Working memory maintenance contributes to long-term memory formation: Evidence from slow event-related brain potentials

Behavioral research has led to conflicting views regarding the relationship between working memory (WM) maintenance and long-term memory (LTM) formation. We used slow event-related brain potentials to investigate the degree to which neural activity during WM maintenance is associated with successful LTM formation. Participants performed a WM task with objects and letter strings, followed by a surprise LTM test. Slow potentials were found to be more negative over the parietal and occipital cortex for objects and over the left frontal cortex for letter strings during WM maintenance. Within each category, they were enhanced for items that were subsequently successfully remembered. These effects were topographically distinct, with maximum effects at those electrodes that showed the maximum negativity during WM maintenance in general. Together, these results are strongly consistent with the ideas that WM maintenance contributes to LTM formation and that this may occur through strengthening of stimulus-specific cortical memory traces.     

Assessing team performance: Moderating roles of transactive memory,hypercompetition, and emotional regulation

This study proposes a model based on transactive memory theory to analyze team performance. In the proposed model, team performance is influenced by hypercompetition and emotional regulation directly and indirectly via the mediation of transactive memory and knowledge sharing. According to the model, the direct effect of knowledge sharing on team performance is moderated by both hypercompetition and emotional regulation. Empirical testing of this model, using team personnel in banking, insurance, and financing firms, confirmed the applicability of the transactive memory theory among these service firms’ work teams. Managerial implications and research limitations are discussed.     

Generativity in multiple roles

Interest in the Eriksonian notion of generativity and its role in the lives of mature adults has recently increased. In the present study, we examined generativity separately in the roles of wife, worker, and mother, and examined the utility of our strategy relative to more global measurement strategies in explaining variation in well-being. Two samples of employed mothers were studied, one sample employed in private industry and the other in a university setting. Statistical analyses demonstrated that measurement equivalence existed across the two samples (i.e., that the patterns and magnitudes of factor loadings did not differ significantly). For 8 of 11 indices of well-being examined across the two samples, role-specific measures of generativity explained significantly greater variation than did global measures.     

Temporal dynamics of Arc gene induction in hippocampus: relationship to context memory formation

Past studies have proposed a role for the hippocampus in the rapid encoding of context memories. Despite this, there is little data regarding the molecular processes underlying the stable formation of a context representation that occurs in the time window established through such behavioral studies. One task that is useful for investigating the rapid encoding of context is contextual fear conditioning (CFC). Behavioral studies demonstrate that animals require approximately 30 s of exploration prior to a footshock to form a contextual representation supporting CFC. Thus, any potential molecular process required for the stabilization of the cellular representation for context must be activated within this narrow and behaviorally defined time window. Detection of the immediate-early gene Arc presents an ideal method to assess the activation of specific neuronal ensembles, given past studies showing the context specific expression of Arc in CA3 and CA1 subfields and the role of Arc in hippocampal long-term synaptic plasticity. Therefore, we examined the temporal dynamics of Arc induction within the hippocampus after brief context exposure to determine whether experience-dependent Arc expression could be involved in the rapid encoding of incidental context memories. We found that the duration of context exposure differentially activated Arc expression in hippocampal subfields, with CA3 showing rapid engagement within as little as 3 s of exposure. By contrast, Arc induction in CA1 required 30 s of context exposure to reach maximal levels. A parallel behavioral experiment revealed that 30 s, but not 3 s, exposure to a context resulted in strong conditioned freezing 24 h later, consistent with past studies from other laboratories. The current study is the first to examine the rapid temporal dynamics of Arc induction in hippocampus in a well-defined context memory paradigm. These studies demonstrate within 30 s of context exposure Arc is fully activated in CA3 and CA1, suggesting that the engagement of plastic processes requiring Arc function (such as long-term potentiation) occurs within the same temporal domain as that required for behavioral conditioning.     

Adding elder care to women's multiple roles: A critical review of the caregiver stress and multiple roles literatures

Sex Roles - Research on the effect of multiple roles on women's well-being has focused almost exclusively on the employment and child rearing roles of younger women, and has overlooked the...     

Decisions and the evolution of memory: multiple systems, multiple functions

Memory evolved to supply useful, timely information to the organism's decision-making systems. Therefore, decision rules, multiple memory systems, and the search engines that link them should have coevolved to mesh in a coadapted, functionally interlocking way. This adaptationist perspective suggested the scope hypothesis: When a generalization is retrieved from semantic memory, episodic memories that are inconsistent with it should be retrieved in tandem to place boundary conditions on the scope of the generalization. Using a priming paradigm and a decision task involving person memory, the authors tested and confirmed this hypothesis. The results support the view that priming is an evolved adaptation. They further show that dissociations between memory systems are not--and should not be--absolute: Independence exists for some tasks but not others.     

