search-Related Suppression of Hippocampus and Default Network Activity during Associative Memory Retrieval

Episodic memory retrieval involves the coordinated interaction of several cognitive processing stages such as mental search, access to a memory store, associative re-encoding, and post-retrieval monitoring. The neural response during memory retrieval is an integration of signals from multiple regions that may subserve supportive cognitive control, attention, sensory association, encoding, or working memory functions. It is particularly challenging to dissociate contributions of these distinct components to brain responses in regions such as the hippocampus, which lies at the interface between overlapping memory encoding and retrieval, and “default” networks. In the present study, event-related functional magnetic resonance imaging (fMRI) and measures of memory performance were used to differentiate brain responses to memory search from subcomponents of episodic memory retrieval associated with successful recall. During the attempted retrieval of both poorly and strongly remembered word pair associates, the hemodynamic response was negatively deflected below baseline in anterior hippocampus and regions of the default network. Activations in anterior hippocampus were functionally distinct from those in posterior hippocampus and negatively correlated with response times. Thus, relative to the pre-stimulus period, the hippocampus shows reduced activity during intensive engagement in episodic memory search. Such deactivation was most salient during trials that engaged only pre-retrieval search processes in the absence of successful recollection or post-retrieval processing. Implications for interpretation of hippocampal fMRI responses during retrieval are discussed. A model is presented to interpret such activations as representing modulation of encoding-related activity, rather than retrieval-related activity. Engagement in intensive mental search may reduce neural and attentional resources that are otherwise tonically devoted to encoding an individual’s stream of experience into episodic memory.