Implicit Memory Research Articles

The role of nondeclarative memory in the skill for language: Evidence from syntactic priming in patients with amnesia

Syntactic priming, the phenomenon in which participants adopt the linguistic behaviour of their partner, is widely used in psycholinguistics to investigate syntactic operations. Although the phenomenon of syntactic priming is well documented, the memory system that supports the retention of this syntactic information long enough to influence future utterances, is not as widely investigated. We aim to shed light on this issue by assessing patients with Korsakoff's amnesia on an active-passive syntactic priming task and compare their performance to controls matched in age, education, and premorbid intelligence. Patients with Korsakoff's syndrome display deficits in all subdomains of declarative memory, yet their nondeclarative memory remains intact, making them an ideal patient group to determine which memory system supports syntactic priming. In line with the hypothesis that syntactic priming relies on nondeclarative memory, the patient group shows strong priming tendencies (12.6% passive structure repetition). Our healthy control group did not show a priming tendency, presumably due to cognitive interference between declarative and nondeclarative memory. We discuss the results in relation to amnesia, aging, and compensatory mechanisms.

Single crystalline SrTiO3 as memristive model system: From materials science to neurological and psychological functions

Taking the advantage of the well-established defect chemistry of SrTiO3, acceptor and donor doped SrTiO3 single crystals are used as model systems to understand the roles of oxygen vacancies and the Schottky barrier in the resistive switching. More importantly, SrTiO3 based memristive devices are used to emulate the neurological and psychological functions of the brain. The synaptic plasticity is achieved with Ni/Nb-SrTiO3/Ti memristive devices, and the learning and forgetting processes of the brain, together with the resultant explicit and implicit memories, are also realized with the device. Associative learning, a classical learning case of the brain, is demonstrated as well. The emulation of various neurological and psychological functions in a single memristive device simplifies the construction of the artificial neural network and facilitates the advent of the artificial intelligence. In this work, materials science becomes directly related to neurology and psychology.

How visual working memory contents influence priming of visual attention.

Recent evidence shows that when the contents of visual working memory overlap with targets and distractors in a pop-out search task, intertrial priming is inhibited (Kristjánsson, Sævarsson & Driver, Psychon Bull Rev 20(3):514-521, 2013, Experiment 2, Psychonomic Bulletin and Review). This may reflect an interesting interaction between implicit short-term memory-thought to underlie intertrial priming-and explicit visual working memory. Evidence from a non-pop-out search task suggests that it may specifically be holding distractors in visual working memory that disrupts intertrial priming (Cunningham & Egeth, Psychol Sci 27(4):476-485, 2016, Experiment 2, Psychological Science). We examined whether the inhibition of priming depends on whether feature values in visual working memory overlap with targets or distractors in the pop-out search, and we found that the inhibition of priming resulted from holding distractors in visual working memory. These results are consistent with separate mechanisms of target and distractor effects in intertrial priming, and support the notion that the impact of implicit short-term memory and explicit visual working memory can interact when each provides conflicting attentional signals.

Comparative functional neuroanatomy between implicit and explicit memory tasks under negative emotional condition in schizophrenia

PurposeTo evaluate the brain activation patterns in response to negative emotion during implicit and explicit memory in patients with schizophrenia. Material and methodsFourteen patients with schizophrenia and 14 healthy controls were included in this study. The 3.0T fMRI was obtained while the subjects performed the implicit and explicit retrievals with unpleasant words. ResultsThe different predominant brain activation areas were observed during the implicit retrieval and explicit with unpleasant words. ConclusionThe differential neural mechanisms between implicit and explicit memory tasks associated with negative emotional processing in schizophrenia.

