Intracranial evidence for differential encoding of frequency and duration discrimination responses

Objective: To identify cortical areas involved in auditory detection and discrimination of frequency and duration stimuli in an awake child. Design: Single case study recording intracranial auditory event-related potentials 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 discrimination. Frequency MMN overlapped with the N1 whereas duration MMN appeared 100 msec later. MMN to both duration and frequency appeared as an additive bifid response. Conclusions: It is suggested that feature-specific neuronal networks are activated after changes in sounds, which may underpin a fast parallel preattentive process (MMN).