Temporal memory over the adult lifespan

Performances of noncollege student young adults, middle-aged adults, and elderly adults were contrasted on word temporal memory and paired-associate learning tasks. A comparison group of college-student subjects was also evaluated on each task. Significant effects for age variation were found for each task. The age sensitivity for temporal memory conflicts with one of the criteria commonly established for determining the automaticity of a memory task. In addition, moderately high positive correlations were found for each age group between word temporal memory scores and paired-associate learning scores, implying the involvement of effortful processes over the adult lifespan in word temporal memory.     

Mood congruent memory in dysphoria: the roles of state affect and cognitive style

Biases in incidental memory for self-referent adjectives and intentional memory were compared across nondysphoric (ND; n=48), experimentally induced dysphoric (EXP; n=49), and naturally dysphoric (NAT; n=48) individuals. Negative biases, "evenhandedness", and positive biases were demonstrated among NAT, EXP and ND participants, respectively, in terms of incidental memory. Correlation analyses suggested that the effects of cognitive style (self-esteem, dysfunctional attitudes, and attributional style) are limited to negative stimuli. Memory for incidental positive stimuli was only predicted by state affect. Groups did not differ in performance on an intentional memory task. Implications for network and schema models of depression are explored.     

Hebb repetition effects in visual memory: the roles of verbal rehearsal and distinctiveness

A version of the Hebb repetition task was used with faces to explore the generality of the effect in a nonverbal domain. In the baseline condition, a series of upright faces was presented, and participants were asked to reconstruct the original order. Performance in this condition was compared to another in which the same stimuli were accompanied by concurrent verbal rehearsal to examine whether Hebb learning is dependent on verbal processing. Baseline performance was also compared to a condition in which the same faces were presented inverted. This comparison was used to determine the importance in Hebb learning of being able to visually distinguish between the list items. The results produced classic serial position curves that were equivalent over conditions with Hebb repetition effects being in evidence only for upright faces and verbal suppression as having no effect. These findings are interpreted as posing a challenge to current models derived from verbal-domain data.     

Plasticity of nonneuronal brain tissue: roles in developmental disorders

Neuronal and nonneuronal plasticity are both affected by environmental and experiential factors. Remodeling of existing neurons induced by such factors has been observed throughout the brain, and includes alterations in dendritic field dimensions, synaptogenesis, and synaptic morphology. The brain loci affected by these plastic neuronal changes are dependent on the type of experience and learning. Increased neurogenesis in the hippocampal dentate gyrus is a well-documented response to environmental complexity ("enrichment") and learning. Exposure to challenging experiences and learning opportunities also alters existing glial cells (i.e., astrocytes and oligodendrocytes), and up-regulates gliogenesis, in the cerebral cortex and cerebellum. Such glial plasticity often parallels neuronal remodeling in both time and place, and this enhanced morphological synergism may be important for optimizing the functional interaction between glial cells and neurons. Aberrant structural plasticity of nonneuronal elements is a contributing factor, as is aberrant neuron plasticity, to neurological and developmental disorders such as epilepsy, autism, and mental retardation (i.e., fragile X syndrome). Some of these nonneuronal pathologies include abnormal cerebral and cerebellar white matter and myelin-related proteins in autism; abnormal myelin basic protein in fragile X syndrome (FXS); and abnormal astrocytes in autism, FXS, and epilepsy. A number of recent studies demonstrate the possibility of using environmental and experiential intervention to reduce or ameliorate some of the neuronal and nonneuronal abnormalities, as well as behavioral deficits, present in these neurological and developmental disorders.     

A fresh look at an ancient receptor family: emerging roles for low density lipoprotein receptors in synaptic plasticity and memory formation

The well-known family of low-density lipoprotein receptors represents a collection of ancient membrane receptors that have been remarkably conserved throughout evolution. These multifunctional receptors, known to regulate cholesterol transport, are becoming increasingly interesting to the neuroscience community due to their ability to transduce a diversity of extracellular signals across the membrane in the adult CNS. Their roles in modulating synaptic plasticity and necessity in hippocampus-specific learning and memory have recently come to light. In addition, genetic, biochemical and behavioral studies have implicated these signaling systems in a number of human neurodegenerative and neuropsychiatric disorders involving loss of cognitive ability, such as Alzheimer's disease, schizophrenia and autism. This review describes the known functions of these receptors and discusses their potential role in processes of synaptic regulation and memory formation.     

Working memory and arithmetic calculation in children: the contributory roles of processing speed, short-term memory, and reading

The cognitive underpinnings of arithmetic calculation in children are noted to involve working memory; however, cognitive processes related to arithmetic calculation and working memory suggest that this relationship is more complex than stated previously. The purpose of this investigation was to examine the relative contributions of processing speed, short-term memory, working memory, and reading to arithmetic calculation in children. Results suggested four important findings. First, processing speed emerged as a significant contributor of arithmetic calculation only in relation to age-related differences in the general sample. Second, processing speed and short-term memory did not eliminate the contribution of working memory to arithmetic calculation. Third, individual working memory components--verbal working memory and visual-spatial working memory--each contributed unique variance to arithmetic calculation in the presence of all other variables. Fourth, a full model indicated that chronological age remained a significant contributor to arithmetic calculation in the presence of significant contributions from all other variables. Results are discussed in terms of directions for future research on working memory in arithmetic calculation.     

