Experimental investigation of the effects of acute exercise on memory interference

Behavioural reconsolidation interference not observed in a within-subjects design

Studies of reconsolidation interference posit that reactivation of a previously consolidated memory via a reminder brings it into an active, labile state, leaving it open for potential manipulation. If interfered with, this may disrupt the original memory trace. While evidence for pharmacological reconsolidation interference is widespread, it remains unclear whether behavioural interference using the presentation of competing information can engender it, especially in declarative memory. Almost all previous studies in this area have employed between-subjects designs, in which there are potential confounds, such as different retrieval strategies for the multiple conditions. In the current studies, within-subjects paradigms were applied to test the effects of reconsolidation interference on associative recognition and free recall. In Experiment 1, participants engaged in pair-associate learning of unrelated object pictures on Day 1, and after a reminder, interference, reminder + interference, or no manipulation (control) on Day 2, were tested on associative recognition of these pairs on Day 3. In Experiments 2 and 3, memoranda were short stories studied on Day 1. On Day 2, stories were assigned to either control, reminder, interference by alternative stories, or reminder + interference conditions. On Day 3 participants recalled the Day 1 stories, and answered yes/no recognition questions. Reminders improved subsequent memory, while interference was effective in reducing retrieval in differing degrees across the experiments. Importantly, the reminder + interference condition was no more effective in impairing retrieval than the interference-alone condition, contrary to the prediction of the behavioural reconsolidation-interference approach.

Association of physical activity on memory interference: Boston Puerto Rican Health Study

Background : The objective of this study was to evaluate the association between habitual physical activity engagement on memory interference. The present analysis used cross-sectional data from the Boston Puerto Rican Health Study (n=1,241; mean age= 57.2; 72.1% female).

Methods : Physical activity was evaluated via self-report. Memory interference was evaluated using a word-list paradigm. The memory task included learning a list of 16 words (List A; 5 trials), followed by a distractor list (List B), and then an immediate recall of List A. Proactive interference occurs when preceding stimuli (e.g., Trial 1 and Trial 5 of List A) interferes with performance on a subsequent stimuli (List B). Retroactive interference occurs when subsequent stimuli (List B) interferes with the recall of previously encoded stimuli (Trial 5).

Results : For proactive interference, there was no association between physical activity and the difference between performance on List B and Trial 1 of List A (β=0.00001; P =0.96). Similarly, for retroactive interference, there was no association between physical activity and the difference between the short delay recall and Trial 5 of List A (β=0.0002; P=0.50).

Conclusion : The present study did not observe an association between habitual physical activity on attenuating memory interference.

The Impact of Acute Exercise Timing on Memory Interference

This study evaluated whether the timing of acute exercise can attenuate a memory interference effect. Across two experiments, participants completed an AB/AC memory task. Participants studied eight word pairs; four denoted AB (e.g., Hero - Apple) and four control (DE) pairs. Following this List 1, participants studied eight additional word pairs (List 2); four denoted AC, re-using words from the AB pairs (e.g., Hero - Project) and four control (FG) pairs. Following their study of both lists, participants completed a cued recall assessment. In Experiment 1 (N = 100), an acute exercise bout occurred before the AB/AC memory interference task, and the participants' three lab visits (successive conditions) were control, moderate-intensity (50% HRR; heart rate reserve) exercise, and vigorous-intensity (80% HRR) exercise. In Experiment 2 (N = 68), the acute exercise occurred between List 1 and List 2, and the participants' two lab visits (successive conditions) were a (80% HRR) vigorous-intensity exercise visit and a control visit. Across both experiments, we observed evidence of both proactive and retroactive interference (p < .05), but acute exercise, regardless of intensity, did not attenuate this interference (p > .05). Acute moderate-intensity exercise was better than control or vigorous-intensity exercise in enhancing associative memory (p < .05), independent of interference. In Experiment 2, vigorous intensity exercise was associated with more pronounced interference (p < .05). Our results suggest that acute exercise can enhance associative memory performance, with no attenuation of interference by exercise.

Motor behavior-induced prefrontal cortex activation and episodic memory function

BACKGROUND

The objective of this paper was to evaluate the potential individual and combined effects of acute exercise coupled with bilateral interhemispheric activation on episodic memory function. Six experiments were conducted.

METHODS

Experiment 1 was a within-subject, counterbalanced experiment. Participants completed four visits, including 1) exercise and saccadic eye movements, 2) exercise only, 3) saccadic eye movements only, and 4) no exercise and no saccadic eye movements (control). A word-list memory assessment was employed, including a long-term (20-min delay) memory evaluation. In Experiment 2, we evaluated the effects of saccadic eye movements on prefrontal cortex oxygenation, a proxy for neuronal activity. Similarly, in our third experiment, we evaluated the effects of acute exercise on prefrontal cortex oxygenation. Thus, experiments 2 and 3 were employed to provide mechanistic insights from the results shown in experiment 1. Experiment 4 replicated Experiment 1, but instead of increasing prefrontal cortex activation via saccadic eye movements, we used a fist clenching protocol. Experiment 5 evaluated the effects of fist clenching on prefrontal cortex oxygenation.

