What is described here is a process and a device for deep-selective detection of spontaneous activities and general muscle activities in biological tissue. In this process, photons of a coherent and monochromatic electromagnetic radiation of the wavelength λ1 penetrate the tissue in the range between 600 and 1,200 nm and re-emerge from the tissue at differently distanced areas, then being detected with regard to frequency and number or intensity. By means of an evaluation program or algorithm, this information in connection with the respective area as point of emergence of the photons allows conclusions to be drawn about the muscle activity and/or number of active muscles and/or the physical position of the active muscles in the tissue. In order to improve the preciseness, it is intended to insert photons into the tissue of at least one further coherent and monochromatic electromagnetic radiation of another wavelength λ2 and to detect them after emergence from the tissue with regard to frequency and number or intensity. The wavelengths λ1 and λ2 are selected in such a way that there will not occur any interference fringes.
