An electrode array for insertion into soft tissue comprises a multitude of thin flexible electrodes each having a distal tip and a proximal end, wherein at least portions of the electrodes extending from their proximal ends are disposed in parallel. The electrodes are embedded in a matrix dissolvable in an aqueous solvent such as a body fluid. The matrix comprises two or more sections differing in their dissolution rates. A first section encloses a portion of the electrodes extending in a proximal direction from a distal portion thereof. A second section encloses a portion of the electrodes extending from the first section towards their proximal ends.