Exercise and Emotional Memory: a Systematic Review

The Effect of Exercise Intensity on Affective and Repetition Priming in Middle-Aged Adults

Previous research has shown that physical exercise improves memory. In the present study, we investigated the possible effects of the intensity of physical exercise as a function of the affective valence of words on implicit memory. In the study, 79 young adult volunteers were randomly assigned to perform moderate- (50% VO2max) or high-intensity exercise (80% VO2max) on a stationary bike. Once the required exercise intensity was achieved, participants performed an affective and repetition priming task concurrently with the physical exercise. Both groups showed similar repetition priming. The moderate-intensity exercise group showed affective priming with positive words, while affective priming was not found in the high-intensity exercise group. Facilitation occurred in both groups when a negative target word was preceded by a positive prime word. Our results suggest that the positive effect of physical exercise on memory is modulated by the affective valence of the stimuli. It seems that moderate-intensity exercise is more beneficial for implicit memory than high-intensity exercise.

Effects of acute exercise on emotional memory

Research has demonstrated beneficial effects of acute exercise on memory for neutral materials, such as word lists of neutral valence/low arousal. However, the impacts of exercise on emotional memory is less understood. Across three laboratory experiments in college students, we tested if acute exercise could enhance both neutral and emotional memory performance, anticipating a greater effect for emotional memory. We examined effects of exercise at varying intensities (Experiment 1: high-intensity; Experiment 2: low- and high-intensity; Experiment 3: moderate-intensity), of diverse modalities (Experiment 1: treadmill jogging; Experiment 2: cycling; Experiment 3: open-skill (racquetball) and closed-skill (treadmill jogging) exercise), and on emotional memory performance assessed at increasing levels of hippocampal dependency (Experiment 1: Y/N recognition task; Experiment 2: paired-associative recognition task; Experiment 3: cued-recall task). We found that, in all experiments, acute exercise did not significantly influence emotional or neutral memory performance relative to sedentary control conditions. However, we observed several noteworthy outcomes indicating that acute exercise may be linked to improvements in memory confidence and accuracy for central aspects of emotional memory stimuli, and that select exercise modalities (e.g. treadmill exercise) may also be associated with increased frequency of memory intrusions.

Enhanced recognition of emotional images is not affected by post-exposure exercise-induced arousal

Research suggests that aerobic exercise (i.e., exercise aiming to improve cardiovascular fitness) promotes cognition, but the impact on memory specifically, is unclear. There is some evidence to suggest that as little as one session of post-learning exercise benefits memory consolidation. Furthermore, memory may be particularly facilitated by exercise when the individual is emotionally aroused while encoding stimuli. The current study tested whether exercise after exposure to neutral and emotional images improved memory consolidation of the items among university students. Ninety-nine students were randomly instructed to either exercise or not exercise after viewing a set of images that were positive, neutral, and negative in valence, and they were later tested on their memory. Although emotional images were remembered better than non-emotional images, the results suggested that exercise did not influence this effect or enhance consolidation of the items overall. Explanations and implications for these findings are discussed.

Acute and Chronic Exercise Effects on Human Memory: What We Know and Where to Go from Here

Although the acquisition, storage, and retrieval of memories was once thought to happen within a single memory system with multiple processes operating on it, it is now believed that memory is comprised of both distinct and interacting brain systems [...].

