The relationship between brain’s GABA and glutamate/glutamine (Glx) concentrations measured by 1H MRS, hemodynamic response, neural signaling, and behavior is poorly understood. Here, the relationship between MRS-detectable GABA and Glx signals and MR hemodynamic contrasts during visual stimulation were examined. It was observed that changes in GABA+ and Glx were positively correlated with the BOLD response and negatively correlated with their levels at rest. Additionally, task GABA+ concentrations were negatively correlated with cerebral metabolic rate of oxygen (CMRO2). Together, these results suggest shifts in the inhibitory/excitatory balance and metabolism to maintain homeostasis in the brain.