Auditory magnetic fields in cochlear-implant patients

Neuromagnetic recordings were used to check if electrical stimulation of the auditory nerve in cochlear-implant patients activates cortical auditory areas in a similar manner as acoustic stimulation in normal hearing subjects or whether the excitation processes are different. The waveform of the evoked magnetic field complex elicited by electrical stimulation of the auditory nerve as well as the distribution of the magnetic responses over the head resemble that of auditory-evoked fields elicited by acoustic stimulation of normal subjects. The location and direction of the equivalent dipole are consistent with activation of the auditory cortex. Neuromagnetic recordings could be used in the future (i) to check activation of the auditory cortices in cochlear-implant patients; (ii) to gather information about the functional properties of this activity, and (iii) to study the integrity of central auditory pathways in totally deaf patients.