EEG oscillations during sleep and dream recall. State- or trait-like individual differences?

Dreaming represents a peculiar form of cognitive activity during sleep. On the basis of the well-known relationship between sleep and memory, there has been a growing interest in the predictive role of human brain activity during sleep on dream recall. Neuroimaging studies indicate that rapid eye movement (REM) sleep is characterized by limbic activation and prefrontal cortex deactivation. This pattern could explain the presence of emotional contents in dream reports. Furthermore, the morphoanatomical measures of amygdala and hippocampus predict some features of dream contents (bizarreness, vividness, and emotional load). More relevant for a general view of dreaming mechanisms, empirical data from neuropsychological and electroencephalographic (EEG) studies support the hypothesis that there is a sort of continuity between the neurophysiological mechanisms of encoding and retrieval of episodic memories across sleep and wakefulness. A notable overlap between the electrophysiological mechanisms underlying emotional memory formation and some peculiar EEG features of REM sleep has been suggested. In particular, theta (5–8 Hz) EEG oscillations on frontal regions in the pre-awakening sleep are predictive of dream recall, which parallels the predictive relation during wakefulness between theta activity and successful retrieval of episodic memory. Although some observations support an interpretation more in terms of an intraindividual than interindividual mechanism, the existing empirical evidence still precludes from definitely disentangling if this relation is explained by state- or trait-like differences

Analysis of Internally Bandlimited Multistage Cubic-Term Generators for RF Receivers

Adaptive feedforward error cancellation applied to correct distortion arising from third-order nonlinearities in RF receivers requires low-noise low-power reference cubic nonidealities. Multistage cubic-term generators utilizing cascaded nonlinear operations are ideal in this regard, but the frequency response of the interstage circuitry can introduce errors into the cubing operation. In this paper, an overview of the use of cubic-term generators in receivers relative to other applications is presented. An interstage frequency response plan is presented for a receiver cubic-term generator and is shown to function for arbitrary three-signal third-order intermodulation generation. The noise of such circuits is also considered and is shown to depend on the total incoming signal power across a particular frequency band. Finally, the effects of the interstage group delay are quantified in the context of a relevant communication standard requirement

The impact of secondary tasks on multitasking in a virtual environment

One experiment is described that examined the possible involvement of working memory in the Virtual Errands Test (McGeorge et al., 2000), which requires participants to complete errands within a virtual environment, presented on a computer screen. Time was limited, therefore participants had to swap between tasks (multitask) efficiently to complete the errands. Forty-two undergraduates participated, all attempting the test twice. On one of these occasions they were asked to perform a concurrent task throughout (order of single and dual task conditions was counterbalanced). The type of secondary task was manipulated between-groups. Twenty-one participants were asked to randomly generate months of the year aloud in the dual-task condition, while another twenty-one were asked to suppress articulation by repeating the word “December”. An overall dual-task effect on the virtual errands test was observed, although this was qualified by an interaction with the order of single and dual task conditions. Analysis of the secondary task data showed a drop in performance (relative to baseline) under dual-task conditions, and that drop was greater for the random generation group and the articulatory suppression group. These data are interpreted as suggesting that the central executive and phonological loop components of working memory are implicated in this test of multitasking

Individual differences in updating information during reading

Causal information has been shown to help readers update outdated information (Rapp and Kendeou, 2007, 2009). Outdating occurs when integrating new information produces a conflict with encoded information that was encountered earlier in the text. There are also a number of individual differences among readers that influence how successful they will be at encoding, integrating, and outdating information including their reading skill, working memory capacity, and domain knowledge. This thesis examines how these individual differences impact how readers utilize causal information during updating. Across three experiments, participants were indexed as less-skilled or skilled readers using the Gates-MacGinitie Reading Test. Experiments 1 and 2 showed that skilled readers used causal information to update their representation of the text while less-skilled readers continued to show disruption from outdated information. The findings are examined in the discussion section

