Brain representations of space and time in episodic memory: A systematic review and meta-analysis.

All experiences preserved within episodic memory contain information on the space and time of events. The hippocampus is the main brain region involved in processing spatial and temporal information for incorporation within episodic memory representations. However, the other brain regions involved in the encoding and retrieval of spatial and temporal information within episodic memory are unclear, because a systematic review of related studies is lacking and the findings are scattered. The present study was designed to integrate the results of functional magnetic resonance imaging and positron emission tomography studies by means of a systematic review and meta-analysis to provide converging evidence. In particular, we focused on identifying the brain regions involved in the retrieval of spatial and temporal information. We identified a spatial retrieval network consisting of the inferior temporal gyrus, parahippocampal gyrus, superior parietal lobule, angular gyrus, and precuneus. Temporal context retrieval was supported by the dorsolateral prefrontal cortex. Thus, the retrieval of spatial and temporal information is supported by different brain regions, highlighting their different natures within episodic memory.

Polysomnographic parameters associated with cognitive function in patients with major depression and insomnia.

OBJECTIVE: To examine whether objective sleep parameters are associated with cognitive function (CF) in patients with major depressive disorder (MDD) with chronic insomnia (CI) and whether the severity of these disorders is related to CF. METHOD: Thirty patients with MDD with CI attending a tertiary care institution underwent two consecutive nights of polysomnographic (PSG) recording and a battery of neuropsychological tests, which included episodic memory, sustained attention, working memory, and executive function. The severity of MDD and CI was assessed by clinical scales. We examined the relationship between PSG parameters and CF, as well as whether the severity of the disorders is related to CF. RESULTS: Linear regression analysis revealed that total sleep time (TST) was positively associated with higher learning and recall of episodic memory, as well as better attention. Slow-wave sleep (SWS) showed a positive association with better working memory. Furthermore, wake after sleep onset (WASO) was negatively associated with episodic memory and lower attention. No significant relationships were found between the severity of MDD or CI with CF. CONCLUSION: Both sleep duration and depth are positively associated with several aspects of CF in patients with MDD with CI. Conversely, a lack of sleep maintenance is negatively related to CF in these patients. These findings could help identify modifiable therapeutic targets to reduce CF impairment.

Effects of different types of leisure activities on working memory across the adult lifespan.

The aim of the present study was to contrast the potential influence of five independent types of leisure activities (physical, mental, social, cultural, and passive) on working memory in a lifespan sample and in specific stages of adulthood (young, middle-aged, and older adults). A sample of 1652 healthy adults between 21 and 80 years of age participated in the study. Leisure activities were assessed through a lifestyle questionnaire created for the study. Working memory was measured in the verbal and spatial domains using a computerized n-back task that allowed us to reliably measure discrimination and reaction times. Across adulthood, mental (computer use and hobbies) and social leisure activities predicted greater verbal and spatial working memory discrimination; mental (reading) and social activities predicted faster verbal working memory; and mental (computer use) and physical activities predicted faster spatial working memory. In young adults, mental (computer use) and social activities were associated with greater verbal and spatial working memory performance. In middle-aged adults, physical and mental activities (computer use) were associated with greater working memory performance. In older adults, physical, mental (hobbies), and social activities were associated with greater working memory performance. Leisure activities can enhance working memory discrimination and speed independent of individuals' age.

Nutrient effects on working memory across the adult lifespan.

OBJECTIVE: To identify the nutrients that influence the performance of working memory, which is greatly affected as age progresses. METHOD: A total of 1646 healthy adults between 21 and 80 years old participated in the study. The daily consumption of 64 nutrients was examined using a food frequency questionnaire that assessed food intake during the previous year. Working memory was measured in the verbal and spatial domains using a computerized task. We examined which nutrients influence working memory across the entire adult lifespan and whether the influence of any of these nutrients on working memory is moderated by individuals' ages. RESULTS: Working memory, across the entire adult lifespan, benefits from the intake of cholesterol, alcohol, gamma- and delta-tocopherol, vitamin B6, and palmitoleic, oleic, alpha linoleic and linoleic acids. Moderator analyses revealed that fats, energy, lactose and sodium negatively influenced working memory in middle-aged and older adults, whereas vitamin D and vitamin C had positive effects on memory beyond 70 years of age. CONCLUSION: Nutrients have the ability to positively or negatively affect working memory, which varies as a function of age.

