Associative Recall Research Articles

Associative Memories With Synaptic Delays.

In this paper, we introduce a new concept of associative memories in which synaptic connections of the self-organizing neural network learn time delays between input sequence elements. Synaptic connections represent both the synaptic weights and expected delays between the network inputs. This property of synaptic connections facilitates recognition of time sequences and provides context-based associations between sequence elements. Characteristics of time delays are learned and are updated each time an input sequence is presented. There are no separate learning and testing modes typically used in other neural networks, as the network starts to predict the next input element as soon as there is no expected input signal. The network generates output signals useful for associative recall and prediction. These output signals depend on the presented input context and the knowledge stored in the graph. Such a mode of operation is preferred for the organization of episodic memories used to store the observed episodes and to recall them if a sufficient context is provided. The associative sequential recall is useful for the operation of working memory in a cognitive agent. Test results demonstrate that the network correctly recognizes the input sequences with variable delays and that it is more efficient than other recently developed sequential memory networks based on associative neurons.

Novel Face-Name Paired Associate Learning and Famous Face Recognition in Mild Cognitive Impairment: A Neuropsychological and Brain Volumetric Study

Purpose: To assess visual associative learning and famous face recognition ability among subjects with stable amnestic mild cognitive impairment (MCI) relative to early stage dementia due to Alzheimer’s disease (AD) and cognitively normal healthy controls (NC) and to correlate these differences with volumetric changes on MRI. Methods: A hospital-based cross-sectional observational study was conducted on 61 participants. The subjects underwent neuropsychological evaluation, including validated newly designed tests for novel face-name paired association learning recall and famous face recognition. MRI volumetry was done on a subset of patients to ascertain the topographical patterns of volume loss. Results: There were significant differences in performance on free recall for face-name paired associate learning in MCI (n = 22) compared to NC (n = 20) (p < 0.001) and MCI compared to AD (n = 19; p < 0.001). Significant differences were also noted in scores on the famous personalities test between MCI and NC (p = 0.007), and MCI and AD (p = 0.032). The free recall component of face-name pair associative learning significantly correlated with left cuneus (p = 0.005; r = 0.833) and right cuneus (p = 0.003; r = 0.861) volume in AD with no significant correlation among MCI and NC cohorts. Conclusions: Novel and semantically familiar face-name associative recalls are significantly impaired in MCI, and these potentially predate the MRI volumetric changes in MCI. Our findings expand the spectrum of recall deficits in MCI.

The picture superiority effect in associative memory: A developmental study.

We tested whether semantic relatedness between to-be-remembered items and item presentation format (pictorial vs. verbal) affects associative recall. Fifty-nine children (11-13years old) and forty young adults (age 18-30) completed a learning and recall task for semantically related (e.g., padlock-key) and unrelated (e.g., lemon-piano) picture-picture, word-picture, and word-word pairs. The data revealed memory advantage for semantically related item pairs, and for pictures compared to words. A picture superiority effect was found exclusively for pure picture pairs. Despite pronounced differences in memory accuracy, the effect of semantic relatedness and the picture superiority effect were comparable in adults and children. Semantic relatedness and pictures seem to trigger deeper semantic processing of associated items. Our results suggest distinct contributions of semantic binding and memory strategies to associative memory, while the last seem to account particularly for age-related differences in associative recall. Statement of contribution What is already known on this subject? Recognition advantage for picture over word stimuli, known as the picture superiority effect. PSE is found for single and associated picture over word items. Conflicting data about developmental aspects of the PSE. What does this study add? PSE is modulated by pre-existing semantic relations between picture stimuli. Semantic relation seems to modulate the PSE to a lesser extent in children than in adults. The cognitive processes behind the PSE might change with age.

Recall cues interfere with retrieval from visuospatial working memory.