The availability of inferences in children and young adults

Much of the research on age-related differences in the ability to inhibit irrelevant information in a given task has been on the study of younger and older adults. Only a minimal amount of research has focused on the developmental differences in children and young adults. Accordingly, the purpose of this paper is to examine whether age-related differences exist between children and young adults in processes consistent with inhibition. Third-, sixth-grade children, and college undergraduates listened to twenty-four garden path passages containing either expected or unexpected, but acceptable, conclusions. The twenty-four passages were divided into four subsets, with each subset containing six passages. Each of the six passages within a given subset consisted of a judgment task that contained either ten or fourteen words, as appropriate for a mid-point or an end-point testing of a passage. Participants were instructed to decide (yes or no) whether each test word was consistent with his or her understanding of the passage. Finally, each subset of six passages ended with the testing of the inference questions that corresponded to passages contained in that subset. Analyses revealed both groups of children to be less efficient than college students in the use of those attentional processes consistent with the inhibitory processes of selective attention that restrict access to and limit the maintenance of task-irrelevant information in working memory. Although children and adults showed equally strong tendencies to accept a target inference at the middle-test and end-test position, both groups of children were more likely than young adults to accept a competing, alternate interpretation of unexpected passages. The data reviewed here suggests developmental differences between children and young adults exist in the use of those processes required of inhibition that control the contents of working memory

Metacognition, proactive interference, and working memory : can people monitor for proactive interference at encoding and retrieval?

"The present study investigated whether subjects were sensitive to negative transfer and proactive interference (PI) at encoding and retrieval and whether sensitivity varied with working memory (WM) ability. Monitoring at encoding was assessed by having subjects make judgments of learning (JOLs; E1 & E2) or by controlling study time (E3) while learning word pairs. Monitoring at retrieval was assessed by dynamic prediction of knowing (DPOK) judgments. At encoding, the results suggest that subjects are sensitive to negative transfer at the list level but not the item level. At retrieval, subjects were sensitive to PI at the list level and sometimes at the item level. Sensitivity to negative transfer did not vary with WM, but sensitivity to PI did. Implications for control are discussed."--Abstract from author supplied metadata

Involuntary memories after stressor exposure: contribution of hormonal status and rumination in women.

Women experience fewer traumatic stressors over their lifespan than men, but demonstrate a higher prevalence of major depression and stressor-related disorders as a result of trauma exposure (Breslau & Anthony, 2007; Kessler et al., 2005). Differences in prevalence of stressor-related disorders may partially be due to sex-linked vulnerabilities related to emotional memory. Emotion assists in modulation of memory through neurological processes. This modulation enhances memory for emotional stimuli and can lead to a greater frequency of involuntary recall after stressor exposure. This involuntary memory is also a hallmark symptom of Posttraumatic Stress Disorder (PTSD). Sex-linked vulnerabilities, specifically hormonal status and frequency of brooding rumination may contribute to a higher prevalence of PTSD in women following stress exposure through their influence on emotional memory processes. The current study further examined these potential sex-linked vulnerabilities in 77 (43 hormonal contraceptive users and 34 naturally cycling) women. Participants were asked to report on their experience of involuntary memories each evening for seven days following exposure to a trauma analogue film. Contrary to hypotheses, neither hormonal contraceptive status nor brooding rumination were statistically significant predictors of involuntary memory frequency, related distress, or related activity interference during the seven day follow-up. Severity of depressive symptoms was the only statistically significant predictor in all tested models. Findings further highlight current depressive symptoms, as a robust vulnerability factor for developing intrusive memories following stressor exposure

The Role of Executive Control Deficits in Cognitive Correlates of Dysphoria

Recent research has suggested that deficits in executive control, especially impairments in cognitive inhibition, as well as rumination, negative involuntary memories, and reduced autobiographical memory specificity could play key roles in the development and exacerbation of depressive symptoms. In the present study, participants completed the Negative Affective Priming (NAP) task, the Ruminative Responses Scale (RRS), the Continuous Word Association Task (CWAT), the Autobiographical Memory Task (AMT), and the Center for Epidemiologic Studies Depression Scale Revised (CESD-R) to examine the relationship between deficits in executive control and dysphoria that may be mediated by ruminative thinking, negative involuntary memory retrieval, and autobiographical memory specificity. Executive control deficits and greater ruminative tendencies were found in the dysphoric sample relative to controls, although there was no evidence to support differences in involuntary memory retrieval or memory specificity. Furthermore, rumination, especially brooding rumination, was found to mediate the relationship between executive control deficits and dysphoria. Although the NAP task seems to measure some aspect of executive control, the results suggested that the task itself warrants further scrutiny

