Top-down modulation of memory under stress

It is widely accepted that stress enhances episodic memory. On a neurophysiological level, stress exposure results in the release of corticosteroids (mainly cortisol in humans) and catecholamines (most prominently noradrenaline), and this stress response generally enhances the formation and consolidation of episodic memory of the stressor (Schwabe et al., 2022). However, little is known about the underlying cognitive processes of memory under stress. One mechanism that appears to underly memory in general is attention. It has been known for decades, perhaps even centuries, that there is a tight link between attention and memory (Chun & Turk-Browne, 2007; Cowan et al., 2023). Lesion studies suggest that the posterior parietal cortex, a key area for selective attention (Behrmann et al., 2004), also affects episodic memory. Moreover, Uncapher et al. (2011) have shown that activity in the left medial intraparietal sulcus (left mIPS) elicited by a visuospatial cue predicted later recall success. In line with these findings (for a review see Kim, 2022), the attention to memory model (AtoM) suggests a key modulatory role of the dorsal parietal cortex (DPC) in top-down attentional effects on memory (Cabeza, 2008; Cabeza et al., 2008). Consequently, we expect superior memory for to-be-attended compared to to-be-unattended stimuli. Inhibition of the left mIPS via transcranial magnetic stimulation (TMS) is expected to abolish or at least weaken top-down attention effects on memory. But how could attention-to-memory effects relate to memory formation under stress? According to the arousal-biased competition theory (ABC, Mather & Sutherland, 2011), arousal (including stress) boosts this superior memory for to-be-attended compared to to-be-unattended stimuli (Lee et al., 2014; Lee et al., 2015). According to ABC theory, noradrenergic arousal increases neural gain, thereby allowing for enhanced encoding of attended (vs. unattended) stimulus material (Lee et al., 2014; Lee et al., 2015; Dunsmoor et al., 2022). As mentioned before, noradrenergic arousal in response to stress has also been indicated to enhance episodic memory. We therefore predict that the stress-induced enhancement of episodic memory formation is driven by noradrenergic arousal and modulated by attentional processes. We assume two potential underlying neurocognitive mechanisms for the link between attention and memory under stress. First, we expect participants to show a higher mnemonic difference between stimuli in the foreground compared to background scenes for to-be-attended compared to to-be-unattended stimuli, and this attentional bias should be enhanced by stress. To this end, we will assess fixation times using eye tracking. Second, we expect that stress results in higher post-encoding reactivation of to-be-attended compared to to-be-unattended stimuli. Reactivation refers to the reoccurrence of neural patterns present at encoding and has previously been related to memory consolidation (Tambini et al., 2010; Tambini & Davachi, 2013). To this end, we will use electrophysiological data assessed via electroencephalography (EEG). To summarize: Stress enhances the episodic memory of an event. Since there is a tight link between attention and memory, we hypothesize that attention modulates the effects of stress on memory. In line with the ABC theory, we further expect stress to enhance the memory difference between to-be-attended and to-be-unattended stimuli, driven by stress-enhanced post-encoding reactivation of to-be-attended stimuli and a stress-enhanced attentional bias in fixation times. We will integrate an encoding task into the Trier Social Stress Test (TSST; Kirschbaum et al., 1993). Specifically, participants will be instructed by a cold and non-reinforcing TSST committee to attend to one stimulus category (e.g., fruits) but not the other (e.g., stationery). Memory performance will be assessed 24h later using a free recall and a recognition task. Our parameters for (nor)adrenergic arousal will be pupil dilation, skin conductance responses (SCR), and blood pressure. We will also measure salivary cortisol. To assess the role of the left mIPS in top-down attention and its potential modulatory role in memory under stress, we will transiently inhibit the left mIPS using TMS. To assess our main research questions, we will compare foreground-background fixation times between to-be attended and to-be-unattended stimuli. Finally, to test for stress-related enhancements of post-encoding reactivation of to-be-attended stimuli, we will train a classifier on our EEG data and decode post-encoding reactivation using multivariate pattern analysis (MVPA)