Act Natural: Dubious Proposals in The Mill on the Floss, The Pastor’s Wife, Vera and Rebecca

Following George Eliot, Elizabeth von Arnim showcases a male rhetoric of naturalness. Her men cultivate and punish their women when they resist naturalizing. Without denigrating the intelligence of women, von Arnim shows their unwitting complicity in their subjection. In The Pastor’s Wife (1914) and in Vera (1921), the highly literate women have read the wrong books or missed the unfriendly truths about relationships in those they have read. The husbands and lovers make shallow use of philosophical and scientific reasoning to justify their control and enforce female uniformity deemed ‘natural’. Darwin is misappropriated by the tyrannical Wemyss: evolutionary theories support his imperious dismissal of Lucy’s aunt and friends. Wemyss’s most monstrous actions suggest an atavistic patriarchal dominance like the hereditary reversion theorized by Samuel Butler as unconscious memory. Wemyss brings up the issue of England’s inheritance, and a disturbing vision dawns as the philistine and self-appointed natural man subdues Lucy. Daphne du Maurier’s Rebecca (1938) follows Vera’s plot, but it does not interrogate naturalness in the same way. Entrapped in her husband’s vision of a natural woman, the narrator registers Rebecca’s wild transgressiveness as more powerful and universal than her own tamed naturalness.

Sleep-dependent consolidation of face recognition and its relationship to REM sleep duration, REM density and Stage 2 sleep spindles.

Face recognition is a highly specialized capability that has implicit and explicit memory components. Studies show that learning tasks with facial components are dependent on rapid eye movement and non-rapid eye movement sleep features, including rapid eye movement sleep density and fast sleep spindles. This study aimed to investigate the relationship between sleep-dependent consolidation of memory for faces and partial rapid eye movement sleep deprivation, rapid eye movement density, and fast and slow non-rapid eye movement sleep spindles. Fourteen healthy participants spent 1night each in the laboratory. Prior to bed they completed a virtual reality task in which they interacted with computer-generated characters. Half of the participants (REMD group) underwent a partial rapid eye movement sleep deprivation protocol and half (CTL group) had a normal amount of rapid eye movement sleep. Upon awakening, they completed a face recognition task that contained a mixture of previously encountered faces from the task and new faces. Rapid eye movement density and fast and slow sleep spindles were detected using in-house software. The REMD group performed worse than the CTL group on the face recognition task; however, rapid eye movement duration and rapid eye movement density were not related to task performance. Fast and slow sleep spindles showed differential relationships to task performance, with fast spindles being positively and slow spindles negatively correlated with face recognition. The results support the notion that rapid eye movement and non-rapid eye movement sleep characteristics play complementary roles in face memory consolidation. This study also raises the possibility that fast and slow spindles contribute in opposite ways to sleep-dependent memory consolidation.

Linking actions and objects: Context-specific learning of novel weight priors

Distinct explicit and implicit memory processes support weight predictions used when lifting objects and making perceptual judgments about weight, respectively. The first time that an object is encountered weight is predicted on the basis of learned associations, or priors, linking size and material to weight. A fundamental question is whether the brain maintains a single, global representation of priors, or multiple representations that can be updated in a context specific way. A second key question is whether the updating of priors, or the ability to scale lifting forces when repeatedly lifting unusually weighted objects requires focused attention. To investigate these questions we compared the adaptability of weight predictions used when lifting objects and judging their weights in different groups of participants who experienced size-weight inverted objects passively (with the objects placed on the hands) or actively (where participants lift the objects) under full or divided attention. To assess weight judgments we measured the size-weight illusion after every 20 trials of experience with the inverted objects both passively and actively. The attenuation of the illusion that arises when lifting inverted object was found to be context-specific such that the attenuation was larger when the mode of interaction with the inverted objects matched the method of assessment of the illusion. Dividing attention during interaction with the inverted objects had no effect on attenuation of the illusion, but did slow the rate at which lifting forces were scaled to the weight inverted objects. These findings suggest that the brain stores multiple representations of priors that are context specific, and that focused attention is important for scaling lifting forces, but not for updating weight predictions used when judging object weight.

Not all identification tasks are born equal: testing the involvement of production processes in perceptual identification and lexical decision.

