1. A method for determining stimulation signals in a cortical stimulation apparatus in which an electrode array, having at least one electrode adapted to be implanted in the cortex of a patient, is controlled by a control system, said method including at least the following steps: (a) a measuring step wherein a number n of electric signals is collected by said control system, each at a respective electrode of said electrode array, n being at least 1; (b) a processing step wherein said control system determines n stimulation signals, by a virtual neural field having a virtual array of n points corresponding to each electrode of the electrode array having collected an electric signal at the measuring step, said virtual array receiving the collected signal as an input on each of the n points and said virtual neural field being adapted to control the frequency spectrum of neural activity in the cortex, each stimulation signal being determined by a value of said virtual potential at each point of the virtual array; (c) a stimulation step wherein said stimulation signals are emitted by said control system, respectively at the electrodes of said electrode array corresponding respectively to the points of the virtual array.