The present invention proposes a method for calculating, presenting, and combining probabilistic functional maps (PFMs) of the human brain representing the probability of structures existing. The method comprises three major steps: reading of data containing the coordinates of contacts, calculating the PFMs, and presenting the PFMs. The data can be read from a file in text or binary format or from a database as local or remote client. The PFM calculation comprises the following steps: forming 3D models of contacts, normalizing the contact models, voxelizing the contact models, calculating an atlas function, and calculating the PFM. The PFM can be presented alone or along with anatomical atlases. Both 3D and 2D interfaces can be used for presentation. The proposed method also includes different ways of combining the contact data and/or existing PFMs from multiple sources. This mechanism is the basis of an internet portal for stereotactic and functional neurosurgery.