Visuospatial working memory allows us to hold multiple visual objects over short delays. It is typically tested by presenting an array of objects, then after a delay showing a ‘probe’ indicating which memory item to recall or reproduce by adjusting a target feature. However, recent studies demonstrate that information at the time of probe can disrupt recall. Here, in three experiments we test whether traditional memory probes, which contain features that compete with the feature to be recalled, may themselves interfere with performance. We asked participants to report the direction of one of the several coloured arrows in memory, based on its colour. First, we demonstrate that recall is better when the probe is initially just a coloured dot, rather than a coloured arrow which has to be adjusted to match orientation memory, consistent with interference from features of the probe itself. Second, this interference is present even when a mask follows the memory array, suggesting that the interference does not work by degrading immediate or iconic memory. Finally, when items are shown sequentially, the first and last items are invulnerable to probe interference. Our findings support recent theories of associative recall, in which probes reactivate features in WM, retrieving information by pattern completion.

Associative Memory and Belief Formation

This paper experimentally studies the role of associative memory for belief formation. Real-world information signals are often embedded in memorable contexts. Thus, today's news, and the contexts they are embedded in, may cue the selective retrieval of similar past news and hence contribute to the widely documented pattern of expectation overreaction. Based on a stylized version of models of associative memory in the literature, we develop a simple and tightly controlled experimental setup in which participants observe sequences of news about the stock market value of hypothetical companies. Here, identical types of news are associated with identical stories and images. In this setup, participants' expectations strongly overreact to recent news. We successfully verify the model's predictions about how the magnitude of overreaction should depend on the history of news. For example, once today's news are associated with the stories and images of previous opposite news, expectations systematically under-react. By exogenously manipulating the scope for imperfect and associative recall in our setup, we further provide direct causal evidence for the role of memory in belief formation and overreaction. Finally, we use our experimental data to estimate the model parameters that govern the strength of imperfect and associative recall over different time horizons.

Modeling Contextual Modulation of Memory Associations in the Hippocampus.

We present a computational model of how memories can be contextually acquired and recalled in the hippocampus. Our adaptive contextual memory model comprises the lateral entorhinal cortex (LEC), the dentate gyrus (DG) and areas CA3 and CA1 in the hippocampus, and assumes external inputs about context that originate in the prefrontal cortex (PFC). Specifically, we propose that there is a top-down bias on the excitability of cells in the DG of the hippocampus that recruits a sub-population of cells to differentiate contexts, independent of experienced stimuli, expanding the “pattern separation” role typically attributed to the DG. It has been demonstrated in rats that if PFC is inactivated, both acquisition and recall of memory associations are impaired. However, PFC inactivation during acquisition of one set of memory associations surprisingly leads to subsequent facilitation of the acquisition of a conflicting set of memory associations in the same context under normal PFC operation. We provide here the first computational and algorithmic account of how the absence or presence of the top-down contextual biases on the excitability of DG cells during different learning phases of these experiments explains these data. Our model simulates PFC inactivation as the loss of inhibitory control on DG, which leads to full or partial activation of DG cells related to conflicting memory associations previously acquired in different contexts. This causes context-inappropriate memory traces to become active in the CA3 recurrent network and thereby the output CA1 area within the hippocampus. We show that these incongruous memory patterns proactively interfere with and slow the acquisition of new memory associations. Further, we demonstrate that pattern completion within CA3 in response to a partial cue for the recall of previously acquired memories is also impaired by PFC inactivation for the same reason. Pre-training the model with interfering memories in contexts different from those used in the experiments, simulating a lifetime of experiences, was crucial to reproduce the rat behavioral data. Finally, we made several testable predictions based on the model that suggest future experiments to deepen our understanding of brain-wide memory processes.