Top-down modulation of memory under stress

It is widely accepted that stress enhances episodic memory. On a neurophysiological level, stress exposure results in the release of corticosteroids (mainly cortisol in humans) and catecholamines (most prominently noradrenaline), and this stress response generally enhances the formation and consolidation of episodic memory of the stressor (Schwabe et al., 2022). However, little is known about the underlying cognitive processes of memory under stress. One mechanism that appears to underly memory in general is attention. It has been known for decades, perhaps even centuries, that there is a tight link between attention and memory (Chun & Turk-Browne, 2007; Cowan et al., 2023). Lesion studies suggest that the posterior parietal cortex, a key area for selective attention (Behrmann et al., 2004), also affects episodic memory. Moreover, Uncapher et al. (2011) have shown that activity in the left medial intraparietal sulcus (left mIPS) elicited by a visuospatial cue predicted later recall success. In line with these findings (for a review see Kim, 2022), the attention to memory model (AtoM) suggests a key modulatory role of the dorsal parietal cortex (DPC) in top-down attentional effects on memory (Cabeza, 2008; Cabeza et al., 2008). Consequently, we expect superior memory for to-be-attended compared to to-be-unattended stimuli. Inhibition of the left mIPS via transcranial magnetic stimulation (TMS) is expected to abolish or at least weaken top-down attention effects on memory. But how could attention-to-memory effects relate to memory formation under stress? According to the arousal-biased competition theory (ABC, Mather & Sutherland, 2011), arousal (including stress) boosts this superior memory for to-be-attended compared to to-be-unattended stimuli (Lee et al., 2014; Lee et al., 2015). According to ABC theory, noradrenergic arousal increases neural gain, thereby allowing for enhanced encoding of attended (vs. unattended) stimulus material (Lee et al., 2014; Lee et al., 2015; Dunsmoor et al., 2022). As mentioned before, noradrenergic arousal in response to stress has also been indicated to enhance episodic memory. We therefore predict that the stress-induced enhancement of episodic memory formation is driven by noradrenergic arousal and modulated by attentional processes. We assume two potential underlying neurocognitive mechanisms for the link between attention and memory under stress. First, we expect participants to show a higher mnemonic difference between stimuli in the foreground compared to background scenes for to-be-attended compared to to-be-unattended stimuli, and this attentional bias should be enhanced by stress. To this end, we will assess fixation times using eye tracking. Second, we expect that stress results in higher post-encoding reactivation of to-be-attended compared to to-be-unattended stimuli. Reactivation refers to the reoccurrence of neural patterns present at encoding and has previously been related to memory consolidation (Tambini et al., 2010; Tambini & Davachi, 2013). To this end, we will use electrophysiological data assessed via electroencephalography (EEG). To summarize: Stress enhances the episodic memory of an event. Since there is a tight link between attention and memory, we hypothesize that attention modulates the effects of stress on memory. In line with the ABC theory, we further expect stress to enhance the memory difference between to-be-attended and to-be-unattended stimuli, driven by stress-enhanced post-encoding reactivation of to-be-attended stimuli and a stress-enhanced attentional bias in fixation times. We will integrate an encoding task into the Trier Social Stress Test (TSST; Kirschbaum et al., 1993). Specifically, participants will be instructed by a cold and non-reinforcing TSST committee to attend to one stimulus category (e.g., fruits) but not the other (e.g., stationery). Memory performance will be assessed 24h later using a free recall and a recognition task. Our parameters for (nor)adrenergic arousal will be pupil dilation, skin conductance responses (SCR), and blood pressure. We will also measure salivary cortisol. To assess the role of the left mIPS in top-down attention and its potential modulatory role in memory under stress, we will transiently inhibit the left mIPS using TMS. To assess our main research questions, we will compare foreground-background fixation times between to-be attended and to-be-unattended stimuli. Finally, to test for stress-related enhancements of post-encoding reactivation of to-be-attended stimuli, we will train a classifier on our EEG data and decode post-encoding reactivation using multivariate pattern analysis (MVPA)

The effect of mindfulness-based interventions on telomere length and telomerase activity: A systematic review and meta-analysis

Systematic review and meta-analysis of the effect of mindfulness-based interventions on telomere length and telomerase activit

The effect of mindfulness-based interventions on telomere length and telomerase activity: A systematic review and meta-analysis

Systematic review and meta-analysis of the effect of mindfulness-based interventions on telomere length and telomerase activit

The Effects of Mindfulness-Based Interventions on Telomere Length and Telomerase Activity: A Systematic Review and Meta-Analysis

