Neuromagnetic Evidence of Functional Organization of the Auditory Cortex in Humans

The influence of two physical stimulus parameters (frequency and intensity) and of one sensation parameter (pitch) on the auditory evoked magnetic field (AEF) was quantified by approximating the measured magnetic field distribution by that of an equivalent current dipole (ECD) embedded in a homogeneous semi-infinite volume conductor. The main results are as follows: The depth of the ECD increases with increasing frequency, but decreases with increasing intensity. In the case of a complex tone with missing fundamental it is the virtual pitch that determines the ECD location and not the spectral contents of the stimulus.