Hippocampal activations in mesial temporal lobe epilepsy due to hippocampal sclerosis- an observational study on intramural encoding-delayed recall paradigms using task-based memory fMRI

ObjectivesTo validate concurrent utility of within-scanner encoding and delayed recognition-memory paradigms to ascertain hippocampal activations during task-based memory fMRI. MethodsMemory paradigms were designed for faces, word-pairs and abstract designs. A deep-encoding task was designed comprising of a total of 9 cycles run within a 1.5T MRI scanner. A recall session was performed after 1 h within the scanner using an event-related design. Group analysis was done with ‘correct-incorrect' responses applied as parametric modulators in Statistical Parametric Mapping version 8 using boot-strap method to enable estimation of laterality indices (LI) using custom anatomical masks involving the medio-basal temporal structures. ResultsTwenty seven subjects with drug-resistant mesial temporal lobe epilepsy due to hippocampal sclerosis (MTLE-HS) [17 patients of left-MTLE and 10 patients of right-MTLE] and 21 right handed age-matched healthy controls (HC) were recruited. For the encoding paradigm blood oxygen level dependent (BOLD) responses in HC demonstrated right laterality for faces, left laterality for word pairs, and bilaterality for design encoding over the regions of interest. Both right and left MTLE-HS groups revealed left lateralisation for word-pair encoding, bilateral activation for face encoding, with design encoding in right MTLE-HS demonstrating a left shift. As opposed to lateralization shown in controls, group analysis of cued-recall BOLD signals acquired within scanner in left MTLE-HS demonstrated right lateralization for word-pairs with bilaterality for faces and designs. The right MTLE-HS group demonstrated bilateral activations for faces, word-pairs and designs. ConclusionRecall-based fMRI paradigms indicate hippocampal plasticity in MTLE-HS, maximal for word-pair associate recall tasks.

Visual associations to retrieve episodic memory across healthy elderly, mild cognitive impairment, and patients with Alzheimer’s disease

ABSTRACTEpisodic memory tests need to determine the degree to which patients with moderate to severe memory deficits can still benefit from retrieval support. Especially in the case of Alzheimer’s disease (AD), this may support health care to be more closely aligned with patients’ memory capacities. We investigated whether the different measures of episodic memory of the Visual Association Test-Extended (VAT-E) can provide a more detailed and informative assessment on memory disturbances across a broad range of cognitive decline, from normal to severe impairment as seen in AD, by examining differences in floor effects. The VAT-E consists of 24 pairs of black-and-white line drawings. In a within-group design, we compared score distributions of VAT-E subtests in healthy elderly controls, mild cognitive impairment (MCI), and AD (n = 144), as well as in relation to global cognitive impairment. Paired associate recall showed a floor effect in 41% of MCI patients and 62% of AD patients. Free recall showed a floor effect in 73% of MCI patients and 84% of AD patients. Multiple-choice cued recognition did not show a floor effect in either of the patient groups. We conclude that the VAT-E covers a broad range of episodic memory decline in patients. As expected, paired associate recall was of intermediate difficulty, free recall was most difficult, and multiple-choice cued recognition was least difficult for patients. These varying levels of difficulty enable a more accurate determination of the level of retrieval support that can still benefit patients across a broad range of cognitive decline.

Episodic traces and statistical regularities: Paired associate learning in typical and dyslexic readers

Learning visual-phonological associations is a key skill underlying successful reading acquisition. However, we are yet to understand the cognitive mechanisms that enable efficient learning in good readers, and those which are aberrant in individuals with developmental dyslexia. Here, we use a repeated cued-recall task to examine how typical and reading-impaired adults acquire novel associations between visual and phonological stimuli, incorporating a looking-at-nothing paradigm to probe implicit memory for target locations. Cued recall accuracy revealed that typical readers’ recall of novel phonological associates was better than dyslexic readers’ recall, and it also improved more with repetition. Eye fixation-contingent error analyses suggest that typical readers’ greater improvement from repetition reflects their more robust encoding and/or retrieval of each instance in which a given pair was presented: whereas dyslexic readers tended to recall a phonological target better when fixating its most recent location, typical readers showed this pattern more strongly when the target location was consistent across multiple trials. Thus, typical readers’ greater success in reading acquisition may derive from their better use of statistical contingencies to identify consistent stimulus features across multiple exposures. We discuss these findings in relation to the role of implicit memory in forming new visual-phonological associations as a foundational skill in reading, and areas of weakness in developmental dyslexia.

