Item Memory Research Articles

Abstract WP186: Fewer Self-reported Memory Problems Are Associated With Better Blood Pressure Control Post-stroke

Introduction: Memory problems, a common cognitive issue, can have a negative influence on one’s ability to function and contributes to increased risk of secondary stroke. Objective: To examine the association between self-reported memory problems at 6 months and blood pressure control at 12 months post-stroke. Methods: This study utilized follow-up data from the Discharge Educational Strategies for Reduction of Vascular Events (DESERVE) stroke risk factor reduction trial (n=226). Sample size was restricted to those who answered memory questions and had a 12-month blood pressure (BP) reading. Exclusion criteria for DESERVE included any significant memory disorder prior to the baseline stroke. Seven memory domain questions (Table 1) from the Stroke Impact Scale were used separately to assess the association with systolic BP, with control defined as ≤120mmHg, at 12 months in logistic regression models adjusted for race, gender, education, age, and intervention status. Models were additionally adjusted for 6-month BP control as a mediator. Results: Participants were almost equally white (28%), Black (33%), or Hispanic (34%) and 52% were female with a mean age of 65 (SD=13). About 25% had BP control at 6 or 12 months. Memory measures were not significantly associated with BP control prior to adjusting for BP control at 6 months. After adjusting for 6-month BP control, participants with less difficulty remembering things that people just told them (OR=1.69, 95% CI: 1.09, 2.63) or remembering to do things (OR=1.76, 95% CI:1.09, 2.86) had better odds of having their BP controlled at 12 months. Memory items 2 and 4-7 did not show an association with better BP control. Discussion: Stroke survivors who were better at remembering what people told them and remembering to do things were more likely to achieve blood pressure control 1-year post-stroke. Evaluating early memory post-stroke may be an important target for secondary prevention strategies and should be further researched.

Impaired cognitive performance in older adults is associated with deficits in item memory and memory for object features

Amnestic mild cognitive impairment (aMCI) is associated with damage to the perirhinal/entorhinal cortex, and consequently, deficits in item/object memory. However, cognitive assessments commonly used to identify individuals with aMCI require a clinician to administer and interpret the test. We developed a novel self-administered global cognitive assessment, called the Cognitive Assessment via Keyboard (CAKe). To assess the relationship between CAKe performance and perirhinal/entorhinal cortex-dependent memory function, participants completed the CAKe, a feature source memory task, and a context memory task. During the memory tasks, participants studied line drawings with either a green or orange internal color (feature memory runs) or external color (context memory runs) and then classified each item as old and previously presented with a “green” or “orange” color, or “new”. CAKe scores were correlated with item memory accuracies and source memory accuracies on both tasks. Participants with ‘impaired’ CAKe performance had worse item memory and worse feature source memory accuracies than those with ‘normal’ CAKe performance. These results demonstrate specific deficits in item memory and feature source memory and suggest that our assessments may be a valid predictor of aMCI memory deficits.

Individual differences in autobiographical memory: a Danish version of the Autobiographical Recollection Test (ART)

Individual differences in autobiographical memory have become an area of growing research interest. Recently, the Autobiographical Recollection Test (ART; Berntsen et al., 2019) was introduced. The ART measures individual differences in autobiographical memory along seven components: Vividness, narrative coherence, reliving, rehearsal, scene, visual imagery, and life story relevance. The ART is a useful and easily administered tool, but is so far not available in any of the Nordic languages. The aim of the present study was to provide a Danish translation of the ART and to provide correlations between the Danish ART and characteristics of randomly sampled memories (i.e. memories cued by words) in order to support the validity of the translation. First, the ART was translated into Danish. Then, 122 Danish adults filled out the Danish ART and rated the recollective qualities of three word cued autobiographical memories. The internal consistency was in line with findings on the original English version of the scale as were correlations between the Danish ART, Brief ART and the seven components of the ART. The Danish ART correlated positively with characteristics of the word cued memories corresponding to the seven components of the ART. Additional analyses demonstrated that the magnitude of these correlations were similar to those between ratings of individual memory items, supporting the validity of the ART as a trait-like measure of the recollective experience of autobiographical memory. The ART could be of interest to many areas of psychology and potential applications of the ART are discussed.

Memory for the News: Does Event Transience Matter?