Effects of hypotension and hypertension on source memory and working memory.

OBJECTIVES: The effects of chronic low and high blood pressure on memory are unclear due to divergent results, originating in part due to participant misclassifications. The aim of this study was to compare source memory and working memory performance in individuals diagnosed with hypotension or hypertension with the performance of normotensive participants. Hypertensive and hypotensive individuals were receiving medical treatment. METHOD: From a sample of 1656 participants, 219 were identified as hypertensive, and 37 were identified as hypotensive. Each of these two groups was compared with normotensive individuals matched by age, education and sex. Source memory performance and working memory performance were assessed through computerized tasks. RESULTS: Source memory accuracy was poorer in hypotensive and hypertensive individuals than in normotensive individuals, and spatial working memory discrimination was inferior in hypertensive participants compared to normotensive individuals. CONCLUSION: Blood pressure impairment should be considered a major concern because it has been linked to severe cardiovascular and cerebrovascular diseases. Furthermore, here we show that it has negative effects on the two types of memory that are most essential for preserving a self-sufficient lifestyle.

Metamemory Mediates the Effects of Age on Episodic and Working Memory across the Adult Lifespan.

BACKGROUND: Previous studies have examined the direct relationship between metamemory and memory performance in young and older adults, but the results of these studies have been inconsistent. Therefore, we examined whether metamemory mediates the effects of age on memory performance. METHODS: We examined episodic memory and working memory through computerized tasks performed by a lifespan sample of 1554 healthy adults. Seven metamemory traits were measured with the Metamemory in Adulthood (MIA) questionnaire. Separate structural equation modeling analyses were conducted to investigate potential metamemory mediators that intervened between age and the accuracy and speed of accessing information from episodic and working memory. RESULTS: The use of internal or external strategies mediated the effects of age on episodic memory and spatial working memory performance. The perception of one's own memory capacity and the experience of anxiety when using memory functions mediated the effects of age on working memory performance in both domains. CONCLUSIONS: Metamemory traits have the power to strengthen or weaken the course of episodic and working memory decline throughout adulthood.

The Effects of Neurofeedback on Aging-Associated Cognitive Decline: A Systematic Review.

For more than a decade, neurofeedback interventions have been applied with the goal of improving cognitive functions in older adults. Some of these studies have been reviewed, but only in combination with experiments conducted in young adults or with studies seeking to modify functions not related to cognition. The purpose of the present review is to assess whether neurofeedback interventions benefit cognition in elderly adults. We included all neurofeedback studies conducted in older adults, whether healthy or affected by a clinical condition, that attempted to ameliorate any domain of cognition, with no restrictions by publication date. Fourteen studies were eligible for this review. Neurofeedback improved memory in healthy and unhealthy participants mainly when the theta and sensorimotor rhythm (SMR) frequencies were trained. In addition, other cognitive domains benefited from this intervention. Conversely, neurofeedback had no effect on attention processes. Although different studies used markedly different methods, almost all of them reported positive effects of neurofeedback in at least one cognitive domain. New interventions under consideration should be tested using placebo-controlled, double-blind experimental designs with follow-up evaluations.

Contributions of Cognitive Aging Models to the Explanation of Source Memory Decline across the Adult Lifespan.

Background: A number of cognitive aging models have been proposed to explain the age-related decline in several cognitive functions, but these models have rarely been examined together. We analyzed the contributions of four main models - processing resources, speed of processing, cognitive reserve and knowledge - to source memory decay related to the aging process.Methods: A total of 1554 healthy adults between 21 and 80 years old participated in the study. Structural equation modeling was conducted on data from the whole sample and separately in the data from young, middle-aged and older adult age groups. To estimate each cognitive model, we measured working memory discrimination levels (processing resources), working memory reaction times (speed of processing), education (cognitive reserve) and vocabulary (knowledge).Results: Processing resources mediate the effects of age on source memory across the adult lifespan, whereas speed of processing mediates these effects only in young adults, cognitive reserve only in middle-aged adults and knowledge only in older adults.Conclusions: Processing resources was the cognitive model that most contributes to explaining source memory decay. The fact that the other models are relevant to specific age groups provides useful information to exploit their benefits to preserve source memory in specific life stages.

