Intracranial evidence for differential encoding of frequency and duration discrimination responses

Objective: To identify cortical areas involved in auditory detection and di scrimination of frequency and duration stimuli in an awake child. Design: Single case study recording intracranial auditory event-related pot entials to auditory oddball stimuli varying in duration and/or frequency. Results: N1 wave to detection was recorded maximally just above the Sylvian fissure 1 cm posterior to the mismatch negativity (MMN) response to discri mination. Frequency MMN overlapped with the N1 whereas duration MMN appeare d 100 msec later. MMN to both duration and frequency appeared as an additiv e bifid response. Conclusions: It is suggested that feature-specific neuronal networks are ac tivated after changes in sounds, which may underpin a fast parallel preatte ntive process (MMN).