Health providers frequently probe patients' recall of current and/or remote news events to determine the extent of memory loss. Impaired memory for transient events (ie, in the news for a circumscribed time) may provide information regarding the onset of cognitive impairment. To use the Transient News Events Test (TNET) to explore how memory changes over time in both older adults with cognitive impairment (CI) and noncognitively impaired (NCI) older adults. We also investigated the role of episodic and semantic memory on TNET performance. Sixty-seven older adults completed the TNET as part of a comprehensive neuropsychological assessment. Analyses included t tests to evaluate group differences for TNET score and correlations between TNET and neuropsychological measures, including episodic and semantic memory tests. NCI adults demonstrated better memory for TNET items than adults with CI. The NCI and CI groups did not differ regarding memory for remote events; however, the CI group exhibited worse memory for recent events. There was a significant association between TNET score and the capacity for episodic and semantic memory in the CI group. In the NCI group, TNET score was significantly associated with episodic memory. Findings support the use of transient news events to assess remote memories in older adults. Novel remote memory measures broaden the scope of memory assessment far beyond what is feasible with traditional neuropsychological assessment and may provide insight into the onset of memory changes.

Does unitization really function like items? The role of interference on item and associative memory processes.

Associative memory declines as we age, while item memory remains relatively stable. Previous work has shown that, in both younger and older adults, while item recognition declines linearly across time and interference, associative recognition declines only with longer delays and more interference. Unitization is a memory process found to support associative memory by allowing pairs to presumably be processed like single items. Research has found that unitization can benefit memory in aging by boosting associative memory to be on par with that of younger adults. Yet it remains unclear exactly the mechanism responsible for this enhancement in memory. The current studies aimed to determine whether unitized pairs show similar memory to that of items or associations with increasing time and interference, and determine how physically similar unitized pairs must be to perform like items and examine the effect of age on unitization in a continuous recognition paradigm. The results show that while unitized pairs exhibit higher corrected recognition compared with associative pairs at all lags, unitized pairs are not remembered to the degree that items are. It is critical that unitization boosts accurate recognition of pairs in both age groups across all early and middle lags compared with associative pairs. The results suggest that unitization may promote a more efficient associative link than unrelated associations over increasing time and interference, but the benefit does not reach that of item memory. These results demonstrate that while unitization benefits corrected recognition with earlier interference, its effect may not hold with later interference.

The Categorical Deviation Effect May Be Underpinned by Attentional Capture: Preliminary Evidence from the Incidental Recognition of Distracters

ABSTRACT The performance of a visual focal task is appreciably disrupted by an unexpected change (or deviation) in the properties of a task irrelevant auditory background. A vast amount of evidence suggests that a change in the acoustic properties of sound disrupts performance via attentional capture. However, an emerging body of evidence suggests that the disruption of task performance by a change in semantic category within a stream of sounds does not behave the same and is therefore not produced by attentional capture. This preliminary study aimed to further investigate whether the disruption produced by a categorical deviant was underpinned by attentional capture. In a single experiment, participants were presented with an irrelevant sound stream while they memorized a categorized list for free recall. We examined whether free recall performance was disrupted by an unexpected change in category within the sound and later investigated, via a surprise recognition test, whether participants had superior memory for deviant items as compared to items from the same positions in control sequences. Results revealed that the categorical deviation effect manifested in poorer free recall performance. Additionally, post-study, participants demonstrated better recognition memory for deviant items compared to control items. On the assumption that explicit recognition requires attentional encoding of deviant items, our results yield evidence that the categorical deviation effect may indeed be produced via attentional capture.

Memory-augmented appearance-motion network for video anomaly detection

Video anomaly detection is a promising yet challenging task, where only normal events are observed in the training phase. Without any explicit classification boundary between normal and abnormal events, anomaly detection can be turned into an outlier detection problem by regarding any event that does not conform to the normal patterns as an anomaly. Most of the existing works mainly focus on improving the representation of normal events, while ignore the relationship between normal and abnormal events. Besides, the lack of restrictions on classification boundaries also leads to performance degradation. To address the above problems, we design a novel autoencoder-based Memory-Augmented Appearance-Motion Network (MAAM-Net), which consists of a novel end-to-end network to learn appearance and motion feature of a given input frame, a fused memory module to build a bridge for normal and abnormal events, a well-designed margin-based latent loss to relieve the computation costs, and a pointed Patch-based Stride Convolutional Detection (PSCD) algorithm to eliminate the degradation phenomenon. Specifically, the memory module is embedded between the encoder and decoder, which serves as a sparse dictionary of normal patterns, therefore it can be further employed to reintegrate abnormal events during inference. To further distort the reintegration quality of abnormal events, the margin-based latent loss is leveraged to enforce the memory module to select a sparse set of critical memory items. Last but not least, the simple yet effective detection method focuses on patches rather than the overall frame responses, which can benefit from the distortion of abnormal events. Extensive experiments and ablation studies on three anomaly detection benchmarks, i.e., UCSD Ped2, CUHK Avenue, and ShanghaiTech, demonstrate the effectiveness and efficiency of our proposed MAAM-Net. Notably, we achieve superior AUC performances on UCSD Ped2 (0.977), CHUK Avenue (0.909), and ShanghaiTech (0.713). The code is publicly available at https://github.com/Owen-Tian/MAAM-Net.

