College of Health
32 Effects of Exercise on GABA Levels in the Aging Brain
Ryder Robins; Bradley King; Genevieve Albouy; Abigail White; Anke Van Roy; and Adriana Coletta
Faculty Mentor: Bradley King (Health and Kinesiology, University of Utah)
Background
Aging is associated with substantial declines in cognitive and motor functioning1,2. These declines may be attributed, in part, to age-related decreases in the levels of gamma-aminobutyric acid (GABA) – the brain’s primary inhibitory neurotransmitter – in task relevant brain regions3. GABA plays an important role in the excitation/inhibition balance essential for optimal brain functioning, and as a result, age-associated decreases in GABA have been linked to known decrements in cognition, motor learning, and sensory processing. As exercise has shown promise to mitigate such aging-related decrements4,5,6, one candidate mechanism suggests that it does so by increasing brain GABA levels7,8,9. In this proof-of-concept study, we aim to investigate the extent to which an acute bout of high intensity aerobic exercise can modulate brain GABA levels in healthy older adults. We use magnetic resonance spectroscopy (MRS) to quantify GABA in the primary motor cortex (M1) and the hippocampus (HC) – two brain regions selected for their roles in motor and cognitive functioning, respectively. We hypothesize that high intensity aerobic exercise, as compared to a control (rest) intervention, will increase regional GABA concentrations in older adults, mitigating known age-related decreases in brain GABA levels3.
Methods
The preliminary sample consisted of four apparently healthy, right-handed males between 72-74 years old. Exclusion criteria included known neurological, psychological, and psychiatric conditions as well as contraindications to MRI or high intensity exercise. Participants underwent three sessions over a period of approximately three weeks (Figure 1). The first session consisted of a 6-minute walk test to estimate VO2max10 and measurements of height, weight, resting heart rate (HR), and blood pressure (see Table 1 for participant characteristics). In the second and third sessions, participants completed an exercise or control intervention (order counterbalanced across participants). The exercise intervention consisted of a high-intensity interval training (HIIT) regimen in which periods of high intensity exercise (85-95% of peak heart rate) were alternated with periods of active recovery (50-75% of peak heart rate). For the control intervention, participants sat quietly for a duration equivalent to the HIIT. To measure GABA levels, a 3T Siemens scanner was used to perform GABA-edited MRS immediately pre and post each intervention. A high-resolution T1 structural image at the beginning of each scan was referenced to place voxels over the left M1 (3 x 3 x 3cm3) and the left HC (4 x 2.5 x 2.5cm3), which are displayed in Figures 2a and 2b, respectively. Data were acquired using the HERMES11 sequence (320 a