There are disclosed methods and apparatus for determining electrical properties in a peripheral nerve of a human or animal subject. A plurality of electrodes are spaced around a perimeter of the peripheral nerve, and a phase separated pair of first and second probe electrical signals are applied simultaneously to a set of respective first and second combinations of electrodes, the phase separated pair of first and second probe electrical signals having different signal phases from each other. One or more combined responses to the phase separated pair are collected at one or more of the plurality of electrodes, and a pair of phase separated electrical responses are collected corresponding to the different signal phases from the one or more combined responses. The pair of phase separated electrical responses are used to determine electrical properties of the peripheral nerve within the perimeter.
