Method and apparatus for probe localization in brain matter. A method is disclosed for determining the insertion point for an object at a desired location within tissue of varying types. The parameters of tissue are first measured at an entry point into the tissue from exterior thereof. The parameters of the tissue are then measured periodically along a line extending from the entry point and moving away therefrom. A determination is then made if at least one boundary between tissue types has occurred during the measurement process. The measurements along the line are then compared to a predetermined map of the tissue boundaries. Thereafter, a point on the map is then selected corresponding to the desired location within the tissue when the measured parameters indicate that the measurements are taking place in proximity thereto.