The application relates to a hearing assistance device comprising an implanted part adapted for being implanted at a user's ear. The application further relates to a method of operating a hearing assistance device. The object of the present application is to improve identification and processing of recorded nerve response data in an implanted part of a hearing assistance device. The problem is solved in that the implanted part comprises a) A multitude of electrodes adapted for being located in the cochlea in proximity of an auditory nerve of the user； b) Stimulation circuitry electrically coupled to a stimulation electrode during a stimulation time period and configured for applying a stimulation signal to the stimulation electrode； c) Measurement circuitry electrically coupled to a recording electrode during a measurement time period and configured to measure a signal picked up by the recording electrode in response to said stimulation signal and providing a measured signal； d) A control unit configured to control the timing of the application of the stimulation signal in the stimulation time period and to control the measurement time period relative to the stimulation time period； and e) A processing unit configured to record the measured signal in the measurement time period and to identify a response from the auditory nerve based on said measured signal. This has the advantage of reducing the bandwidth requirement of a communication link to an external part during fitting. The invention may e.g. be used for cochlear implant type hearing aids, in particular during the fitting of such hearing aid to a particular user.