Physically emotional: the role of embodied emotions from encoding to memory

Theories of embodied cognition hold that the perception of an emotional stimulus can trigger a simulation of the correspondent state in the motor, somatosensory, and affective systems. Amongst other bodily reactions, it is thought that such embodied simulations are also reflected in facial expressions in accordance to the emotional connotation of the presented stimulus \u2013 a phenomenon also referred to as facial motor resonance. Chapter 1 reviews the theories of embodied cognition, in general, and facial motor resonance, in particular. The aim of the present thesis was to further define the function of embodied simulations, reconciling previous inconsistent results concerning the level at which embodied simulations affect the processing of emotional information, and to explore uncharted aspects of embodiment theories such as their role in memory for emotional information. In Chapter 2, I investigated the hypothesis that embodied simulations play a key role in processing only emotional information (happy and sad sentences and faces), which is low in emotional intensity or difficult to encode. This hypothesis was tested in a behavioral experiment involving a group of participants undergoing subcutaneous cosmetic injections of Botulinum Toxin-A (Botox) compared with a matched control group. The results confirmed the hypothesis: participants in the Botox group, but not those in the control group, rated emotional sentences and faces as less emotional after the Botox treatment. Furthermore, they were slower at identifying sad faces as sad after the treatment. The critical nuance of these findings was that only stimuli with moderate emotional intensity were affected. Upon considering the findings of Chapter 2, the question arose as to whether facial motor resonance, in addition to playing a role in the initial processing and recognition of emotional content, also determines its retrieval. This topic was investigated in the study reported in Chapter 3, in which eighty participants underwent a memory task for emotional and neutral words. The task consisted of an encoding and a retrieval phase. Facial muscles were blocked by a hardening facial mask in one of four conditions: during encoding, during retrieval, during both encoding and retrieval, or never (control). The results showed that memory for emotional words decreased significantly if embodiment was blocked at either point in time during the experiment (during encoding, during retrieval, or during both), in contrast to the control condition. These results suggest that facial motor resonance is involved in the encoding and retrieval of emotional words. In Chapter 4, this line of research was extended and applied to the processing of emotional content in a second language (L2). In a classical memory task involving an encoding and a retrieval phase, thirty-two Spanish/English late bilinguals were presented with emotional (happy and angry) and neutral words. Electromyographic (EMG) activity and skin conductance (SC) were recorded during the encoding phase. The results suggest that the emotionality of an L2 appears to be not only reduced as compared with a first language (L1), but also to be less embodied. This was suggested both by the absence of the Enhanced Emotional Memory (EEM) effect in L2 as well as by partially decreased and delayed EMG and SC activity in response to emotional words in L2 as compared with L1. If facial motor resonance is involved in the recollection of emotional information, what is its role in forgetting emotional information? This question was pursued in the study reported in Chapter 5, employing the directed forgetting paradigm (DF), which involves the presentation of a stimulus (e.g. a word), followed by a cue to \u201cremember\u201d (R-cue) or to \u201cforget\u201d (F-cue). Twenty-one participants were instructed to remember or to intentionally forget neutral, negative, and positive words. EMG from the zygomaticus and corrugator muscle was simultaneously recorded with event related potentials (ERPs). The behavioral results showed that both neutral and emotional words were forgotten at equal rates. However, the type of word and cue instruction interactively modulated facial motor resonance, as measured by EMG. Upon R-cues, the muscle activation patterns for both negative and positive word types were significantly enhanced, in contrast to the facial motor resonance evoked by F-cues. It was speculated that the increase in facial motor resonance reflects active rehearsal, whereas the decrease is associated to active suppression mechanisms. This assumption was supported by the ERP data, indicating that the successful forgetting of affective words required more active suppression, as was indexed by enhanced frontal positivities. In contrast, intentional encoding of emotional words followed by R-cues seemed to be facilitated by an enhanced P3 and late positive potential (LPP) components emerging from centro-parietal areas. These components have been hypothesized to reflect rehearsal and memory consolidation processes. Overall, the present results suggest that embodied simulations help with the processing of indefinite emotional information and assist with the formation of enduring representations of emotional stimuli. The implications of these findings for theories of embodied cognition, in general, and for emotion processing, in particular, are discussed in Chapter 6