Emotional context during encoding modulates recognition electrophysiological activity.

The aim of the study was to determine whether experiencing a non-emotional event in a positive or negative emotional context affected recognition of the event and the related electrophysiological activity. Twenty-eight adults participated in a betting-game task in which they could win (positive emotional context) or lose (negative emotional context) money. The participants also completed a non-betting task (non-emotional context). Afterward, the participants completed an old/new recognition task for faces with neutral expressions that were encoded during the betting and non-betting game. Event-related potentials and autonomic responses were recorded. The stimuli learned in the positive emotional context were better recognized than those learned in the non-emotional context. The FN400, the parietal old/new effect and the late frontal old/new effect were modulated by positive valence. Learning information under a positive emotional condition enhances its later recognition and the brain activity that underlies this process.

Neurophysiological responses during the binding process in working memory.

Working memory is a limited-capacity system responsible for handling and temporarily maintaining information. The multicomponent model of working memory includes the episodic buffer, which encodes, retains, and integrates multimodal information from the visuospatial sketchpad and the phonological loop. Although the model is highly accepted, little research has been conducted to examine the binding process in working memory. This research aimed to examine the neurophysiological similarities and differences among three different types of bindings: verbal-verbal, visual-visual, and verbal-visual. Event-related potentials (ERPs) were recorded in 30 participants while two pairs of stimuli from the different types of bindings were presented followed by a single pair. Participants indicated whether the single pair was equal to one of the previous two pairs, even if the stimulus position was changed, or was not equal to any of them. Compared with crossmodal binding, unimodal binding enhanced the amplitude of the positive slow wave (PSW) during encoding and of the P300 component and PSW during retrieval. These ERPs have been linked to processes such as stimulus classification and association mechanisms. The present study demonstrated that different amounts of resources or underlying processes are required for crossmodal bindings than for unimodal bindings within working memory.

Brain connectivity changes associated with episodic recollection decline in aging: A review of fMRI studies.

With advancing age, individuals experience a gradual decline in recollection, the ability to retrieve personal experiences accompanied by details, such as temporal and spatial contextual information. Numerous studies have identified several brain regions that exhibit age-related activation differences during recollection tasks. More recently, an increasing number of studies have provided evidence regarding how brain connectivity among the regions supporting recollection contributes to the explanation of recollection deficits in aging. However, brain connectivity evidence has not been examined jointly to provide an integrative view of how these new findings have improved our knowledge of the neurofunctional changes underlying the recollection deficits associated with aging. Therefore, the aim of the present study was to examine functional magnetic resonance imaging (fMRI) studies that employed one of the numerous methods available for analyzing brain connectivity in older adults. Only studies that applied connectivity analysis to data recorded during episodic recollection tasks, either during encoding or retrieval, were assessed. First, the different brain connectivity analysis methods and the information conveyed were briefly described. Then, the brain connectivity findings from the different studies were described and discussed to provide an integrative point of view of how these findings explain the decline in recollection associated with aging. The studies reviewed provide evidence that the hippocampus consistently decreased its connectivity with the parahippocampal gyrus and the posterior cingulate cortex, essential regions of the recollection network, in older adults relative to young adults. In addition, older adults exhibited increased connectivity between the hippocampus and several widespread regions compared to young adults. The increased connectivity was interpreted as brain intensification recourse to overcome recollection decay. Additionally, suggestions for future research in the field are outlined.

Effects of aging on interference control in selective attention and working memory.

Working memory decay in advanced age has been attributed to a concurrent decrease in the ability to control interference. The present study contrasted a form of interference control in selective attention that acts upon the perception of external stimuli (access) with another form that operates on internal representations in working memory (deletion), in order to determine both of their effects on working memory efficiency in younger and older adults. Additionally, we compared memory performance under these access and deletion functions to performance in their respective control conditions. The results indicated that memory accuracy improved in both age groups from the access functions, but that only young adults benefited from the deletion functions. In addition, intrusion effects in the deletion condition were larger in older than in younger adults. The ability to control the irrelevant perception- and memory-elicited interference did not decline in general with advancing age; rather, the control mechanisms that operate on internal memory representations declined specifically.