Acute physical exercise promotes the consolidation of emotional material

Physical exercise can improve cognitive functions and promote learning and memory, especially when performed in close temporal proximity to the encoding of information. This benefit may occur due to circulating stress hormones released in response to acute exercise. When administered after encoding, acute stress typically enhances the consolidation of emotional stimuli. However, whether acute exercise also selectively modulates emotional memories remains to be explored. Likewise, the potential role of sex in moderating these effects has not been addressed so far. Here, we tested whether a single bout of aerobic exercise after learning boosts the consolidation and thus long-term memory for emotional versus neutral visuospatial stimuli. Healthy men and women learned an object-location task and subsequently were exposed to a vigorous-treadmill running task or control intervention. Memory was assessed 24 h later. Acute exercise significantly increased heart rate and salivary cortisol in both sexes and selectively facilitated the consolidation of emotional stimuli. In particular, we found improved memory for negative items in women and better recall of positive items in men following exercise exposure. This memory benefit was positively related to the increase in heart rate and cortisol in both men and women, suggesting that the favorable effects of acute exercise on emotional memory may be mediated via a co-activation of the sympathetic nervous system and the hypothalamus-pituitary-adrenocortical axis. Our findings thereby provide first evidence for the improvement of emotional memory consolidation by acute physical exercise that appears to rely on similar neuroendocrine mechanisms as psychosocial stressors. Given that exercise is healthy, cost-effective and practical in nature, it constitutes an ideal behavioral intervention strategy for boosting memory in clinical and educational settings alike.

The effects of sedentary behavior on memory and markers of memory function: a systematic review

Objective: To evaluate the association of sedentary behavior on memory and markers of memory among humans of all ages.Methods: PubMed, PsychInfo, Sports Discus and Google Scholar databases were searched. Inclusionary criteria included: Published in English; conducted among humans (children to older adults); employ a cross-sectional, prospective or experimental design; include a measure of sedentary behavior as the independent variable (e.g. time spent sitting or watching television); and include a memory-related outcome measure (e.g. behavioral performance on a memory task, brain tissue volume in a memory structure). Information on participant characteristics, study design, sedentary behavior measure, memory outcome measure, and hypothesized mechanisms were extracted. The relationship between sedentary behavior and memory was synthesized while considering the data extraction parameters.Results: In total, 25 articles met the inclusionary criteria, including 8 studies among children/adolescents and 17 among adults. Sedentary behavior was assessed subjectively (e.g. TV viewing, computer use, reading) and objectively (e.g. accelerometry). Outcome measures included behavioral performance on various memory tasks (e.g. episodic and working memory), BDNF levels, brain volumetric measures of the temporal lobe, and hippocampal glucose metabolism. Overall, for both the child and adult studies, findings were mixed, with studies demonstrating null, inverse, and positive associations between sedentary behavior and memory. Sedentary behavior type may play a distinct role in the relationship between sedentary behavior and memory, as computer use, in particular, appeared to favorably influence memory when compared to other sedentary types (e.g. TV viewing, which showed in inverse association with memory in select studies).Conclusion: There is conflicting evidence of the relationship between sedentary behavior and memory-related outcomes among children and adults. Future studies are needed to further disentangle these complex interrelationships. Such studies should also carefully consider how physical activity may or may not moderate these relationships.

Acute Exercise on Memory Reconsolidation

Background and Objective: Once a memory is reactivated, it enters a labile state and, thus, is vulnerable to memory decay and/or distortion. Recent research demonstrates that acute, high-intensity exercise is associated with enhanced episodic memory function. Very limited research, however, has evaluated whether acute exercise can attenuate memory distortion from memory reactivation, which was the purpose of this study. Methods: A between-subject randomized controlled intervention was employed. Participants (N = 80) were randomly assigned to one of four groups, including (1) reminder with exercise, (2) reminder, (3) no reminder, and (4) interference control. For the groups, participants completed three visits (Visit 1, 2, and 3), which all occurred 48 hours apart. An exception to this was the interference control group, which did not complete Visit 2. On Visit 2, the reminder with exercise group engaged in a 15 min bout of high-intensity exercise (80% of heart rate reserve) immediately after memory reactivation. On Visit 3, participants engaged in a free recall (4 trials) of the memory task encoded on Visit 1. Results: In a 4 (groups) × 4 (learning trials) mixed-measures ANOVA, with the group as the between-subjects variable and the learning trials (1–4) as the within-subject variable, there was a significant main effect group, F(3, 76) = 4.18, p = 0.008, η²_p = 0.14, and a significant main effect for the learning trials, F(2.40, 182.59) = 49.25, p < 0.001, η²_p = 0.39, but there was no group by learning trials interaction, F(7.20, 182.59) = 1.07, p = 0.38, η²_p = 0.04. Conclusion: Our findings suggest that exercise may, potentially, attenuate memory distortion from memory reactivation. However, future work is needed to confirm these findings before any strong conclusions can be reached.