RESULTS

Collectively, these 5 experimental studies showed that acute exercise (Experiment 1), saccadic eye movements (Experiment 1), and fist clenching (Experiment 4) enhanced memory function, and that acute exercise (Experiment 3), saccadic eye movements (Experiment 2) and fist clenching (Experiment 5) all increased prefrontal cortex oxygenation. Experiment 6 demonstrated that prefrontal cortex oxygenation was positively associated with episodic memory function.

CONCLUSION

These six experiments suggest that several behaviors, such as acute exercise, saccadic eye movements and fist clenching may improve memory function and may, potentially, do so via increases in prefrontal cortex oxygenation.

Effects of exercise on proactive interference in memory: potential neuroplasticity and neurochemical mechanisms

Proactive interference occurs when consolidated memory traces inhibit new learning. This kind of interference decreases the efficiency of new learning and also causes memory errors. Exercise has been shown to facilitate some types of cognitive function; however, whether exercise reduces proactive interference to enhance learning efficiency is not well understood. Thus, this review discusses the effects of exercise on proactive memory interference and explores potential mechanisms, such as neurogenesis and neurochemical changes, mediating any effect.

Hypothesized Mechanisms Through Which Exercise May Attenuate Memory Interference

In this paper we introduce a mechanistic model through which exercise may enhance episodic memory, specifically via attenuating proactive and retroactive memory interference. We discuss the various types of memory, different stages of memory function, review the mechanisms behind forgetting, and the mechanistic role of exercise in facilitating pattern separation (to attenuate memory interference).

Effects of Exercise on Memory Interference in Neuropsychiatric Disorders

There are several mechanisms that cause memory impairment, including motivated forgetting, active forgetting, natural decay, and memory interference. Interference occurs when one is attempting to recall something specific, but there is conflicting information making it more difficult to recall the target stimuli. In laboratory settings, it is common to measure memory interference with paired associate tasks-usually utilizing the AB-CD, AB-AC, AB-ABr, or AB-DE AC-FG method. Memory impairments are frequent among those with neuropsychiatric disorders such as depression, schizophrenia, and multiple sclerosis. The memory effects of each condition differ, but are all related to alterations in brain physiology and general memory deterioration. Exercise, or physical activity, has been demonstrated to attenuate memory interference in some cases, but the mechanisms are still being determined. Further research is needed on memory interference, in regard to exercise and neuropsychiatric disorders.

Effects of Exercise on Long-Term Potentiation in Neuropsychiatric Disorders

Various neuropsychiatric conditions, such as depression, Alzheimer's disease, and Parkinson's disease, demonstrate evidence of impaired long-term potentiation, a cellular correlate of episodic memory function. This chapter discusses the mechanistic effects of these neuropsychiatric conditions on long-term potentiation and how exercise may help to attenuate these detrimental effects.

The Effects of Acute Exercise on Retroactive Memory Interference

PURPOSE

Retroactive interference involves the disruption of previously encoded information from newly learned information and thus may impair the consolidation of long-term memory. The objective of this study was to evaluate whether acute exercise can attenuate retroactive memory interference.

DESIGN

Three experimental studies were employed. Experiment 1 employed a between-subject randomized control trial (RCT) involving moderate-intensity walking (15 minutes). Experiment 2 employed a between-subject RCT involving high-intensity jogging (15 minutes). Experiment 3 employed a within-subject RCT involving moderate-intensity walking (15 minutes).

SETTING

University setting.

PARTICIPANTS

One hundred twelve young adults.

MEASURES

After exercise, memory interference was evaluated from an episodic word-list memory task, involving the recall of 2 word lists.

RESULTS

The pooled effect size (standard difference in means: -0.35; 95% confidence interval: -0.64 to -0.06) across the 3 experiments was statistically significant (P = .01).

CONCLUSION

We provide suggestive evidence that acute, short-duration exercise may help attenuate a retroactive memory interference effect. Implications of these findings for exercise to improve memory and attenuate memory decay are discussed.

Experimental Effects of Acute Exercise in Attenuating Memory Interference: Considerations by Biological Sex

Background and Objectives: The objective of this experiment was to evaluate the effects of acute exercise on memory interference and determine if this potential relationship is moderated by sex. Materials and Methods: A randomized controlled experiment was conducted (N = 40), involving young adult males (n = 20) and females (n = 20) completing two counterbalanced visits (exercise and no exercise). The exercise visit involved an acute (15 min), moderate-intensity bout of treadmill exercise, while the control visit involved a time-matched seated task. Memory interference, including both proactive interference and retroactive interference, involved the completion of a multi-trial memory task. Results: In a factorial ANOVA with the outcome being List B, there was a main effect for condition (F(1,38) = 5.75, P = 0.02, n²_p = 0.13), but there was no main effect for sex (F(1,38) = 1.39, P = 0.24, n²_p = 0.04) or sex by condition interaction (F(1,38) = 1.44, P = 0.23, n²_p = 0.04). Conclusion: In conclusion, acute moderate-intensity exercise was effective in attenuating a proactive memory interference effect. This effect was not moderated by biological sex.

