Feeling of knowing in episodic memory following moderate to severe closed-head injury

Validation of a rodent model of episodic memory replay

Vivid episodic memories in humans have been described as the replay of the flow of past events in sequential order. Recently, Panoz-Brown et al. Current Biology, 28, 1628-1634, (2018) developed an olfactory memory task in which rats were presented with a list of trial-unique odors in an encoding context; next, in a distinctive memory assessment context, the rats were rewarded for choosing the second to last item from the list while avoiding other items from the list. In a different memory assessment context, the fourth to last item was rewarded. According to the episodic memory replay hypothesis, the rat remembers the list items and searches these items to find the item at the targeted locations in the list. However, events presented sequentially differ in memory trace strength, allowing a rat to use the relative familiarity of the memory traces, instead of episodic memory replay, to solve the task. Here, we directly manipulated memory trace strength by manipulating the odor intensity of target odors in both the list presentation and memory assessment. The rats relied on episodic memory replay to solve the memory assessment in conditions in which reliance on memory trace strength is ruled out. We conclude that rats are able to replay episodic memories.

Lack of effects of online HD-tDCS over the left or right DLPFC in an associative memory and metamemory monitoring task

Neuroimaging studies have shown that activity in the prefrontal cortex correlates with two critical aspects of normal memory functioning: retrieval of episodic memories and subjective "feelings-of-knowing" about our memory. Brain stimulation can be used to test the causal role of the prefrontal cortex in these processes, and whether the role differs for the left versus right prefrontal cortex. We compared the effects of online High-Definition transcranial Direct Current Stimulation (HD-tDCS) over the left or right dorsolateral prefrontal cortex (DLPFC) compared to sham during a proverb-name associative memory and feeling-of-knowing task. There were no significant effects of HD-tDCS on either associative recognition or feeling-of-knowing performance, with Bayesian analyses showing moderate support for the null hypotheses. Despite past work showing effects of HD-tDCS on other memory and feeling-of-knowing tasks, and neuroimaging showing effects with similar tasks, these findings add to the literature of non-significant effects with tDCS. This work highlights the need to better understand factors that determine the effectiveness of tDCS, especially if tDCS is to have a successful future as a clinical intervention.

Temporal foundations of episodic memory

A fundamental question in the development of animal models of episodic memory concerns the role of temporal processes in episodic memory. Gallistel, (1990) developed a framework in which animals remember specific features about an event, including the time of occurrence of the event and its location in space. Gallistel proposed that timing is based on a series of biological oscillators, spanning a wide range of periods. Accordingly, a snapshot of the phases of multiple oscillators provides a representation of the time of occurrence of the event. I review research on basic timing mechanisms that may support memory for times of occurrence. These studies suggest that animals use biological oscillators to represent time. Next, I describe recently developed animal models of episodic memory that highlight the importance of temporal representations in memory. One line of research suggests that an oscillator representation of time supports episodic memory. A second line of research highlights the flow of events in time in episodic memory. Investigations that integrate time and memory may advance the development of animal models of episodic memory.

The Power of Perception: Beliefs About Memory Ability Uniquely Contribute to Memory Performance and Quality of Life in Adults Aging with Traumatic Brain Injury

OBJECTIVE

Personal beliefs about memory ability, which comprise memory self-efficacy (MSE), can influence memory performance in healthy older adults. Self-efficacy theory also predicts that MSE biases self-perceptions of functioning more globally, potentially impacting daily activity beyond cognitive performance. People with traumatic brain injury (PwTBI) frequently report debilitating memory problems long after acute recovery, but little is known about how MSE affects health outcomes in this population. We examined demographic and clinical correlates of MSE, as well as its relationship to memory test performance and health-related quality of life (QOL), in older adults with chronic moderate-to-severe TBI (msTBI).

METHOD

One hundred fourteen adults, aged 50+ and at least 1 year post-msTBI, underwent neuropsychological testing to assess their memory functioning. Participants also self-reported levels of psychological distress, MSE (Cognitive Confidence subscale of the Metacognitions Questionnaire), and health-related QOL (Quality of Life after Brain Injury questionnaire).

