P300/MMN Recording

Eclipse Support

The mismatch negativity (MMN) response is a negative wave elicited in an ‘oddball’ paradigm where by a deviant stimuli is presented amongst a stream of repeated, or standard, stimuli. The response can be observed by subtracting the responses to the standard stimuli from those of the deviant, and it occurs in the latency region of around 100-300ms. See Fig1, showing an MMN from a 2 kHz deviant tone burst presented amongst a stream of 1 kHz standard tone bursts, measured between vertex and linked- mastoid positions.

The P300 response is a positive wave that is also usually elicited in an oddball paradigm. Unlike the MMN, which can be measured without any task requirements, the P300 only occurs when the listener is actively attending to the stimuli. See Fig 2, showing a P300 from a 2 kHz deviant tone burst presented amongst a stream of 1 kHz standard tone bursts, measured between vertex and linked- mastoid positions.

The MMN and P300 can be used to evaluate higher level auditory function. The MMN test is particularly related to the brain’s ability to discriminate between speech sounds, and its independence of attention may make is suitable for use in evaluating auditory function in various populations in clinical neuroscience and in infants and newborns (Garrido et al., 2009).

Patient arousal and attention state greatly affects the amplitudes of the MMN response, so it is very important that the patient understands the test procedure. The MMN can also be elicited when the subject pays attention to stimuli, but it is difficult to measure in this condition because of the overlapping N2 component. As a result it is recommended to record the MMN while the subject ignores the stimuli. This can be done by letting the subject read or watch a silent captioned video during recording.

The MMN amplitudes decrease with various stages of sleep. It is not advised to perform MMN under sedation.

It is possible to obtain P300/MMN with a standard 2-channel electrode montage, with an active vertex electrode referenced to either right or left mastoid. However, stronger responses can be obtained by linking the right and left mastoids, recording both from the ipsilateral and contralateral side in order to avoid a bias in hemispheric laterality.

The Eclipse comes with a pre-programmed protocol for P300/MMN testing (license), ready for immediate use. Protocols can be created or modified easily to fit your clinic needs. Consult your Eclipse Additional Information to learn how to create or modify a protocol.

P300/MMN should be measured using toneburst from 250 Hz-4 kHz and custom wave files at an intensity of a moderate levels.