Pathways between multiple sclerosis, sleep disorders, and cognitive function: Longitudinal findings from The Nurses’ Health Study

Background: The potential mediating and moderating effects of sleep disorders on cognitive outcomes in multiple sclerosis (MS) have been insufficiently studied. Objectives: To determine direct and indirect longitudinal associations between sleep disorders and perceived cognitive dysfunction in women with MS. Methods: The 2013 and 2017 waves of the Nurses’ Health Study (n = 63,866) were utilized. All diagnoses and symptoms including MS (n = 524) were self-reported. Subjective cognitive function was measured using a composite score of four memory items and three binary outcomes that assessed difficulty following instructions, conversations/plots, and street navigation. Moderating and mediating effects of diagnosed/suspected obstructive sleep apnea (OSA), sleepiness, and insomnia between MS and cognition were estimated using the four-way decomposition method. Results: Prevalence of diagnosed/suspected OSA, sleepiness, and insomnia in 2013 were higher for nurses with MS (NwMS). NwMS were more likely to report cognitive difficulties in 2017. Insomnia mediated 5.4%–15.1% of the total effect between MS and following instructions, conversations/plots, and memory impairment, while sleepiness mediated 8.6%–12.3% of the total effect for these outcomes. In interaction analyses, OSA significantly accounted for 34% of the total effect between MS and following instructions. Conclusion: Prevalent OSA, insomnia, and sleepiness could differentially moderate or mediate the effect of MS on cognition in women with MS.

On separating long- and short-term memories in hyperdimensional computing.

Operations on high-dimensional, fixed-width vectors can be used to distribute information from several vectors over a single vector of the same width. For example, a set of key-value pairs can be encoded into a single vector with multiplication and addition of the corresponding key and value vectors: the keys are bound to their values with component-wise multiplication, and the key-value pairs are combined into a single superposition vector with component-wise addition. The superposition vector is, thus, a memory which can then be queried for the value of any of the keys, but the result of the query is approximate. The exact vector is retrieved from a codebook (a.k.a. item memory), which contains vectors defined in the system. To perform these operations, the item memory vectors and the superposition vector must be the same width. Increasing the capacity of the memory requires increasing the width of the superposition and item memory vectors. In this article, we demonstrate that in a regime where many (e.g., 1,000 or more) key-value pairs are stored, an associative memory which maps key vectors to value vectors requires less memory and less computing to obtain the same reliability of storage as a superposition vector. These advantages are obtained because the number of storage locations in an associate memory can be increased without increasing the width of the vectors in the item memory. An associative memory would not replace a superposition vector as a medium of storage, but could augment it, because data recalled from an associative memory could be used in algorithms that use a superposition vector. This would be analogous to how human working memory (which stores about seven items) uses information recalled from long-term memory (which is much larger than the working memory). We demonstrate the advantages of an associative memory experimentally using the storage of large finite-state automata, which could model the storage and recall of state-dependent behavior by brains.

Do developmental dyslexia and congenital amusia share underlying impairments?

ABSTRACT Developmental dyslexia and congenital amusia have common characteristics. Yet, their possible association in some individuals has been addressed only scarcely. Recently, two converging studies reported a sizable comorbidity rate between these two neurodevelopmental disorders (Couvignou et al., Cognitive Neuropsychology 2019; Couvignou & Kolinsky, Neuropsychologia 2021). However, the reason for their association remains unclear. Here, we investigate the hypothesis of shared underlying impairments between dyslexia and amusia. Fifteen dyslexic children with amusia (DYS+A), 15 dyslexic children without amusia (DYS-A), and two groups of 25 typically developing children matched on either chronological age (CA) or reading level (RL) were assessed with a behavioral battery aiming to investigate phonological and pitch processing capacities at auditory memory, perceptual awareness, and attentional levels. Overall, our results suggest that poor auditory serial-order memory increases susceptibility to comorbidity between dyslexia and amusia and may play a role in the development of the comorbid phenotype. In contrast, the impairments observed in the DYS+A children for auditory item memory, perceptual awareness, and attention might be a consequence of their reduced reading experience combined with weaker musical skills. Comparing DYS+A and DYS-A children suggests that the latter are more resourceful and/or have more effective compensatory strategies, or that their phenotype results from a different developmental trajectory. We will discuss the relevance of these findings for delving into the etiology of these two developmental disorders and address their implications for future research and practice.