RESULTS

Demographic and injury-related predictors showed weak correlations with MSE. Although the relationship between MSE and general psychological distress was robust, only the former significantly predicted memory performance. Bivariate analyses revealed significant relationships between MSE and five out of the six QOL domains assessed. Multivariate linear regression revealed a significant impact of MSE on overall QOL independent of demographic and clinical variables.

CONCLUSIONS

Our findings support a unique role for MSE in both the objective cognitive performance and subjective health of PwTBI. Increased focus on self-perceptions of ability and their impact on measured outcomes is an important step towards personalized rehabilitation for adults with chronic msTBI.

Level of processing's effect on episodic retrieval following traumatic brain injury in the elderly: An event-related potential study

Individuals who have sustained a traumatic brain injury (TBI) can suffer from episodic memory impairments. Until now, the neural correlates underlying episodic retrieval in individuals with TBI remained scarce, particularly in older adults. We aimed to fill this gap by recording event-related potentials during an old/new episodic recognition task in 26 older adults, 13 healthy and 13 with TBI. The task manipulated the level of processing in encoding with the use of semantic organizational strategies (deep guided, deep self-guided, and shallow encoding). For all encoding conditions, behavioral data analyses on the discrimination rate indicated that older adults with TBI were globally impaired compared with healthy older adults. The electrophysiological results indicated that the left-parietal effect was larger in the deep guided condition than in the shallow condition. In addition, the results show that the mid-frontal and left-parietal positive old/new effects were absent in both groups. The main findings are the observation, in the control group only, of an early frontal old/new effect (P200; 150-300 ms) and of a late frontal old/new effect on the left hemisphere, only in the Spontaneous condition. Together, results suggest an impairment of the allocation of attentional resources and working memory necessary for retrieving and monitoring items in the elderly with TBI.

Postdecisional Processing Delays in Metacognitive Monitoring After Traumatic Brain Injury

OBJECTIVE

To document the process by which metacognitive judgments ("online" monitoring of one's own cognitive performance during task completion) are made after traumatic brain injury (TBI).

PARTICIPANTS

Sixteen community-dwelling adults with moderate to severe TBI and 16 matched healthy controls.

DESIGN

Prospective, cross-sectional design.

MEASURES

Metacognitive retrospective confidence judgments and reaction times were collected as participants performed a metamemory task.

RESULTS

Adults with TBI did not differ from healthy peers in metacognitive accuracy; however, they took significantly longer to make retrospective confidence judgments. Retrospective confidence judgment reaction times were not consistently correlated to measures of processing speed in either sample.

CONCLUSIONS

Adults with TBI engage in different postdecisional processes to make metacognitive judgments compared with healthy controls. Findings suggest that reaction times may be an important dimension of metacognition to assess clinically after TBI.

Predicting Remembering: Judgments of Prospective Memory After Traumatic Brain Injury

PURPOSE

Adults with traumatic brain injuries (TBIs) often struggle with prospective memory (PM), the ability to remember to complete tasks in the future, such as taking medicines on a schedule. Metamemory judgments (or how well we think we will do at remembering) are linked to strategy use and are critical for managing demands of daily living. The current project used an Internet-based virtual reality tool to assess metamemory judgments of PM following TBI.

METHOD

Eighteen adults with moderate to severe TBI and 20 healthy controls (HCs) played Tying the String, a virtual reality game with PM items embedded across the course of a virtual work week. Participants studied PM items and made two judgments of learning about the likelihood of recognizing the CUE, that is, when the task should be done, and of recalling the TASK, that is, what needed to be done.

RESULTS

Participants with TBI adjusted their metamemory expectations downward, but not enough to account for poorer recall performance. Absolute difference scores of metamemory accuracy showed that healthy adults were underconfident across PM components, whereas adults with TBI were markedly overconfident about their ability to recall TASKs.