Influence of Dietary Nutrient Intake on Episodic Memory Across the Adult Life Span.

The aim of the study was to identify nutrients that have the ability to impact brain functioning and, as a consequence, influence episodic memory. In particular, we examined recollection, the ability to recall details of previous experiences, which is the episodic memory process most affected as age advances. A sample of 1,550 healthy participants between 21 and 80 years old participated in the study. Nutritional intake was examined through a food frequency questionnaire and software developed to determine the daily consumption of 64 nutrients based on food intake during the last year. Recollection was measured through a computerized source memory paradigm. First, we identified which nutrients influence recollection across the entire adult life span. Then, moderator analyses were conducted by dividing the sample into young (21-40 years old), middle-aged (41-60 years old) and older (61-80 years old) adults to establish in which life stage nutrients influence episodic memory. Across the adult life span, recollection accuracy was shown to benefit from the intake of sodium, heme, vitamin E, niacin, vitamin B6, cholesterol, alcohol, fat, protein, and palmitic, stearic, palmitoleic, oleic, gadoleic, alpha-linoleic and linoleic acid. The effects of energy, maltose, lactose, calcium and several saturated fatty acids on recollection were modulated by age; in older adults, the consumption of these nutrients negatively influenced episodic memory performance, and in middle-aged adults, only lactose had negative effects. Several brain mechanisms that support episodic memory were influenced by specific nutrients, demonstrating the ability of food to enhance or deteriorate episodic memory.

EEG power spectral measurements comparing normal and "thatcherized" faces.

In this paper we have made a broadband analysis to detect the electroencephalogram (EEG) frequencies that change selectively during the presentation of normal and "thatcherized" faces. Referential recordings to linked ears were obtained in 21 leads in 48 right-handed healthy male volunteers. Increase of delta power (1.75-3.91 Hz) was observed, related to the detection of distortion in faces at bifrontal and left temporoparietal cortex. The other bands had no contribution, when normal and modified faces were compared. These results support our hypothesis that a change in EEG power spectral may be related to discrimination between normal and thatcherized faces.

[Anxiety and depression in Mexican smokers, and their relationship with the severity of addiction]. / Ansiedad y depresión en fumadores mexicanos y su relación con el grado de adicción.

OBJECTIVE: To determine the relationship between the degree of addiction (DA) and pattern of tobacco consumption (PTC) with anxiety and depression in smokers who want to quit smoking. MATERIAL AND METHODS: At admission to a smoking cessation program 495 smokers were surveyed to determine anxiety (IDARE Test), depression (Beck Inventory Test), DA (Fagerström Test) and PTC (pack-years). RESULTS: DA ≥ 6 points was associated with high anxiety levels RM=1.94, (IC95%1.02-3.72), p<0.04]; and with symptoms of severe depression; [RM=2.24, (IC95%1.00-4.99), p<0.04)]. The PCT equal or greater than 21 pack-year, was associated with moderate anxiety; [RM=3.19 (IC95%1.94-5.25), p<.00]; high anxiety; [RM=3.36 (IC95% 1.66-6-80), p<.00]; with moderate depressive symptoms; [RM=3.14, (IC95% 1.75-5-62), p<.00] and severe depressive symptoms; [RM=9.85, (IC95% 3.30-29.37), p<.00)]. CONCLUSION: A significant association exists in smokers having high GA and PCT, with moderate and high anxiety and depressive symptoms that should be considered during interventions to quit.

Predictors of Working Memory Maintenance and Decline in Older Adults.

The aging process is associated with the gradual decline of several cognitive functions, and working memory is particularly affected. Although the majority of older adults experience a deterioration of their working memory, some individuals maintain their working memory in older age, and some suffer an extreme deterioration of their working memory. The purpose of the present study was to identify, among a total of 120 potential predictors, those that significantly contributed to these two extreme outcomes in working memory. A sample of 588 healthy adults was examined with the n-back task in the spatial and verbal domains using a 2-back level of difficulty. Individuals were classified as working memory maintainers or decliners if their discrimination level in the two domains was superior to the 80th percentile or inferior to the 20th percentile, respectively. Logistic regression identified eight and six significant predictors of working memory maintenance and decline, respectively. High vocabulary scores and smoking more were significant predictors of working memory maintenance; however, in the opposite direction, these same variables predicted working memory decline. Several consumption habits that influenced cerebrovascular function were found in both models. Psychological traits and everyday activities were present in both models. We identified specific predictors that contribute to extremely high or low working memory performance in older age.