Cognitive impairment in patients with heart failure: molecular mechanism and therapy.

Heart failure (HF) is associated with multiple organ dysfunction and many comorbidities. Its incidence is high among the elderly and is a major health burden worldwide. Cognitive impairment (CI) is highly prevalent in older patients with HF, which is an abnormality in one or more of the items of cognition, attention, memory, language, psychomotor function, and visual spatial acuity. Studies have shown that the incidence of CI in HF patients is between 13 and 54%, and patients with both conditions have poor self-care ability and prognosis, as well as increased mortality rates. However, the mechanisms of CI development in HF patients are still unclear. In this review, we describe the epidemiology and risk factors as well as measures of improving CI in HF patients. We update the latest pathophysiological mechanisms related to the neurocognitive changes in HF patients, expounding on the mechanisms associated with the development of CI in HF patients.

State, trait, and accumulated features of the Alzheimer's Disease Assessment Scale Cognitive Subscale (ADAS-Cog) in mild Alzheimer's disease.

The Alzheimer's Disease Assessment Scale Cognitive Subscale (ADAS-Cog) is used to assess decline in memory, language, and praxis in Alzheimer's disease (AD). A latent state-trait model with autoregressive effects was used to determine how much of the ADAS-Cog item measurement was reliable, and of that, how much of the information was occasion specific (state) versus consistent (trait or accumulated from one visit to the next). Participants with mild AD (n = 341) were assessed four times over 24 months. Praxis items were generally unreliable as were some memory items. Language items were generally the most reliable, and this increased over time. Only two ADAS-Cog items showed reliability >0.70 at all four assessments, word recall (memory) and naming (language). Of the reliable information, language items exhibited greater consistency (63.4% to 88.2%) than occasion specificity, and of the consistent information, language items tended to reflect effects of AD progression that accumulated from one visit to the next (35.5% to 45.3%). In contrast, reliable information from praxis items tended to come from trait information. The reliable information in the memory items reflected more consistent than occasion-specific information, but they varied between items in the relative amounts of trait versus accumulated effects. Although the ADAS-Cog was designed to track cognitive decline, most items were unreliable, and each item captured different amounts of information related to occasion-specific, trait, and accumulated effects of AD over time. These latent properties complicate the interpretation of trends seen in ordinary statistical analyses of trials and other clinical studies with repeated ADAS-Cog item measures. Studies have described unfavorable psychometric properties of the Alzheimer's Disease Assessment Scale Cognitive Subscale (ADAS-Cog), bringing into question its ability to track changes in cognition uniformly over time. There remains a need to estimate how much of the ADAS-Cog measurement is reliable, of that how much is occasion specific versus consistent, and of the consistent information, how much represents enduring traits versus autoregressive effects (i.e., effects of Alzheimer's disease [AD] progression carried over from one assessment to the next).A latent state-trait model with autoregressive effects in mild AD found most items to be unreliable, and each item to capture different amounts of occasion-specific, trait, and autoregressive information. Language items, specifically, naming and the memory item word recall, were the most reliable.Psychometric idiosyncrasies of individual items complicate the interpretation of their summed score, biasing ordinary statistical analyses of repeated measures in mild AD. Future studies should consider item trajectories individually.

Working memory capacity: the role of parameters of spiking neural network model

Purpose of this work is to study a computational model of working memory formation based on spiking neural network with plastic connections and to study the capacity of working memory depending on the time scales of synaptic facilitation and depression and the background excitation of the network. Methods. The model imitates working memory formation within synaptic theory: memorized items are stored in form of short-term potentiated connections in selective population but not in form of persistent activity. Integrate-And-Fire neuron model in excitable mode are used as network elements. Connections between excitatory neurons demonstrates the effect of short-term plasticity. Results. It is shown that the working memory capacity increases as calcium recovery time parameter grow up or the capacity increases with neurotransmitter recovery time parameter becomes lower. Working memory capacity is found to decrease to zero with decrease of the background excitation as a result of lower values of both the mean and the variance of the external noise. Conclusion. Working memory capacity was studied as a function of time scales of synaptic facilitation and depression and background excitation of the network. Estimated working memory capacity is shown to be possibly larger than classical experimental estimations of four items. But capacity strongly depends on intrinsic parameters of neural networks

Supplemental Material for Not What U Expect: Effects of Prediction Errors on Item Memory

Supplemental Material for Not What U Expect: Effects of Prediction Errors on Item Memory

The tradeoff between item and order information in short-term memory does not depend on encoding time.

