Adaptation of neuromagnetic N1 without shifts in dipolar orientation

306-channel magnetoencephalography, coregistered with high-resolution volumetric magnetic resonance imaging, was used with 10 healthy participants to test if repetition adapts subsequent processing of sounds in a sequence and whether this adaptation influenced the orientation of the dipolar sources in the auditory cortex. Auditory N1m responses to 1 kHz pure tones were indexed by clusters of sensors situated bilaterally over the temporal lobes. N1m was augmented in amplitude at an interstimulus interval of 16 s relative to 1 s. This neuromagnetic amplitude augment occurred in dipoles in the vicinity of the auditory cortex, without significant shifts in the dipolar orientation. Recent repetition thus adapts auditory cortical neurons, in a manner subject to recovery after a period of silence.