Inactivation of the Ventrolateral Orbitofrontal Cortex Impairs Flexible Use of Safety Signals

Survival depends on adaptation to shifting environmental risks and opportunities. Regarding risks, the mechanisms which permit acquisition, recall, and flexible use of aversive associations is poorly understood. Drawing on the evidence that the orbital frontal cortex is critical to integrating outcome expectancies with flexible appetitive behavioral responses, we hypothesized that OFC would contribute to behavioral flexibility within an aversive learning domain. We introduce a fear conditioning procedure in which adult male rats were presented with shock-paired conditioned stimulus (CS+) or a safety cue (CS−). In a recall test, rats exhibit greater freezing to the CS+ than the CS−. Temporary inactivation of the ventrolateral OFC with muscimol prior to conditioning did not affect later discrimination, but inactivation after learning and prior to recall impaired discrimination between safety and danger cues. This result complements prior research in the appetitive domain and suggests that the OFC plays a general role in behavioral flexibility regardless of the valence of the CS.

The Neural Bases of Interoceptive Encoding and Recall in Healthy Adults and Adults With Depression

BackgroundTheoretical models assert that the brain’s interoceptive network links external stimuli with their interoceptive consequences, thereby supporting later recall of these associations to guide the selection of healthy behaviors. If these accounts are correct, previously reported interoceptive abnormalities in major depressive disorder (MDD) should lead to altered recall of associations between external stimuli and their interoceptive (somatic) consequences. To date, the processes underlying interoceptive recall have never been experimentally investigated. MethodsWe designed and implemented the Interoceptive Encoding and Recall task to compare interoceptive and exteroceptive recall among subjects with MDD (n = 24) and healthy comparison subjects (n = 21). During the encoding phase, subjects learned to pair neutral visual cues (geometric shapes) with aversive interoceptive and exteroceptive stimuli. Later, while undergoing functional magnetic resonance imaging, subjects were prompted to recall the stimulus associated with each shape. ResultsInteroceptive recall, relative to exteroceptive recall, was associated with bilateral mid-to-posterior insula activation. Relative to the healthy control participants, participants with depression exhibited marked hypoactivation of the right dorsal mid-insula during interoceptive recall. ConclusionsIn healthy control subjects, simply recalling a stimulus associated with a previous interoceptive challenge activated a key region in the brain’s interoceptive network. Although previous research has linked MDD with aberrant processing of interoceptive stimuli, the current study is the first to demonstrate that individuals with MDD exhibit decreased insula activity while recalling interoceptive memories. It is possible that insula hypoactivation during interoceptive recall may affect the representation of prior interoceptive experiences in ways that contribute to depressive symptomology and the relationship between depression and systemic health.

Dynamic Neural Turing Machine with Continuous and Discrete Addressing Schemes.

We extend the neural Turing machine (NTM) model into a dynamic neural Turing machine (D-NTM) by introducing trainable address vectors. This addressing scheme maintains for each memory cell two separate vectors, content and address vectors. This allows the D-NTM to learn a wide variety of location-based addressing strategies, including both linear and nonlinear ones. We implement the D-NTM with both continuous and discrete read and write mechanisms. We investigate the mechanisms and effects of learning to read and write into a memory through experiments on Facebook bAbI tasks using both a feedforward and GRU controller. We provide extensive analysis of our model and compare different variations of neural Turing machines on this task. We show that our model outperforms long short-term memory and NTM variants. We provide further experimental results on the sequential [Formula: see text]MNIST, Stanford Natural Language Inference, associative recall, and copy tasks.

