It’s well accepted that exercise can positively impact physical health; now, research is starting to examine other benefits of exercise, such as its effect on cognition. Recent research shows that aerobic and cardiovascular exercise can strengthen cognition, specifically impacting the frontal brain regions in charge of executive function (Roig, Nordbrandt, Geertsen, & Nielson, 2013).
Arousal from acute exercise can assist the brain in properly distributing its resources to enhance memory consolidation, neurogenesis, brain plasticity, processing speed, and more (Roig, Skriver, Lundbye-Jensen, Kiens, & Nielsen, 2012; Potter & Keeling, 2005; Sproule, Turner, & Hale, 2011). These mental resources that nurture memory enhancement have widespread benefits., specifically in places that focus on learning and memory such as in schools or when recovering from a stroke (Most, Kennedy, & Petras, 2017).
Exercise is structured bodily exertion aimed at preserving physical fitness or enhancing skeletal muscles. Exercise benefits both cognition and brain health. Aerobic exercise is used to lessen the cognitive decline that comes with old age, including slowing the path of diseases that impact memory, such as Alzheimer’s (Berchtold, Castello, & Cotman, 2010). In addition to slowing the effect of neurological conditions, aerobic exercise promotes cerebral blood flow, brain connectivity, and brain activation (Roig et al., 2012).
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Cardiovascular exercise is often studied as acute or long-term. Meta-analyses show a small to moderate effect of acute exercise on memory performance (Roig et al., 2013; McMorris et al., 2011). Acute exercise occurs as one short period of exercise, contrasting with long-term exercise, which occurs as many periods of exercise done over an extended course of time. Compared to long-term exercise, acute exercise has a stronger effect on memory consolidation and processing because it initiates molecular changes that assist in preparing the optimization of cognitive functions. Researchers explain this psychologically through the impact of arousal on cognition and memory formation and biologically through the increase of catecholamines (Roig et al., 2013).
Biologically, exercise is comparable to stressors because they cause similar bodily arousal. When stressed, the thalamus triggers a response in the hypothalamus via an autonomic nervous system feedback loop and releases catecholamines. These catecholamines include dopamine, norepinephrine, and epinephrine, which are neurotransmitters that are synthesized and then supply noradrenergic an dopaminergic pathways involved in activating brain regions that control executive functions (McMorris et al., 2011).
Acute intense exercise can have a strong effect on the speed of recall and is hypothesized to be due to the increase of catecholamines that escalate processing; however, fewer studies have been able to conclude the impact of exercise on memory accuracy (McMorris et al., 2011). During exercise and arousal, the body releases these catecholamines centrally and peripherally, including those believed to be involved in memory consolidation such as dopamine, norepinephrine, and epinephrine (McMorris et al., 2011; Roig et al., 2013).
In addition to catecholamines, studies have found that exercise and arousal increase brain-derived neurotrophic factor (BDNF) protein levels. BDNF proteins are important for creating and storing memories, so it serves an important role in memory consolidation and hippocampal long-term potentiation and plasticity (Roig et al., 2012). After exercising, BDNF levels remain elevated, and those higher levels of BDNF proteins have correlated with enhanced neural plasticity, potentially serving as an intermediary for physical exercise and learning (Winter et al., 2007).
When the BDNF receptor, tyrosine kinase b (TrkB), is blocked, synaptic protein formation weakens. Based on that, researchers believe that BDNF may induce a signaling cascade impacting cognitive (Berchtold et al, 2010). In a study where participants engaged in acute exercise before performing a vocabulary memory task, the participants showed an increase in peripheral catecholamines and had a 20% increase in vocabulary recall, thus, exhibiting an increase in learning ability. They additionally found a positive correlation between BDNF levels and short-term memory performance after exercising (Winter et al., 2007).
Assessment of memory performance depends on which type of memory is being tested: short-term memory or long-term memory. Memory is the process of cognitively manipulating information for later reproduction. Short-term memory is the mental storage of information for a small amount of time in order to engage in cognitive tasks. Long-term memory is the mental storage of information for a lengthy amount of time based on previous experiences (Cowan, 2008). Short- and long-term memory differ in the memory decay over time and the storage capacity of memories.
Memory recall depends on the time between the exercise and acquiring the information. When performing memory recall tasks, mental rehearsal can be used to keep items in short-term memory. To prevent recall simply due to rehearsal, researchers add in distractions to take the attention away from the items the participants are asked to recall (Cowan, 2008).
When performing recall tasks, the time between acute exercise and the memory task performed in an experiment has a significant effect on the results, including whether the participant exercises before, during, or after the memory task (Roig et al., 2012). If the test is performed during or directly after exercise, the participant may not perform as well due to the change in arousal and mental and physical fatigue. This effect could additionally increase if the exercise is high intensity or has a long duration.
Also, if the test is performed too quickly, the memories may not have as large effects because they did not get to undergo enough consolidation and maturation. So, retention that gives enough time for consolidation improves recall (Roig et al., 2013). People also perform differently throughout the day due to fatigue, and the prime time of day depends on what exact task is being performed (Potter & Keeling, 2005). While there are many time-dependent factors, overall research shows a moderate effect of acute exercise on memory performance (Roig et al., 2013).
Meta-analyses report a moderate effect (Roig et al., 2013; McMorris et al., 2011), but there remain parts of the literature need further exploration and explanation. Studies’ results differ in the strength that exercise improves the acquisition and recollection of memory. This difference is likely due to variation in methods and measures, such as the intensity and kind of exercise, memory tasks performed, and duration between exercise and performance (Berchtold et al., 2010).
Changes in exercise alter which molecular mechanisms are initiated, and thus have different impacts on memory. The literature also has yet to determine the prime duration of exercise and there are mixed results as to if exercise has a greater effect before, during, or after the physical activity. The literature needs more human studies in order to draw stronger and more confident effects of exercise and memory (Roig et al., 2013).
In this study, we will investigate how exercise affects short term memory recall. We predict that if someone exercises before a memory task, then recall will improve. We will measure the relationship between exercise and memory based on the number of words a participant can accurately recall from a word list. By studying ways to improve memory, hopefully we can advance the ways we learn more efficiently, especially in conditions where learning is the main focus, such as in schools and rehabilitation.