Experimental Manipulation of Psychological Control Scenarios: Implications for Exercise and Memory Research

The purpose of this experiment was to evaluate the extent to which variations in control activities influence memory function, as well as to investigate the participants’ memory expectations for the various conditions. A within-subject, counterbalanced experimental design was employed. Across four visits, participants engaged in four tasks, including an acute exercise session, and three cognitive-engagement control tasks of varying degrees of cognitive engagement and valence, namely reading neutral text, looking at a video, and puzzle completion. Participants’ perceived expectations for how each condition would improve their memory performance was also assessed. We observed no differences in objective cognitive performance or outcome expectations across the three evaluated control tasks, and thus, future studies may wish to employ either of these control tasks, which should not compromise making comparisons across studies.

The effects of acute exercise on episodic memory function among young university students: moderation considerations by biological sex

Background: The objective of this study was to evaluate potential sex-specific differences on episodic memory function and determine whether sex moderates the effects of acute exercise on episodic memory.

Methods: A randomized controlled intervention was employed. This experiment was conducted among young University students (mean age = 21 years). Both males (n=20) and females (n=20)completed two counterbalanced laboratory visits, with one visit involving a 15-minute bout of moderate-intensity exercise prior to the memory task. The control visit engaged in a time matched seated task. Memory function (including short-term memory, learning, and long-term memory) was assessed from the RAVLT (Rey Auditory Verbal Learning Test).

Results: We observed a significant main effect for time (P<0.001, ƞ²_p= 0.77) and a marginally significant main effect for sex (P=0.06, ƞ²_p= 0.09), but no time by sex by condition interaction(P=0.91, ƞ²_p= 0.01). We also observed some suggestive evidence of a more beneficial effect of acute exercise on memory for females.

Conclusion: In conclusion, females outperformed males in verbal memory function. Additional research is needed to further evaluate whether sex moderates the effects of acute exercise on memory function.

Effects of Intensity-Specific Acute Exercise on Paired-Associative Memory and Memory Interference

The improvement of memory performance is an ever-growing interest in research, with implications in many fields. Thus, identifying strategies to enhance memory and attenuate memory interference is of great public health and personal interest. The objective of this paper was to evaluate the role of intensity-specific acute exercise on improving paired-associative memory function and attenuating memory interference. A counterbalanced, randomized controlled, within-subject experimental design was employed. The three counterbalanced visits included a control visit, moderate-intensity exercise (50% of HRR; heart rate reserve) and vigorous-intensity exercise (80% of HRR), all of which occurred prior to the memory assessment. To evaluate memory interference, an AB/AC paired-associative task was implemented for each laboratory visit. The number of correctly recalled words from List 1 (AB–DE) was statistically significantly (F = 4.63, p = 0.01, η2p = 0.205) higher for the vigorous-intensity condition (M = 6.53, SD = 1.54) as compared to moderate-intensity (M = 6.11, SD = 1.59) and control (M = 5.00, SD = 2.56) conditions. No statistical significance was found between proactive interference or retroactive interference across the experimental conditions. This experiment provides evidence for an intensity-specific effect of acute exercise on short-term, paired-associative memory, but not memory interference.

An integrated model of acute exercise on memory function

Memory is a complex cognition that plays a critical role in daily functioning. This review discusses the dynamic effects of acute exercise on memory function, via a hypothesized exercise-memory interaction model, taking into consideration multiple memory systems and exercise parameters.

Association between habitual physical activity on episodic memory strategy use and memory controllability

Background: The primary objective of this study was to evaluate the association between habitual physical activity engagement and perceived controllability of memory function. Secondary objectives included the evaluation of physical activity on memory strategy use, and whether the latter mediates the relationship between physical activity on memory controllability. Methods: Two-hundred and nine young adults (M_age=25 y) completed a brief survey evaluating physical activity (Physical Activity Vital Signs Questionnaire), memory strategy use (Memory Functioning Questionnaire), and memory controllability (Memory Controllability Inventory). Results: Physical activity was not associated with memory strategy use (β=0.68; 95% CI: -1.25,2.62; P=0.48), nor was memory strategy use associated with memory controllability. Physical activity was consistently associated with various attributes of memory controllability, including Present Ability (β=1.10; 95% CI: 0.07, 2.12; P=0.03), Potential Improvement (β=0.84; 95% CI:0.05, 1.63; P=0.03), Effort Utility (β=0.87; 95% CI: 0.11, 1.61; P=0.02), Inevitable Decrement (β=-1.19; 95% CI: -2.19, -0.19; P=0.02) and Alzheimer's likelihood (β=-1.21; 95% CI: -2.29,-0.12; P=0.02). Conclusion: Physical activity is consistently associated with greater perceptions of memory controllability. Future longitudinal and experimental work on this topic is warranted to evaluate if physical activity can foster an individual's ability to modify their behavior and cognitions to enhance and preserve memory function.