Frontal GABA levels associate with musical rhythm production in healthy aging adults.

Changes in neuronal inhibition have been implicated in age-related declines in sensorimotor performance. While indirect evidence suggests that inhibitory mechanisms are also involved in rhythm entrainment, this association has not been tested. Using magnetic resonance spectroscopy, we tested the association between dorsomedial frontal GABA+/H2O concentrations and musical rhythm production in healthy younger (n = 14; 18-35) and older (n = 12; 55-79) adults, hypothesizing that lower GABA+/H2O concentrations would be associated with increased timing error, particularly on more difficult exercises, and intra-individual variability (quantified via mean successive squared difference (MSSD)). Rhythm learning exercises were presented in order of complexity. Linear mixed effects modeling revealed GABA+/H2O-by-exercise number interaction (β = -0.59, p = 0.006) such that participants with lower GABA+/H2O showed greater performance decrement with increasing exercise difficulty. GABA+/H2O trended toward an inverse association with MSSD (β = -0.25, p = 0.089), such that higher GABA+/H2O was associated with lower variability in performance. Older age was associated with increased absolute timing error (β = 0.66, p < 0.001) and greater MSSD (β = 0.86, p = 0.012). However, there was no evidence for age group differences in GABA+/H2O-performance relationships. This finding suggests that GABAergic neuronal inhibition may be important in musical rhythm production across age groups.