The electrical activity of our brain is rhythmic and, when measured by EEG (electroencephalography), presents itself as "brain waves" of different frequencies. Both internal processes (e.g. concentration, relaxation, falling asleep...) and external stimuli can influence brain activity. For example, when we listen to music with a slow rhythm, our brain waves slow down; the opposite happens with music in a fast rhythm. It is also known that flashing lights can influence brain waves. When a light flashes steadily into the eye, the brain is stimulated, causing brainwaves to be brought to the same frequency as the flashing light by regulating brain centres (so-called entrainment or photic driving). When the light flashes faster, the brain frequency increases, whereas when the light flashes slower, the brain activity slows down. Neurotherapists benefit from this natural phenomenon because of its potential to alter brain wave amplitudes and patterns and thus the functional states of the brain. Audio-visual entrainment (AVE) refers to the use of flashing lights and rhythmic sounds to target brainwaves towards a desired rhythm or specific EEG frequencies. By stimulating the brain with flashing lights through special glasses and pulsating sounds through headphones, it is possible to temporarily shift the frequency of dominant brain waves in a desired direction for the duration of the stimulation, thereby altering brain function.