A method and system are described for, based upon a plurality of previously-acquired directional LFP signals measured in a plurality of different directions at a directional sensor lead located in a predetermined region of a patient's brain, determining optimised patient-specific programming parameters for programming a directional stimulation lead with parameters for stimulating the said region. The method comprises a first step of determining, over at least one predetermined frequency range, a power-frequency variation curve of each of the directional LFP signals, a second step of identifying frequency peaks in the power- frequency variation curves, a third step of detecting one of the identified frequency peaks at which a maximum difference in signal power between the directional LFP signals occurs, and a fourth step of calculating a plurality of directional stimulation weighting factors on the basis of the relative signal powers of the directional LFP signals at the detected frequency peak.