CONCLUSIONS

Adults with TBI appear to have a general knowledge that PM tasks will be difficult but are poor monitors of actual levels of success. Because metamemory monitoring is linked to strategy use, future work should examine using this link to direct PM intervention approaches.

Evaluating semantic metamemory: Retrospective confidence judgements on the information subtest

The current research explored the potential value of adding a supplementary measure of metamemory to the Information subtest of the Wechsler Adult Intelligence Scale - Third Edition (WAIS-III in Study 1) or Fourth Edition (WAIS-IV in Study 2) in order to assess its relationship to other neuropsychological measures and to brain injury. After completing the Information subtest, neuropsychological examinees were asked to make retrospective confidence judgements (RCJ) by rating their answer certainty in the original order of item administration. In Study 1 (N = 52) and study 2 (N = 30), correct answers were rated with significantly more certainty than wrong answers (termed a "confidence gap"), and in both studies, higher confidence for wrong answers was significantly correlated with poorer performance on the Wisconsin Card Sorting Test (for categories completed r = -.58 in Study 1, and r = -.47 in Study 2; for perseverative errors r = .44 in Study 1, and r = .45 in Study 2). In both studies, a number of examinees with positive CT findings had a very small or reversed confidence gap. These findings suggest that semantic metamemory is sensitive to executive functioning and brain injury and should be assessed in the neuropsychological examination.

Implicit memory influences on metamemory during verbal learning after traumatic brain injury

PURPOSE

Prior research has shown that individuals with traumatic brain injury (TBI) may be overconfident in their judgments of learning (JOLs; online measures of self-monitoring of learning and memory). JOLs had been presumed to be driven by explicit processes, but recent research has also revealed implicit memory involvement. Given that implicit learning mechanisms are often intact in those with TBI, the purpose of this study was to investigate whether priming and antipriming of immediate and delayed JOLs in individuals with TBI might affect their overconfidence.

METHOD

A standard 3-field masked priming paradigm was combined with a paired-associate learning task with JOLs and administered to individuals with TBI and matched controls (18 per group). In each trial, a subliminal masked stimulus was immediately followed by supraliminal presentation of a word pair for study; participants also made immediate and delayed JOLs, with cued-recall testing 10 min after study and judgment.

RESULTS

Antipriming significantly lowered JOLs and overconfidence for both groups, whereas delaying JOLs significantly improved recall for both groups.

CONCLUSIONS

The results suggest that JOLs may be influenced by subliminal implicit memory. Clinical implications include the possible use of antipriming to reduce overconfidence after brain injury and delaying JOLs to improve recall.

A systematic review of the assessment tools used to measure metamemory in patients with brain injury

[Purpose] The purpose of this study was to provide various assessment tools for metamemory of a patient with brain injury to develop accurate metamemory measurement methods which can be effectively applied in rehabilitation training programs in clinics. [Subjects and Methods] For this study, we carried out a systematic document search of the literature for articles published between January, 2001, and December, 2013, in order to review studies of measurement tools used to assess the metamemory of patients with brain injury. [Results] The initial search of the databases yielded 57 articles, 48 of which did not meet the inclusion criteria. Thus 9 studies were included in our review. The quality level of all the studies was IIA2b and PEDro scale scores were found to range from 4 to 6. [Conclusion] More studies need to be made, using various measurement tools for metamemory of more diverse patient groups. We believe studies should be made of the assessment of metamemory and interventions for it in accordance with the diagnoses and the cognitive levels of the patients with brain injury.

Tarefa experimental de metamemória para avaliar monitoramento e controle de memória

Tarefas experimentais para avaliar processos de monitoramento e controle de memória permitem o exame online dessas habilidades. No âmbito nacional, estas tarefas ainda precisam ser desenvolvidas, facilitando e incentivando projetos de pesquisa futuros. Este artigo apresenta os passos para a construção de uma tarefa para avaliação dos processos de monitoramento e controle. No Estudo 1, é descrita a seleção de 100 estímulos (pares de palavra pista-alvo) e suas características psicolinguísticas. O Estudo 2 apresenta dados do estudo piloto da tarefa com dez adultos, com foco na avaliação do monitoramento. No Estudo 3, são apresentados dados de processos de monitoramento e controle num estudo piloto com 12 universitários, um caso clínico pós-AVC e dois idosos neurologicamente saudáveis. Os resultados apontaram a necessidade de duas versões da tarefa, para diferentes populações, que permitisse a variabilidade dos dados intra e entre participantes. Também surgiram achados preliminares pertinentes a importantes hipóteses da área da metamemória.