The Endocannabinoid System as a Potential Mechanism through which Exercise Influences Episodic Memory Function

Emerging research demonstrates that exercise, including both acute and chronic exercise, may influence episodic memory function. To date, mechanistic explanations of this effect are often attributed to alterations in long-term potentiation, neurotrophic production, angiogenesis, and neurogenesis. Herein, we discuss a complementary mechanistic model, suggesting that the endocannabinoid system may, in part, influence the effects of exercise on memory function. We discuss the role of the endocannabinoid system on memory function as well as the effects of exercise on endocannabinoid alterations. This is an exciting line of inquiry that should help delineate new insights into the mechanistic role of exercise on memory function.

Protective and therapeutic effects of exercise on stress-induced memory impairment

The objective of this paper was to systematically evaluate the potential preventive and therapeutic effects of exercise in attenuating stress-induced memory impairment. A systematic review was employed, searching PubMed, PsychInfo, Sports Discus and Google Scholar databases. For eligibility, studies had to be published in English, employ an experimental design, have the acute or chronic bout of exercise occur prior to, during or after the stressor, implement a psychophysiological stressor, and have an assessment of memory function occurring after the stressor. In total, 23 studies were evaluated, all of which were conducted among animal models. All 23 studies employed a chronic exercise protocol and a chronic stress protocol. Eight studies evaluated a preventive model, three employed a concurrent model, ten studies employed a therapeutic model, and two studies evaluated both a preventive and therapeutic model within the same study. Among the eight studies employing a preventive model, all eight demonstrated that the stress regimen impaired memory function. In all eight of these studies, when exercise occurred prior to the stressor, exercise attenuated the stress-induced memory impairment effect. Among the ten studies employing a therapeutic model, one study showed that the stress protocol enhanced memory function, one showed that the stress protocol did not influence memory, and eight demonstrated that the stress regimen impaired memory function. Among the eight studies showing that the stress protocol impaired memory function, all eight studies demonstrated that exercise, after the stressor, attenuated stress-induced memory impairment. Within animal models, chronic stress is associated with memory impairment and chronic exercise has both a preventive and therapeutic effect in attenuating stress-induced memory impairment. Additional experimental work in human studies is needed. Such work should also examine acute exercise and stress protocols.

The Experimental Effects of Acute Exercise on Long-Term Emotional Memory

Emerging work suggests that acute, moderate-intensity aerobic exercise may help to subserve episodic memory of neutral stimuli. Less investigated, however, is whether acute exercise is associated with enhanced memory recognition of emotional stimuli, which was the purpose of this experiment. A parallel-group randomized controlled experiment was employed. Participants (mean age = 20 yr) were randomized into an exercise (n = 17) or control group (n = 17). The exercise group engaged in a 15-min bout of moderate-intensity treadmill walking. Emotional memory recognition was assessed via images from the International Affective Picture System, including assessments of varying degrees of valence and arousal. Memory recognition was assessed at 1 day, 7 days, and 14 days post-memory encoding. We observed a significant main effect for time (F(2) = 104.2, p < 0.001, η²_p = 0.77) and a significant main effect for valence–arousal classification (F(4) = 21.39, p < 0.001, η²_p = 0.40), but there was no significant time by group interaction (F(2) = 1.09, p = 0.34, η²_p = 0.03), classification by group interaction (F(4) = 0.12, p = 0.97, η²_p = 0.01), time by classification interaction (F(8) = 1.78, p = 0.08, η²_p = 0.05), or time by classification by group interaction (F(8) = 0.78, p = 0.62, η²_p = 0.02). In conclusion, emotional memory recognition decreased over the 14-day follow-up period and this rate of memory decay was not altered by acute moderate-intensity exercise engagement. We discuss these findings in the context of exercise intensity and the temporal effects of exercise.