The distinction between identification and production processes suggests that implicit memory should require more attention resources when there is a competition between alternative solutions during the test phase. The present two experiments assessed this hypothesis by examining the effects of divided attention (DA) at encoding on the high- and low-response-competition versions of perceptual identification (Experiment 1) and lexical decision (Experiment 2). In both experiments, words presented in the high-response-competition condition had many orthographic neighbours and at least one higher-frequency neighbour, whereas words presented in the low-response-competition condition had few orthographic neighbours and no higher-frequency neighbour. Consistent with the predictions of the identification/production distinction, Experiment 1 showed that DA reduced repetition priming in the high-, but not in the low-response-competition version of perceptual identification; in contrast, DA had comparable effects in the two versions of lexical decision (Experiments 2). These findings provide the first experimental evidence in support of the hypothesis that perceptual identification, a task nominally based on identification processes, might involve a substantive production component.

Priming recognition in good sleepers and in insomniacs.

Insomniacs often report memory and concentration problems, but these complaints have not been consistently supported by performance measurements. Furthermore, while the majority of studies have addressed explicit memory, few have investigated the implicit domain, and very little is known concerning other types of implicit memory besides procedural memory, such as priming. Thus, the purpose of the study was to investigate priming effect for visual stimuli in insomniacs and good sleepers. Twenty-three insomniacs and 20 good sleepers performed a visual priming task in which they were asked to name new and old pictures presented at nine ascending levels of spatial filtering. Both neutral and sleep-related stimuli were used, as previous research evidenced an attentional bias for sleep-related stimuli. Visual priming effect was observed in both groups, suggesting that poor sleep quality does not affect this type of implicit memory. However, the identification process in insomniacs is influenced by the nature of the stimulus to identify: insomniacs recognized both new and old sleep-related stimuli at lower spatial frequencies compared with good sleepers. The tendency to selectively attend to sleep-related stimuli may influence top-down processes occurring during identification of filtering stimuli, by determining a pre-allocation of attentional resources and facilitating identification processes even when sensorial information is scant. Differences in the identification processes of sleep-related stimuli compared with neutral ones should be carefully taken into account as possible pre-clinical markers of insomnia in poor sleepers.

SIM: A Search Engine by Correlating Scattered Data Sets for Cyber, Physical, and Social Systems

How to effectively locate a file in the emerging cyber, physical, and social systems is becoming a very important challenge due to the convergence of everyday life devices. A typical scenario goes like this. If you do not remember anything about a file (such as keywords or some text in the document) except some fragmented memories of what you are looking for, how can you locate the target in one of the many large folders in the system? A potential solution would be to use whatever you remember as a stepping stone along a path that leads to a small set of candidate targets. This paper proposes the design of a desktop search engine, Search Implicit Memories (SIM), which leverages both explicit and implicit memories. Explicit memories are employed as stepping stones to tap into the implicit memories, and locate the target in the implicit memories. The paper also proposes to monitor and correlate the existing data sets distributed across computer users' disk file systems to track user activities and construct correlation graphs. Experimental results show that SIM is both effective and lightweight. SIM can be used to complement existing keyword-based desktop search engines.

Delta and theta activity during slow-wave sleep are associated with declarative but not with non-declarative learning in children with sleep-disordered breathing

Sleep-disordered breathing (SDB) is a prevalent sleep disorder among young children and is associated with daytime impairments, such as behavioral dysregulation, affective symptoms, and reduced cognitive performance. Microstructural changes of non-rapid eye movement sleep, particularly the reduction of slow frequency oscillations during slow-wave sleep (SWS) might be associated with impaired learning among children with SDB. In this study, we investigated the associations between learning capacity, overnight memory retention, and post-learning, spectral power density of SWS within a clinical sample of children (n = 27) with SDB. Participants performed a declarative (the “War of the Ghosts”) and a non-declarative (the “Alternating Serial Reaction Time”) memory task at night, before their clinical (nighttime polysomnographic) evaluation. Memory retention was assessed in the morning. Overnight changes in performance in the declarative and non-declarative task were not related to relative spectral power measu...

A photograph of a little boy seen through the lens of the associative unconscious and collective memory

This article focuses on a photograph of a little boy that was taken in 1944. Photographs, when viewed many years later, often bring back deep experiences, long past and somehow forgotten. Revisiting this photo 70 years later, the author began to experience it as an “evocative object” – that is, one with not merely a personal meaning, but a “social and cultural significance” as well (Bollas, 2009a, p.179). Associations to the photo brought back countless memories, which opened up wider social-historical dimensions. Using the concepts of collective memory and the associative unconscious, the author explores this single photograph to evoke the immense possibilities for new thinking that emerge from this medium.

