Effects of acute aerobic exercise on mnemonic discrimination performance in older adults

Abstract

Objectives: Ample evidence suggests exercise is beneficial for hippocampal function. Furthermore, a single session of aerobic exercise provides immediate benefits to mnemonic discrimination performance, a highly hippocampal-specific memory process, in healthy younger adults. However, it is unknown if a single session of aerobic exercise alters mnemonic discrimination in older adults, who generally exhibit greater hippocampal deterioration and deficits in mnemonic discrimination performance. Methods: We conducted a within subject acute exercise study in 30 cognitively healthy and physically active older adults who underwent baseline testing and then completed two experimental visits in which they performed a mnemonic discrimination task before and after either 30 min of cycling exercise or 30 min of seated rest. Linear mixed-effects analyses were conducted in which condition order and age were controlled, time (pre vs. post) and condition (exercise vs. rest) were modeled as fixed effects, and subject as a random effect. Results: No significant time by condition interaction effect was found for object recognition (p = .254, η2=.01), while a significant reduction in interference was found for mnemonic discrimination performance following the exercise condition (p = .012, η2=.07). A post-intervention only analysis indicated that there was no difference between condition for object recognition (p = .186, η2=.06), but that participants had better mnemonic discrimination performance (p < .001, η2=.22) following the exercise. Conclusions: Our results suggest a single session of moderate-intensity aerobic exercise may reduce interference and elicit better mnemonic discrimination performance in healthy older adults, suggesting benefits for hippocampal-specific memory function.

Acute cycling exercise and hippocampal subfield function and microstructure in healthy older adults

“…For example, Suwabe et al (2017), (2018) report that 10 min of light and moderate‐intensity aerobic exercise in college‐aged adults was associated with better MD on highly similar lures. We have recently reported that moderate‐intensity exercise in active older adults was associated with reduced MD interference seen from pre to post‐seated rest; however, MD did not specifically improve from pre to post‐exercise (Callow, Pena, et al, 2022a). While our current finding of reduced MD performance was not in the direction we hypothesized or reported in Suwabe et al (2017), (2018), there are several reasons why a longer bout of acute moderate to vigorous intensity exercise in healthy older adults may have led to lower MD performance.…”

“…Notably, the effect of acute exercise on hippocampal memory depends on the timing, length, and intensity of the exercise bout and the cognitive task tested (Chang et al, 2012; Loprinzi et al, 2021; Marchant et al, 2020; Sng et al, 2018). Although moderate to vigorous intensity acute aerobic exercise has generally been shown to provide benefits for cognition and executive function in older adults (Chang et al, 2012; Moreau & Chou, 2019), the effects of acute exercise for hippocampal‐specific MD and general memory function are far less established (Callow, Pena, et al, 2022a; Etnier et al, 2021; Griebler et al, 2022). In fact, several studies suggest that higher‐intensity exercise may be stressful, elevating cortisol and lactate levels and specifically interfering with hippocampal‐dependent memory (Basso et al, 2015; Marchant et al, 2020; Soya et al, 2007).…”

“…and one more (female) was excluded due to failure to use the "similar" response button at least 10 times. This criteria has been similarly employed to remove participants who failed to follow task instructions (Callow, Pena, et al, 2022). An additional three subjects (females) were excluded due to MRI goggles that fogged and prevented completion of the fMRI task at one of the two time points.…”

“…Growing evidence indicates acute aerobic exercise can alter hippocampal integrity, function, and memory performance (Callow, Pena, et al, 2022a; Callow, Won, Alfini, et al, 2021; El‐Sayes et al, 2019; Loprinzi et al, 2021). However, these effects may depend on the duration, timing, and intensity of the exercise, the age of the participants, and the specific memory construct tested (Loprinzi et al, 2021).…”

“…For example, a short bout of light to moderate‐intensity aerobic exercise can lead to better mnemonic discrimination (MD) on highly similar stimuli in college‐aged younger adults (Suwabe et al, 2017, 2018). Meanwhile 20 min of moderate‐intensity exercise can preserve pre to post MD performance in healthy older adults compared to seated rest (Callow, Pena, et al, 2022a). MD is a memory construct that engages the dentate gyrus (DG) and CA3 subfields of the hippocampus by placing a high demand on pattern separation (Stark et al, 2019; Yassa & Stark, 2011) and represents a process by which individuals accurately discern between previously viewed (old) stimuli and newly presented but visually similar (lure) stimuli.…”