In vivo 1H NM spectroscopy at 7 T was utilized to measure the changes of lactate concentration upon repeated identical visual stimuli, each lasting 2 min. The amplitude of these changes was attenuated from the initial value of 0.2 μmol/g and gradually disappeared in the noise. In sharp contrast, the Blood Oxygen Level Dependent (BOLD) effect was persistent during the whole paradigm. This finding may suggest a differential adaptation of cortical output that is not reflected at the level of the global excitation-inhibition activity of the cortical canonical circuits.