1. A device for resetting phases of neuronal activity, the device comprising: a control unit; and a plurality of stimulation units electrically coupled to the control unit and configured to be implanted in the body of the patient and to generate optical stimuli to stimulate neurons at a plurality of respective stimulation locations, wherein the optical stimuli reset the phases of the neuronal activity of the neurons during the direct stimulation of the neurons exhibiting abnormally synchronous and oscillatory neuronal activity, wherein the control unit is configured to actuate the stimulation units such that at least two of the plurality of stimulation units reset the phases of the respectively stimulated neurons at different times, wherein the number of stimulation units is N, wherein the j-th stimulation unit applies an optical stimulation signal S j (t)=A j x j (t)θ[x j (t)] to the respective stimulation location, with j=1, 2,. .. , N and x j (t)=sin[ωt+(j−1)2π/N] and θ[x j (t)]=0 for x j (t)≦0 and θ[x j (t)]=1 for x j (t)>0 , and wherein A j is an amplitude and ω is a stimulation frequency.