Differential regulation of glutamic acid decarboxylase gene expression after extinction of a recent memory vs. intermediate memory

Extinction reduces fear to stimuli that were once associated with an aversive event by no longer coupling the stimulus with the aversive event. Extinction learning is supported by a network comprising the amygdala, hippocampus, and prefrontal cortex. Previous studies implicate a critical role of GABA in extinction learning, specifically the GAD65 isoform of the GABA synthesizing enzyme glutamic acid decarboxylase (GAD). However, a detailed analysis of changes in gene expression of GAD in the subregions comprising the extinction network has not been undertaken. Here, we report changes in gene expression of the GAD65 and GAD67 isoforms of GAD, as measured by relative quantitative real-time RT-PCR, in subregions of the amygdala, hippocampus, and prefrontal cortex 24-26 h after extinction of a recent (1-d) or intermediate (14-d) fear memory. Our results show that extinction of a recent memory induces a down-regulation of Gad65 gene expression in the hippocampus (CA1, dentate gyrus) and an up-regulation of Gad67 gene expression in the infralimbic cortex. Extinguishing an intermediate memory increased Gad65 gene expression in the central amygdala. These results indicate a differential regulation of Gad gene expression after extinction of a recent memory vs. intermediate memory.     

Individual differences in emotional memory: adult attachment and long-term memory for child sexual abuse

In the present study, attachment-related differences in long-term memory for a highly emotional life event, child sexual abuse (CSA), were investigated. Participants were 102 documented CSA victims whose cases were referred for prosecution approximately 14 years earlier. Consistent with the proposal that avoidant individuals defensively regulate the processing of potentially distressing information (Bowlby, 1980), attachment avoidance was negatively associated with memory for particularly severe CSA incidents. This finding was not mediated by the extent to which participants reported talking about the abuse after it occurred, although post abuse discussion did enhance long-term memory. In addition, accuracy was positively associated with maternal support following the abuse and extent of CSA-related legal involvement. Attachment anxiety was unrelated to memory accuracy, regardless of abuse severity. Implications of the findings for theories of avoidant defensive strategies and emotional memory are discussed.     

Investigating the roles of phonological and semantic memory in sentence recall

The mechanisms underlying short-term sentence recall have been the subject of recent investigations. While both semantic and phonological information have been found to play a role in sentence recall, this has been established using different paradigms in previous research. As a result, it is not clear whether the contributions of semantic and phonological information are equivalent subject only to specific experimental conditions. The present study used a common paradigm with equally plausible lures to systematically compare the roles of semantic and phonological information in short-term sentence recall. The lure intrusion paradigm was used with three different lures that were all equally plausible in the context of the sentence: semantic, onset, and rhyme. Further, no contextual cues were provided in the sentence to bias the participant. The findings indicate that there were significantly more semantic and onset intrusions compared to rhyme intrusions. This is interpreted in light of models incorporating lexical information during sentence production.     

Investigating the roles of phonological and semantic memory in sentence recall

The mechanisms underlying short-term sentence recall have been the subject of recent investigations. While both semantic and phonological information have been found to play a role in sentence recall, this has been established using different paradigms in previous research. As a result, it is not clear whether the contributions of semantic and phonological information are equivalent subject only to specific experimental conditions. The present study used a common paradigm with equally plausible lures to systematically compare the roles of semantic and phonological information in short-term sentence recall. The lure intrusion paradigm was used with three different lures that were all equally plausible in the context of the sentence: semantic, onset, and rhyme. Further, no contextual cues were provided in the sentence to bias the participant. The findings indicate that there were significantly more semantic and onset intrusions compared to rhyme intrusions. This is interpreted in light of models incorporating lexical information during sentence production.     

Interference in memory for multiple contexts

Remembering that an item occurred in several different lists is formulated here in terms of retrieval of corresponding list tags associated to the item. Therefore, associative interference should operate upon remembering the several list contexts in which an item appeared. Experimental Ss studied four (or five) overlapping lists of 16 words, sampled from a master set of 32 words, with a given word exemplifying one of the 2 4 (or 2s 5 ) possible sequences of appearances and nonappearances over the four (or five) lists. Later Ss rated from memory for each word and for each list whether that word had occurred in that list. After correcting for interlist generalization effects, indices of discriminative memory revealed strong proactive interference and weaker retroactive interference. Discriminative memory that an item occurred in a given list was poorer the more prior or more subsequent lists in which that item had also occurred. Thus, list differentiation appears explicable in terms of item-specific associative interference.