Participants can optimize encoding of an immediate verbal memory test for item or for order information, or they can try to be ready for either type of test. Dividing encoding between both kinds of information, however, comes at a cost. Recently, it has been shown that the cost is more severe for order information compared to item information (Guitard et al., 2022). Here, for the first time, we evaluated which factor can better account for this asymmetry by contrasting two hypotheses. According to a rate hypothesis, divided attention affects the rate of encoding more for order than for items. According to an alternative, asymptote hypothesis, divided attention does not affect the rates but diminishes the endpoint, or asymptotic level, of order encoding more than item encoding. In three experiments to distinguish these hypotheses, participants prepared for an item fragment completion test, an order reconstruction test, or both types of tests, in trials with different durations of presentation. Overall, our results were better accounted for by a model which assumes that dividing attention between preparation for item and order testing affects the asymptote of encoding more for order than for items, with no effects on the rates of order or item encoding compared to preparation for a single test. The findings not only replicate our prior results, but also demonstrate that the allocation of attention to item or order processing can be disentangled from the time on task. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Autoimmune uveitis in Behçet's disease and Vogt-Koyanagi-Harada disease differ in tissue immune infiltration and T cell clonality.

Non-infectious uveitis is often secondary to systemic autoimmune diseases, with Behçet's disease (BD) and Vogt-Koyanagi-Harada disease (VKHD) as the two most common causes. Uveitis in BD and VKHD can show similar clinical manifestations, but the underlying immunopathogenesis remains unclear. To understand immune landscapes in inflammatory eye tissues, we performed single-cell RNA paired with T cell receptor (TCR) sequencing of immune cell infiltrates in aqueous humour from six patients with BD (N = 3) and VKHD (N = 3) uveitis patients. Although T cells strongly infiltrated in both types of autoimmune uveitis, myeloid cells only significantly presented in BD uveitis but not in VKHD uveitis. Conversely, VKHD uveitisbut not BD uveitis showed an overwhelming dominance by CD4+ Tcells (> 80%) within the T cell population due to expansion of CD4+ T cell clusters with effector memory (Tem) phenotypes. Correspondingly, VKHD uveitis demonstrated a selective expansion of CD4+ T cell clones which were enriched in pro-inflammatory Granzyme H+ CD4+ Tem cluster and showed TCR and Th1 pathway activation. In contrast, BD uveitis showed a preferential expansion of CD8+ T cell clones in pro-inflammatory Granzyme H+ CD8+ Tem cluster, and pathway activation for cytoskeleton remodelling, cellular adhesion and cytotoxicity. Single-cell analyses of ocular tissues reveal distinct landscapes of immune cell infiltration and T-cell clonal expansions between VKHD and BD uveitis. Preferential involvements of pro-inflammatory CD4+ Th1 cells in VKHD and cytotoxic CD8+ T cells in BD suggest a difference in disease immunopathogenesis and can guide precision disease management.

Effect of retrieval reward on episodic recognition with different difficulty: ERP evidence.

Previous studies found that the reward effect is stronger in more difficult retrieval tasks of item memory. However, it remains unclear whether the effect of reward is influenced by the memory task difficulty level in the source memory. We investigated the effects and neural mechanisms of the processing depth during encoding and rewards at retrieval on the item and source memory using event-related potentials (ERPs). Participants were required to carry out the congruity-judgment (deep processing) and size-judgment (shallow processing) tasks during encoding, and they completed separate object and background tests (half presented with reward) immediately after encoding. The results revealed that congruity-judgment (compare to size-judgment) task had longer response time in encoding phase, and evoked significantly greater reward differences at Prs (the hit rate minus the false alarm rate) in item retrieval, and the reward (relative to no reward) significantly improved recognition accuracy in source retrieval. ERP results also showed that congruity-judgment (compare to size-judgment) task evoked the larger N170, P3a, LPP and a decreased P3b of the stimuli in encoding phase, and elicited the wider distribution of LPC and LPN reward effects (i.e., the average amplitudes under the reward condition were significantly more positive than under the non-reward condition) in item retrieval, and the reward effects at FN400, LPC, and LPN were found only in the congruity-judged items with optimal difficulty in source retrieval. The results suggest that reward at retrieval evoked a greater boost in the congruity-judged stimuli, whether in item or source retrieval, which maybe be related to their optimal retrieval difficulty (Pr is closer to medium 0.50). This meant that the reward is more effective in memory retrieval with optimal difficulty.

