Improved cardiorespiratory fitness is associated with functional changes in hippocampus during episodic memory pattern completion

Abstract

Background

Aerobic exercise that improves cardiorespiratory fitness (CRF) may induce hippocampal changes that help counteract age-related memory decline. The Umeå HIT Study, a randomized controlled trial, examined three months of controlled high-intensity interval training (HIT) and moderate-intensity training (MIT) in older adults. Here, we tested whether increases in CRF (VO₂peak), regardless of training modality, predicted changes in episodic-memory pattern completion and hippocampal structure and function (CA4/DG, CA2/3, CA1).

Method

Forty-two older adults (66–79 years, 45% males) not engaged in regular physical exercise participated in 3 months of twice-weekly supramaximal HIT (20 min including 10 × 6-s intervals) or aerobic MIT (40 min including 3 × 8-m intervals). Before and after the exercise interventions, the participants underwent magnetic resonance imaging (MRI) of the hippocampus, including an episodic memory pattern completion task with concomitant functional MRI.

Results

Exercise-induced change in VO₂peak (M = 1.5 mL/kg/min, 95% CI[0.8; 2.3]) after three months aerobic exercise of HIT or MIT did not predict change in pattern completion (F_(1,33) = 0.02, B = −0.061 p = .883, r² = 0.001). However, change in VO₂peak predicted BOLD signal change in the left hippocampal subfield CA4/DG (F_(1,33) = 4.56, B = 0.06 p = .04, r² = 0.12), which in turn, predicted change in pattern completion (F_(1,34) = 5.19, B = 0.026, p = .029, r² = 0.13).

Conclusion

Three months of high- or moderate-intensity training which improves CRF may lead to hippocampal functional changes that, in turn, are linked to enhanced episodic memory pattern completion.