Cover legend: Measures of cortical physiology and brain metabolism show that the brain state during vigorous physical activity is distinctly different from that seen during sedentary behavior. Among the brain changes during physical exercise in human volunteers is an acute increase in the cortical content of glutamate and GABA. Understanding the brain state during physical activity may provide insights into the neurotherapeutic potentials of exercise. For more information, see the article by Maddock et al. (pages 2449–2457).