Strategic adaptation to dual-task in verbal working memory: Potential routes for theory integration.

How working memory supports dual-task performance is the focus of a long-standing debate. Most previous research on this topic has focused on participant performance data. In three experiments, we investigated whether changes in participant-reported strategies across single- and dual-task conditions might help resolve this debate by offering new insights that lead to fruitful integration of theories rather than perpetuating debate by attempting to identify which theory best fits the data. Results indicated that articulatory suppression was associated with reduced reports of the use of rehearsal and clustering strategies but to an increase of the reported use of a visual strategy. Elaboration and clustering strategies were reported less for memory under dual task compared with single task. Under both dual task and articulatory suppression, more participants reported attempting to remember fewer memory items than were presented (memory reduction strategy). For arithmetic verification, articulatory suppression and dual task resulted in a reduction in reports of a counting strategy and an increase in reports of a retrieval strategy for arithmetic knowledge. It is argued that experimenters should not assume that participants perform the same task in the same way under different experimental conditions and that carefulty investigation of how participants change their strategies in response to changes in experimental conditions has considerable potential for resolving theoretical challenges. It is argued further that this approach points toward the value of attempting to integrate rather than proliferate theories of working memory. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

10 Minutes Frontal 40 Hz tACS-Effects on Working Memory Tested by Luck-Vogel Task.

Working memory is a cognitive process that involves short-term active maintenance, flexible updating, and processing of goal- or task-relevant information. All frequency bands are involved in working memory. The activities of the theta and gamma frequency bands in the frontoparietal network are highly involved in working memory processes; theta oscillations play a role in the temporal organization of working memory items, and gamma oscillations influence the maintenance of information in working memory. Transcranial alternating current stimulation (tACS) results in frequency-specific modulation of endogenous oscillations and has shown promising results in cognitive neuroscience. The electrophysiological and behavioral changes induced by the modulation of endogenous gamma frequency in the prefrontal cortex using tACS have not been extensively studied in the context of working memory. Therefore, we aimed to investigate the effects of frontal gamma-tACS on working memory outcomes. We hypothesized that a 10-min gamma tACS administered over the frontal cortex would significantly improve working memory outcomes. Young healthy participants performed Luck-Vogel cognitive behavioral tasks with simultaneous pre- and post-intervention EEG recording (Sham versus 40 Hz tACS). Data from forty-one participants: sham (15 participants) and tACS (26 participants), were used for the statistical and behavioral analysis. The relative changes in behavioral outcomes and EEG due to the intervention were analyzed. The results show that tACS caused an increase in the power spectral density in the high beta and low gamma EEG bands and a decrease in left-right coherence. On the other hand, tACS had no significant effect on success rates and response times. Conclusion: 10 min of frontal 40 Hz tACS was not sufficient to produce detectable behavioral effects on working memory, whereas electrophysiological changes were evident. The limitations of the current stimulation protocol and future directions are discussed in detail in the following sections.

Fronto-parietal single-trial brain connectivity benefits successful memory recognition.

Successful recognition has been known to produce distinct patterns of neural activity. Many studies have used spectral power or event-related potentials of single recognition-specific regions as classification features. However, this does not accurately reflect the mechanisms behind recognition, in that recognition requires multiple brain regions to work together. Hence, classification accuracy of subsequent memory performance could be improved by using functional connectivity within memory-related brain networks instead of using local brain activity as classifiers. In this study, we examined electroencephalography (EEG) signals while performing a word recognition memory task. Recorded EEG signals were collected using a 32-channel cap. Connectivity measures related to the left hemispheric fronto-parietal connectivity (P3 and F3) were found to contribute to the accurate recognition of previously studied memory items. Classification of subsequent memory outcome using connectivity features revealed that the classifier with support vector machine achieved the highest classification accuracy of 86.79 ± 5.93% (mean ± standard deviation) by using theta (3-8 Hz) connectivity during successful recognition trials. The results strongly suggest that highly accurate classification of subsequent memory outcome can be achieved by using single-trial functional connectivity.