RAPID ONLINE ESTIMATION OF RESPONSES TO TRANSCRANIAL MAGNETIC AND PERIPHERAL-NERVE ELECTRICAL-STIMULATION IN SINGLE HUMAN MOTONEURONS

Cross-correlation experiments allow to obtain information about synapt ic potentials in human motoneurons. However, recording cross-correlati on responses of one motoneuron to transcranial magnetic and electrical peripheral nerve stimulation requires a considerable recording time w hen both responses are recorded consecutively. In this paper a method is introduced yielding the same information about the responses of a s ingle motoneuron to both types of stimuli while requiring only a fract ion of the recording time necessary for a conventional cross-correlati on experiment. The main features of the method introduced were: (i) us e of the recharging time of the magnetic stimulator for response recor ding to the electrical stimulus, (ii) use of specific stimulus timing with respect to the motor unit discharges, and (iii) on-line display w ith statistical testing of the response functions allowing to stop sti mulus application, if the responses to both types of stimuli had reach ed statistical significance. Application of the method is demonstrated with reponse recording of 70 tibialis anterior motor units from five healthy volunteers to transcranial magnetic and peroneal nerve electri cal stimulation.