The Testing Effect is Preserved in Stressful Final Testing Environment

SummaryPrevious studies have shown that retrieval practice leads to better long‐term memory than additional study of a material (a phenomenon termed the testing effect). In this study, we compared the effectiveness of these learning strategies when the final test occurs under stress (such as in an exam). Participants studied word pairs; then half of the material was repeatedly studied, whereas the other half was repeatedly tested. Following a 7‐day delay, participants were exposed to either a psychosocially stressful situation or a control task, followed by an associative recall task that tested memory for all items. Multiple measures were used to assess stress levels: emotional state assessments as well as assays of salivary cortisol and alpha‐amylase levels. Results are in favour of the ecological validity of retrieval‐based learning. Participants recalled more retested items than restudied items regardless of being exposed to a stressful situation and the hormonal (cortisol) response to stress. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Age differences in coupling of intraindividual variability in mnemonic strategies and practice-related associative recall improvements.

The importance of encoding strategies for associative recall is well established, but there have been no studies of aging and intraindividual variability (IAV) in strategy use during extended practice. We observed strategy use and cued-recall test performance over 101 days of practice in 101 younger adults (M = 25.6 years) and 103 older adults (M = 71.3 years) sandwiched by a pretest and posttest battery including an associative recall test. Each practice session included 2 lists of 12 number-noun paired-associate (PA) items (e.g., 23-DOGS), presented for brief exposures titrated to maintain below-ceiling performance throughout practice. Participants reported strategy use (e.g., rote repetition, imagery) after each test. Substantial IAV in strategy use was detected that was coupled with performance; lists studied with normatively effective strategies (e.g., imagery) generated higher PA recall than lists studied with less effective strategies (e.g., rote repetition). In comparison to younger adults, older adults' practice (a) relied more on repetition and less on effective strategies, (b) showed lower levels of IAV in effective strategy use, and (c) had lower within-person strategy-recall coupling, especially late in practice. Individual differences in pretest-posttest gains in PA recall were predicted by average level of effective strategy use in young adults but by strategy-recall coupling in older adults. Results are consistent with the hypothesis that experiencing variability in strategic outcomes during practice helps hone the effectiveness of strategic encoding behavior, and that older adults' reduced degree of pretest-posttest gains is influenced by lower likelihood of using and optimizing effective strategies through practice. (PsycINFO Database Record

Verbalization and musical memory in string players

The purpose of this study was to examine the effect of verbalization about a brief etude on collegiate string players’ short- and long-term recall of the etude in question. We examined competing hypotheses that suggest it is possible that verbalization (i.e., verbal analysis of musical features) (a) could aid in recall both by highlighting patterns and constraints that inform the music’s creation and by facilitating the creation of explicit performance cues that help to bridge gaps between associative recall chains or (b) may hinder recall by interfering with the creation of procedural and auditory memories necessary for musical performance. Participants ( N = 20) were assigned to experimental conditions in which they learned an unfamiliar etude either through repetition alone or through repetition followed by the completion of a verbalization worksheet provided by the experimenter. Recall was tested both immediately following initial practice and 24 hours later to examine the effect of verbalization on both short- and long-term retention. Findings indicated no differences between groups on immediate recall performance but significant differences at the 24-hour recall task with participants in the verbalization condition recalling more material. In addition, the patterns of errors found across groups indicated a strong primacy effect. Theoretical implications for the study of memory processes in musical contexts and practical implications regarding the preparation of memorized performance are discussed.

P302 Right parietal tDCS and object-location memory

Background Memory enhancement is one of the most challenging issues in neurorehabilitation. Memory functions are affected by different neurological conditions as well as by normal aging. Recent data suggest that it may be possible to improve performance on some of the memory tests by physiological modulation of the activity within a neural loop which plays crucial role in formation and maintenance of the associative memory, the main parts of which are the hippocampus and the lateral parietal cortex. Aim To examine whether anodal transcranial direct current stimulation (tDCS) over right parietal cortex would have an effect on associative memory between objects and locations. Methods Ten healthy right-handed participants (5 male, age 20–28) were enrolled in a cross-over placebo-controlled study. We applied 20-min anodal or sham tDCS of 1.5 mA over the P4 site of 10–20 EEG system, and participants completed a object-location test immediately after, as well as 24 h, and 7 days after stimulation. Object-location test consisted of recognition and recall task. Results For recall task the repeated measures ANOVA showed significant main effect of stimulation ( F ( 1 , 9 ) = 6.32 , p . 05 , η 2 = . 41 ), main effect of time ( F ( 2 , 18 ) = 3.48 , p = . 05 , η 2 = . 28 ), as well as interaction effect ( F ( 2 , 18 ) = 4.57 , p . 05 , η 2 = . 34 ). On the other hand no significant effects were observed on recognition task. Conclusions The results indicate that single tDCS session over parietal cortex has a potential to improve delayed recall of object-location associations.

