Sympathetic arousal increases a negative memory bias in young women with low sex hormone levels

Abstract

Emotionally arousing events are typically better attended to and remembered than neutral ones. Current theories propose that arousal-induced increases in norepinephrine during encoding bias attention and memory in favor of affectively salient stimuli. Here, we tested this hypothesis by manipulating levels of physiological arousal prior to encoding and examining how it influenced memory for emotionally salient images, particularly those that are negative rather than positive in valence. We also tested whether sex steroid hormones interact with noradrenergic activity to influence these emotional memory biases in women. Healthy naturally cycling women and women on hormonal contraception completed one of the following physiological arousal manipulations prior to viewing a series of negative, positive and neutral images: 1) Immediate handgrip arousal – isometric handgrip immediately prior to encoding, 2) Residual handgrip arousal – isometric handgrip 15 min prior to encoding, or 3) No handgrip. Sympathetic arousal was measured throughout the session via pupil diameter changes. Levels of 17β-estradiol and progesterone were measured via salivary samples. Memory performance was assessed approximately 10 minutes after encoding using a surprise free recall test. The results indicated that handgrip successfully increased sympathetic arousal compared to the control task. Under immediate handgrip arousal, women showed enhanced memory for negative images over positive images; this pattern was not observed in women assigned to the residual and no-handgrip arousal conditions. Additionally, under immediate handgrip arousal, both high estradiol and progesterone levels attenuated the memory bias for negative over positive images. Follow-up hierarchical linear models revealed consistent effects when accounting for trial-by-trial variability in normative International Affective Picture System valence and arousal ratings. These findings suggest that heightened sympathetic arousal interacts with estradiol and progesterone levels during encoding to increase the mnemonic advantage of negative over positive emotional material.

Noradrenergic mechanisms of arousal’s bidirectional effects on episodic memory

“…Previous work shows that women exhibit significantly larger amnestic effects of emotional oddballs on preceding neutral stimuli (Strange et al, 2003). We also did not control for menstrual cycle phase or birth control use, which have been shown to alter emotional memory enhancements induced by elevated noradrenergic activity (Nielsen et al, 2015). Moreover, future pharmacological studies using propranolol should account for participants’ body mass index (BMI) based on evidence of interactions between drug dose size and body mass (Sokol-Hessner et al, 2015).…”

The Locus Coeruleus: Essential for Maintaining Cognitive Function and the Aging Brain

“…NE inhibits pupil constriction [115, 116] and pupils dilate more when NE levels increase, such as during aerobic exercise [118], muscular exertion [119, 120], viewing emotionally or sexually arousing pictures [121], or wakefulness compared with sleep [122, 123]. In monkeys, LC stimulation prompts pupil dilation [117], and in humans, pupil dilation correlates with LC activity seen using functional neuroimaging [124].…”

Arousal amplifies biased competition between high and low priority memories more in women than in men: The role of elevated noradrenergic activity

“…Akin to genotyping studies, a recent study showed that isometric handgrip-induced increases in NE bias memory towards highly arousing negative information, suggesting that incidentally elevating noradrenergic activity selectively amplifies the effects of phasic arousal on memory (Nielsen et al, 2015). Critically, our results suggest that greater background NE levels were also associated with competitive tradeoffs in memory consolidation: women with greater noradrenergic activity showed greater arousal-biased competition memory outcomes at the trial level.…”

“…For instance, GANE aligns with models positing that NE biases attention (Markovic et al, 2014) and memory consolidation (McGaugh & Roozendaal, 2002; McGaugh, 2013) to favor emotional or affectively salient information over neutral information (Markovic et al, 2014). More recently, it was demonstrated that increasing NE levels with isometric handgrip in young women enhances selective memory for negative emotional stimuli (Nielsen et al, 2015), suggesting that NE release enhances memory selectivity even when sympathetic arousal is manipulated externally. Thus, the dominance of emotional stimuli in perception and memory may be due both to the prioritization they acquire through their motivational relevance (e.g., reward or punishment) as well as the presence of elevated NE.…”

“…However, there is also evidence of contradictory mnemonic effects of sex steroid hormones under arousal. For example, Nielsen et al (2015) found that the memory-biasing effects of handgrip-induced increases in NE only occurred in women with lower estradiol and progesterone levels at encoding. Wegerer et al (2014) also revealed that low levels of estradiol are associated with stronger intrusive memories for emotional materials (Wegerer et al, 2014).…”