Does This Ring a Bell? Music-cued Retrieval of Semantic Knowledge and Metamemory Judgments

Failed knowledge recall attempts are sometimes accompanied by a strong feeling of imminent success, giving rise to a “tip-of-the-tongue” (TOT) experience. Similar to successful retrieval (i.e., the Know state, K), a TOT commences with strong cue familiarity but involves only partial retrieval of related information. We sought to characterize the cognitive processes and temporal dynamics of these retrieval states and to extend the applicability of previous findings about TOT to the auditory modality. Participants heard 3-sec initial segments of popular songs and were asked to recall their names. EEG was recorded while participants indicated their retrieval state via button press. Stimulus-locked analyses revealed a significant early left fronto-central difference between TOT and K, at 300–550 msec postcue onset. Post hoc analysis revealed that, in this time window, TOT also differed from DK (Don't Know) responses, which themselves were similar to the K responses. This finding indicates that neural processes, which may reflect strategy selection, ease of semantic processing, familiarity-related processes, or conflict monitoring, are indicative of the fate of our knowledge judgments long before we actually execute them.

Are all judgments created equal? An fMRI study of semantic and episodic metamemory predictions

Metamemory refers to the ability of individuals to monitor and control their own memory performance. Although little theoretical consideration of the possible differences between the monitoring of episodic and of semantic knowledge has been published, results from patient and drug studies that used the "feeling of knowing" (FOK) paradigm show a selective impairment in the accuracy of episodic monitoring but not in its semantic counterpart. Similarly, neuroimaging studies provide indirect evidence for separate patterns of activation during episodic or semantic FOKs. However, the semantic-episodic distinction hypothesis has not been directly addressed. In the current event-related fMRI study, we used a within-subject, within-experiment comparison of the monitoring of semantic and episodic content. Whereas the common neural correlates of episodic and semantic FOKs observed in this study generally replicate the previous neuroimaging findings, several regions were found to be differentially associated with each task. Activity of the right inferior frontal gyrus was modulated by the semantic-episodic factor only during the negative predictions of retrieval, suggesting that negative predictions are based on partially distinct mechanisms during each task. A posterior midline network, known to be activated during episodic retrieval, was activated during episodic and not semantic monitoring, suggesting that episodic FOKs rely, to some extent, on common episodic retrieval processes. These findings suggest that theoretical accounts of the etiology and function of FOKs may benefit from incorporating the prediction directionality (positive/negative) and the memory domain (semantic/episodic) distinctions.

Predictions of episodic memory following moderate to severe traumatic brain injury during inpatient rehabilitation

We examined memory self-awareness and memory self-monitoring abilities during inpatient rehabilitation in participants with moderate to severe traumatic brain injury (TBI). A total of 29 participants with moderate to severe TBI and 29 controls matched on age, gender, and education completed a performance prediction paradigm. To assess memory self-awareness, participants predicted the amount of information they would remember before completing list-learning tasks and visual-spatial memory tasks. Memory self-monitoring was assessed by participants' ability to increase accuracy of their predictions after experience with the tests. Although the TBI participants performed more poorly than controls on both episodic memory tasks, no significant group differences emerged in memory self-awareness or memory self-monitoring. The TBI participants predicted that their memory performances would be poorer than that of controls, accurately adjusted their predictions in accordance with the demands of the tasks, and successfully modified their predictions following experience with the tasks. The results indicate that moderate to severe TBI individuals in the early stages of recovery can competently assess the demands of externally driven metamemorial situations and utilize experience with task to accurately update their knowledge of memory abilities.