Multiple-object Tracking as a Tool for Parametrically Modulating Memory Reactivation.

Converging evidence supports the "nonmonotonic plasticity" hypothesis, which states that although complete retrieval may strengthen memories, partial retrieval weakens them. Yet, the classic experimental paradigms used to study effects of partial retrieval are not ideally suited to doing so, because they lack the parametric control needed to ensure that the memory is activated to the appropriate degree (i.e., that there is some retrieval but not enough to cause memory strengthening). Here, we present a novel procedure designed to accommodate this need. After participants learned a list of word-scene associates, they completed a cued mental visualization task that was combined with a multiple-object tracking (MOT) procedure, which we selected for its ability to interfere with mental visualization in a parametrically adjustable way (by varying the number of MOT targets). We also used fMRI data to successfully train an "associative recall" classifier for use in this task: This classifier revealed greater memory reactivation during trials in which associative memories were cued while participants tracked one, rather than five, MOT targets. However, the classifier was insensitive to task difficulty when recall was not taking place, suggesting that it had indeed tracked memory reactivation rather than task difficulty per se. Consistent with the classifier findings, participants' introspective ratings of visualization vividness were modulated by MOT task difficulty. In addition, we observed reduced classifier output and slowing of responses in a postreactivation memory test, consistent with the hypothesis that partial reactivation, induced by MOT, weakened memory. These results serve as a "proof of concept" that MOT can be used to parametrically modulate memory retrieval-a property that may prove useful in future investigation of partial retrieval effects, for example, in closed-loop experiments.

Cognitive deficits in the first 24 hours after the onset of first unprovoked generalized Tonic and clonic seizure

BackgroundMany people with epilepsy suffer from cognitive deficits as a consequence of their seizure episodes. Relatively few researches have been undertaken to assess the short term impacts of seizure on cognitive function. This study aimed to evaluate changes in cognitive performance in adults with a new onset generalized seizure in the first 24h after the onset of their attack. MethodsAfter having given informed consent, 40 patients with first episode of unprovoked generalized tonic-clonic seizure were investigated with a neuropsychological test battery (Wechsler Memory Scale III). Their performance was compared with 40 healthy individuals from the patients' companions. ResultsNewly diagnosed patients had significantly worse performance in paired association recall which is a parameter of verbal memory; other memory parameters showed no significant changes after seizure attack. ConclusionOur data suggested that even with a one-time seizure episode, patients are susceptible to verbal memory impairment.

Position-element frequency learning is dissociable from Hebb repetition learning

Abstract Position-element association has been extensively investigated as a mechanism for serial order memory and has been widely implemented in models of short-term memory. This study examined whether and how the position-element association is learned as a form of long-term knowledge dissociated from other forms of knowledge such as sequence knowledge acquired in the Hebb list repetition paradigm. Laboratory learning experiments demonstrated that repeated exposure to a specific position-element association facilitated subsequent recall of the position-element association with experimental control of other aspects of to-be-learned statistical structure of the artificial phonotactics. The experiments also demonstrated that the positional frequency learning was more gradual than Hebb list learning, suggesting a dissociation of the two forms of learning. Functional roles of these two forms of learning were discussed.

How Does Associative Recall Shape the Process of Belief Formation?

How Does Associative Recall Shape the Process of Belief Formation?