Episodic memory decay along the adult lifespan: a review of behavioral and neurophysiological evidence.

The ability to learn and remember new information declines along life. Empirical evidence reveals that this deficit occurs unevenly with different types of memory. Episodic memory, which is referred to as the ability to remember our own experiences in a determined temporal and spatial context, is especially vulnerable to aging. Episodic information can be retrieved with or without the context information that took place when the episodic event was encoded. There is agreement that, with advancing age, the source information related to an episodic event is more susceptible to be forgotten than the event; however, there is no consensus regarding the age at which this decline begins, the speed of source-memory decline along life or the possible changes, due to aging, in neurophysiological activity during encoding of source information that is subsequently correctly retrieved. In an attempt to answer the first two issues, a behavioral study with 552 subjects from 20 to 80 years of age was conducted, which provided evidence of the exact age at which source memory starts to decline and of the speed of this memory loss along life. To address the last question, event-related potentials were recorded while young and old adults encoded source information, to investigate whether older adults generate memory traces different from young adults during encoding.

Predictors of Source Memory Success and Failure in Older Adults.

Source memory decline has been identified as one of the types of memory most seriously affected during older age. It refers to our capacity to recollect the contextual information in which our experiences take place. Although most elderly adults will be affected by progressive source memory decline, a subset of individuals will not follow this average pattern; instead, their source memory capabilities will remain functional. Likewise, a minority of individuals will manifest an extreme decay of their source memory abilities. The objective of the present study was to identify among 120 potential predictors that significantly contributed to these two extreme source memory outcomes. Spatial source memory was measured in a sample of 519 healthy individuals between 61 and 80 years old. Individuals who performed below the 20th and above the 80th percentiles in the source memory task were defined as individuals whose episodic memory failed and succeeded, respectively. Logistic models identified five and six significant predictors of source memory success and failure in older age, respectively. High source memory performance was mainly predicted by healthy cardiovascular markers and psychological traits, whereas low source memory performance was primarily predicted by consumption habits and by less engagement in mental activities. The models identified relevant biological and life experiences that underlie these unusual source memory outcomes in older age.

Mediators of episodic memory decay across the adult life span.

The ability to remember the details of our own experiences declines gradually as we get old. The reason for this decay has been attributed to several factors besides age, such as education, nutrient intake and health status. However, the influence of these factors has mainly been examined individually and rarely together. Here we identify those factors that jointly act as mediators of episodic memory decay across the adult life span. We examined source memory in a lifespan sample of 1557 healthy adults. A total of 70 physical, biological and lifestyle variables were measured and introduced into a structural equation model as potential mediators that intervene between age and source memory. Only 14 mediator variables reliably mediated source memory decay; notably, eight of these variables have an effect on the cardiovascular system. The model unequivocally highlights that the mediators that may impair cardiovascular functioning also impact brain resources involved in episodic memory. We identified the factors that are relevant to episodic memory decline when they interact together as occurs in real life.

Factors that positively or negatively mediate the effects of age on working memory across the adult life span.

Working memory abilities significantly decrease with advancing age; hence, the search for factors that may increase or mitigate this decline is critical. Several factors have been identified that influence working memory; however, their effects have been mainly assessed separately and rarely together with other factors in the same sample. We examined 120 variables to search for factors that jointly act as mediators of working memory decay across the adult life span. A sample of 1652 healthy adults was assessed in spatial and verbal working memory domains. Structural equation modeling analyses were conducted to search for potential mediators that intervened between age and working memory. Only 14 and 10 variables reliably mediated spatial and verbal working memory, respectively. Factors from several domains remained in the models, such as individual characteristics, physiological traits, consumption habits, and regular activities. These factors are sufficiently powerful to influence working memory decline when they jointly interact, as in everyday living.