Neuromagnetic responses of the human auditory cortex to short frequency glides.

Neuromagnetic responses were recorded to 33-ms frequency-glide tones with a 7-channel SQUID gradiometer. Ninety per cent of the tones were of rising/falling frequency and 10% otherwise similar tones but presented backwards, i.e. comparable falling/rising frequency glides. The infrequent stimuli elicited a specific response, the mismatch field (MMF), whose equivalent source suggested a generation in the supratemporal auditory cortex. Responses to rising and falling infrequent glides showed no consistent asymmetry. The MMF amplitude correlated positively with the glide magnitude. It is suggested that the generation of MMF to changes in the direction of frequency glides involves neuronal networks tuned to frequency glides.