What psychological process is reflected in the FN400 event-related potential component?

During many recognition contexts, old items elicit a more positive event-related potentials (ERPs) than new items at mid-frontal electrodes about 300–500ms. The psychological processes that are reflected in is ERP component (i.e., the FN400) has been vigorously debated. Some argue that the FN400 reflects familiarity, whereas others argue that it reflects conceptual implicit memory. Three experiments contrasted these two hypotheses by presenting pre-experimentally familiar (i.e., name-brand) products and novel, off-brand products. In addition, some of the off-brand products were conceptually primed by the name-brand product to determine how FN400 amplitude would be affected by conceptually primed, but novel, products. The results provided mixed support for both theoretical views, and it is integrated with a broader theoretical framework to characterize the psychological processes captured by the FN400.

The Development of Implicit Memory From Infancy to Childhood: On Average Performance Levels and Interindividual Differences.

The present multimethod longitudinal study aimed at investigating development and stability of implicit memory during infancy and early childhood. A total of 134 children were followed longitudinally from 3months to 3years of life assessing different age-appropriate measures of implicit memory. Results from structural equationmodeling give further evidence that implicit memory is stable from 9months of life on, with earlier performance predicting later performance. Second, it was found that implicit memory is present from early on, and no age-related improvements are found from 3months on. Results are discussed with respect to the basic brain structures implicit memory builds on, as well as methodological issues.

Attempts to Suppress Episodic Memories Fail but do Produce Demand: Evidence from the P300-Based Complex Trial Protocol and an Implicit Memory Test.

Instructions to voluntarily suppress memories of a mock crime have been reported to result in decreased P300 amplitude during a P300-based concealed information test (CIT) and reduced autobiographical Implicit Association Test (aIAT) D scores, supporting successful suppression. However, one such study, (Hu et al., Psychological science 26(7):1098-1106, 2015) used the P300-based Complex Trial Protocol with a 50-50 target to nontarget ratio, which could impose much response switching and thereby drain cognitive resources, also resulting in reduced P300. The present study replicated Hu et al. (Psychological science 26(7):1098-1106, 2015) with one major variation-a less intrusive 20-80 target to nontarget ratio that required less response switching. Detection rates were high using both the brainwave-based CIT (90% accuracy) and the aIAT (87% accuracy). However we found no significant differences between the suppression and simple guilty groups on the major indices of concealed information detection, which compare probe and irrelevant P300 responses. While we did find that overall P300 amplitude was reduced in the suppression group, this reduction was not specific to probe responses. Additionally, while there were group differences in aIAT hit rates, there were no differences in aIAT D scores. Taken together, these findings suggest that the previously demonstrated reductions in P300 are a reflection of task demand rather than of effective voluntary memory suppression.

Dyslexics' faster decay of implicit memory for sounds and words is manifested in their shorter neural adaptation.

Dyslexia is a prevalent reading disability whose underlying mechanisms are still disputed. We studied the neural mechanisms underlying dyslexia using a simple frequency-discrimination task. Though participants were asked to compare the two tones in each trial, implicit memory of previous trials affected their responses. We hypothesized that implicit memory decays faster among dyslexics. We tested this by increasing the temporal intervals between consecutive trials, and by measuring the behavioral impact and ERP responses from the auditory cortex. Dyslexics showed a faster decay of implicit memory effects on both measures, with similar time constants. Finally, faster decay of implicit memory also characterized the impact of sound regularities in benefitting dyslexics' oral reading rate. Their benefit decreased faster as a function of the time interval from the previous reading of the same non-word. We propose that dyslexics' shorter neural adaptation paradoxically accounts for their longer reading times, since it reduces their temporal window of integration of past stimuli, resulting in noisier and less reliable predictions for both simple and complex stimuli. Less reliable predictions limit their acquisition of reading expertise.

