Quick Guide – P300/MMN recording What is a P300/MMN? The mismatch negativity (MMN) response is a negative wave elicited by a combination of standard and deviant stimuli. The response occurs in the latency region of around 100-300ms. See picture (Hall, 2007). Why P300/MMN? P300 and MMN can be used to evaluate higher level auditory function. The MMN test is particular related to the brain’s ability to discriminate between speech sounds. P300/MMN is elicited with an oddball paradigm in which infrequent occurring deviant sounds are embedded in a series of frequently occurring standard sounds. The duration of P300/MMN stimuli are much longer compared to traditional ABR stimuli. How to test Patient Preparation is very important. 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 N21 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 P300/MMN under sedation. Electrode Placement: It is possible to obtain P300/MMN with a standard ABR electrode montage, however stronger responses can be obtained by linking the Right and Left ear, recording both from the ipsilateral and contralateral side. RED Right mastoid or ear lobe (reference or inverting) BLUE Left mastoid or earlobe (reference or inverting) It is advised to jumper Red and Blue electrode to establish an averaged reference. Item No. 8106696 WHITE True CZ (active or non-inverting) BLACK Ground at cheek or low forehead - distance of few cm to WHITE electrode must be observed. Page 1 of 2 Setting up the Eclipse 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. Protocol settings P300/MMN should be measured using toneburst from 250Hz-4kHz and custom wave files at an intensity of a moderate levels. Amplitudes are larger for binaural than monaural stimuli. Custom wavefiles inclusing Da, Ba and Ga are placed on the EPx5 CD-ROM. Please refer to the chapter Importing wavefiles for stimuli in Instruction for Use for guidelines on importing and calibrating custom wavefiles. Summary of parameters for P300 and MMN Subject Stimuli P1, N1, P2 supra threshold P300 MMN State Awake and quit adults, children and infants Awake and quit adults, children and infants Eyes Eyes open Eyes open Condition Attend or ignore conditions Ignore conditions Types of stimuli Tone burst, speech vowels or consonant vowel combinations Tone burst, speech vowels or consonant vowel combinations Inter-onset interval 1-2 sec 0.1-1 sec Stimulus duration 50-300ms Be careful of overlapping response if analysis time is short Presentation Oddball paradigm Deviant probability 0.05-0.20 Number of deviants at least 200 Intensity 60-80dB peSPL 60-80dB peSPL Reference electrode Tip of nose of averaged reference (jumped electrodes) Tip of nose of averaged reference (jumped electrodes) Filtering 1-30Hz 1-30Hz Analysis time Pre stimuli -100ms Post stimuli 700ms or more Pre stimuli -50ms or more Post stimuli 400ms or more sweep 50-300 50-300 replications At least 2 At least 2, resulting in at least 200 deviants. Measurements Adult Children Infants Measures P1, N1, P2 P1, N200-250 Reliable components Baseline to peak amplitude, peak latency Use latency window established using grand mean data Any age, use difference waveform (response to deviant) Baseline to peak amplitude, peak latency Consider mean MMN amplitude in response window Use latency window established using grand mean data Response presence Determined by Replicable components Response 2-3 times larger than amplitude in pre-stimulus interval Replicable components Response 2-3 times larger than amplitude in pre-stimulus interval Recordings References Hall, J.W. (2007). New Handbook of Auditory Evoked Responses. Pearson Item No. 8106696 Page 2 of 2
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