Neurofeedback is a form of biofeedback that uses electrical potentials in the brain to reinforce desired brain states through operant conditioning. This process is non-invasive neurotherapy and typically collects brain activity data using electroencephalography (EEG). Several neurofeedback protocols exist, with potential additional benefit from use of quantitative electroencephalography (QEEG) or functional magnetic resonance imaging (fMRI) to localize and personalize treatment. Related technologies include functional near-infrared spectroscopy-mediated (fNIRS) neurofeedback, hemoencephalography biofeedback (HEG), and fMRI biofeedback. Placebo-controlled trials have often found the control group to show the same level of improvement as the group receiving actual neurofeedback treatment, which suggests these improvements may be caused by secondary effects instead. Neurofeedback has been shown to trigger positive behavioral outcomes, such as relieving symptoms related to psychiatric disorders or improving specific cognitive functions in healthy participants. These positive behavioral outcomes rely on brain plasticity mechanisms and the ability of subjects to learn throughout life.