Resource Availability and Explicit Memory Largely Determine Evaluative Conditioning Effects in a Paradigm Claimed to be Conducive to Implicit Attitude Acquisition

In three experiments, we investigated how preventing the explicit encoding of conditioned stimulus–unconditioned stimulus (CS–US) pairings by imposing a secondary task at learning influences evaluative conditioning (EC) effects in a paradigm claimed to be conducive to implicit EC. We additionally used a multinomial processing tree model to examine how the resource depletion manipulation affects explicit and implicit memory contributions to EC. In all experiments, the EC effect largely vanished when a secondary task was employed that severely reduced participants’ explicit memory for the CS–US pairings. Furthermore, no evidence obtained for an implicit memory contribution to EC effects. In conclusion, the present research yields evidence for explicit learning, but no support for the contribution of implicit processes to EC in a paradigm claimed to facilitate implicit EC.

Use of hypnosis, meditation, and biofeedback in dermatology

Hypnosis utilizes trance to access otherwise inaccessible repressed or unconscious memories and features of the psyche and control of physiology not attainable in the ordinary conscious waking state. Medical uses of hypnosis in dermatology include reducing discomfort from itching or skin pain, altering ingrained dysfunctional habits such as scratching, promoting healing of skin disorders, searching for psychosomatic aspects of skin disorders and alleviating them, and reframing cognitive and emotional dysfunctional patterns related to skin disorders. Meditation uses trance to center and balance. Medical uses of meditation in dermatology include relaxation to promote healing of skin disorders and refocusing with respect to the meaning and emotional negative valance of skin disorders. Biofeedback in dermatology employs instrumentation with visual or auditory feedback to permit conscious awareness and alteration of physiologic phenomena such as sweating as measured by galvanic skin resistance and skin temperature measured by temperature detecting devices, promoting relaxation and healing. These methods and techniques permit access to and intervention in otherwise inaccessible areas that can influence skin disorders. With proper use, they are very safe, with minimal, if any, side effects and sometimes produce significant results where other methods have failed.

When Bigger Is Better (and When It Is Not): Implicit Bias in Numeric Judgments

Numeric ratings for products can be presented using a bigger-is-better format ( 1=bad, 5=good ) or a smaller-is-better format with reversed rating poles ( 1=good, 5=bad ). Seven experiments document how implicit memory for the bigger-is-better format—where larger numbers typically connote something is better—can systematically bias consumers’ judgments without their awareness. This rating polarity effect is the result of proactive interference from culturally determined numerical associations in implicit memory and results in consumer judgments that are less sensitive to differences in numeric ratings. This is an implicit bias that manifests even when people are mindful and focused on the task and across a range of judgment types (auction bids, visual perception, purchase intent, willingness-to-pay). Implicating the role of reliance on implicit memory in this interference effect, the rating polarity effect is moderated by (i) cultural norms that define the implicit numerical association, (ii) construal mindsets that encourage reliance on implicit memory, and (iii) individual propensity to rely on implicit memory. This research identifies a new form of proactive interference for numerical associations, demonstrates how reliance on implicit memory can interfere with explicit memory, and shows how to attenuate such interference.

A nonmusician with severe Alzheimer’s dementia learns a new song

ABSTRACTThe hallmark symptom of Alzheimer’s Dementia (AD) is impaired memory, but memory for familiar music can be preserved. We explored whether a non-musician with severe AD could learn a new song. A 91 year old woman (NC) with severe AD was taught an unfamiliar song. We assessed her delayed song recall (24 hours and 2 weeks), music cognition, two word recall (presented within a familiar song lyric, a famous proverb, or as a word stem completion task), and lyrics and proverb completion. NC’s music cognition (pitch and rhythm perception, recognition of familiar music, completion of lyrics) was relatively preserved. She recalled 0/2 words presented in song lyrics or proverbs, but 2/2 word stems, suggesting intact implicit memory function. She could sing along to the newly learnt song on immediate and delayed recall (24 hours and 2 weeks later), and with intermittent prompting could sing it alone. This is the first detailed study of preserved ability to learn a new song in a non-musician with severe AD, and contributes to observations of relatively preserved musical abilities in people with dementia.