Abstract Objectives Previous meta-analyses suggested that mindfulness-based interventions (MBIs) may have beneficial effects on telomere length (TL) and telomerase activity (TA), two biological markers of cellular aging and cell stress. The present review aimed to provide the most comprehensive synthesis of the available evidence to date and tested a number of important effect moderators. Method Twenty-five studies (18 RCTs, 1 RCT and cohort study, 6 non-randomized studies) with 2099 participants in total were obtained with a systematic literature search, 10 studies had not been included in any previous meta-analysis. Effect sizes were aggregated with random-effects models, the risk of bias was evaluated with standardized checklists, and the most influential moderators were identified with a machine-learning approach. Results On average, MBIs had small-to-medium effects on TL (g = 0.23, 95% CI = [0.07, 0.39], p = 0.006) and TA (g = 0.37 [0.01, 0.73], p = 0.046), which, however, were driven by retrospective case–control studies with experienced meditators (TL) and by studies without control interventions and studies from Asia (TA). Most studies had an unclear risk of bias and low analytic power, and there was an indication of publication bias among the TL studies. Conclusions TL may not be a useful outcome to assess the efficacy of common MBIs. Effects on TA were smaller than previously assumed and may not be specific for MBIs; TA likely is increased by other active interventions as well. More high-quality and high-powered studies, which also apply open-science practices, are needed to move the field forward. </jats:sec

Confirming pupil dilation as physiological marker of Bayesian inference in dynamic auditory localization

Bayesian theory has been applied successfully to explain human perception in noisy and volatile environments. Previous studies used explicit predictive-inference tasks to show that responses of the pupil-linked arousal system correlate with the weighting of prior knowledge during high-level perceptual decision making (Krishnamurthy et al., 2017, Nassar et al., 2012, Meyniel, 2020, Filipowicz et al., 2020). In the current study, we use a sound location estimation- rather than prediction task to investigate whether the pupil-linked arousal system also reflects implicit low-level weighting of perceptual priors. Participants are asked to localise the last sound in spatially dynamic sequences. Our experimental design features two conditions that are alternated on successive trials: (1) An audio-visual (AV) condition in which we present visual-spatial representations of the sound sources along with each sound except for the last. This condition will participants to maintain a stable spatial mapping between the sound sources of and their abstract visual representations that are required for behavioural responses. It further acts as a close replication of the study by Krishnamurthy et al. (2017). (2) An auditory-only (A) condition, which allows us to test whether spatial priors can be formed for purely auditory stimuli or whether visual representations of their source are required. Moreover, by lack of visual stimulation, the A-only condition is ideally suited to test the hypothesized relationship between the arousal system, assessed through pupillometry, and implicit low-level prior weighting in auditory spatial perception (even during ongoing sound sequence presentation, i.e., not contaminated by response preparation - see Exploratory analysis section)

Confirming pupil dilation as physiological marker of Bayesian inference in dynamic auditory localization

Bayesian theory has been applied successfully to explain human perception in noisy and volatile environments. Previous studies used explicit predictive-inference tasks to show that responses of the pupil-linked arousal system correlate with the weighting of prior knowledge during high-level perceptual decision making (Krishnamurthy et al., 2017, Nassar et al., 2012, Meyniel, 2020, Filipowicz et al., 2020). In the current study, we use a sound location estimation- rather than prediction task to investigate whether the pupil-linked arousal system also reflects implicit low-level weighting of perceptual priors. Participants are asked to localise the last sound in spatially dynamic sequences. Our experimental design features two conditions that are alternated on successive trials: (1) An audio-visual (AV) condition in which we present visual-spatial representations of the sound sources along with each sound except for the last. This condition will participants to maintain a stable spatial mapping between the sound sources of and their abstract visual representations that are required for behavioural responses. It further acts as a close replication of the study by Krishnamurthy et al. (2017). (2) An auditory-only (A) condition, which allows us to test whether spatial priors can be formed for purely auditory stimuli or whether visual representations of their source are required. Moreover, by lack of visual stimulation, the A-only condition is ideally suited to test the hypothesized relationship between the arousal system, assessed through pupillometry, and implicit low-level prior weighting in auditory spatial perception (even during ongoing sound sequence presentation, i.e., not contaminated by response preparation - see Exploratory analysis section)