Analysis and modeling of the mechanism for generating auditory-evoked fields

Neuromagnetic signals in response to each of repetitive tone-bursts were analyzed in the frequency and time domains. Firstly, ongoing oscillations between 3 and 16 Hz were relevant to the generation of auditory-evoked fields. Secondly, their phases were locked at around the timings of N100m but not locked at the other timings. Thirdly, amplitudes of the oscillations were larger, on average, at around the timings of N100m than at the other timings. Fourthly, spatial distributions of the oscillations were often reduced to an equivalent current dipole in the auditory cortex at around the timings of N100m but seldom reduced at the other timings. A model with several oscillators within the auditory cortex was proposed: their phases were locked at around the timings of N100m but asynchronous at the other timings. Simulations validated this model.