I think the primary difference is that MMN is a mismatch to negative signal and p3 is a positive signal it's more how it is measured than anything else. MMN is measured in relation to the negative side of the brain as a mismatch between signals, and P3 is measured with respect to ground or a common of some sort.

MMN can be obtained in a passive condition, because this difference wave reflects an automatic process. Automatic means here: attention is not necessary to evoke the MMN. In contrast, the P3a has been discussed in context with attention.

http://www.ncbi.nlm.nih.gov/pubmed/17573239

Further, P3a can be easily obtained with a variety of modalities. The MMN has been typically examined in audition, whereas there is also evidence for a visual countepart of the MMN.

http://www.ncbi.nlm.nih.gov/pubmed/21878790

hope this helps

Tobi

Without knowing what types of processing you'd hope to index with ERPs, it's a little challenging to just spew out traits for MMN vs P3a. My understanding is that, as the earlier onset response, MMN can be seen as evidence of the detection of deviance from an auditory template established by recurring sounds. That detection of deviance- a mismatch from a memory of prior stimui- might (or might not) be the precursor level of analysis necessary for an oddball stimulus to be further evaluated for commitment of additional attention (early orienting reflected in P3a). Arguments have been made that MMN's behavior shows reliance on a memory buffer for recent sounds, and thus it may have some use as an index for a type of auditory short-term memory. MMN has also had some interesting reports correlating it with subjective phenomena- oddball trains that elicit awareness of changes have been found to elicit MMN, but when the trains become too similar for confident discrimination, MMN is also diminished. I do not know if an old case study from a few subjects has ever been replicated, but intriguingly, the return of MMN in deep coma patients was a strong harbinger for emergence from coma. My sense is that, for audition at least, MMN reflects the very early detection of novelty that can be subsequently elaborated and reflected in later cognitive ERP components.

Hi,

It is very inmportant to know what you want aspect of auditory processing do you want to look at. MMN is an index of pre-attentive auditory discrimination. The elicitation of MMN needs the formation of a memory trace of a signal a sudden occurence of the stimulus which is a mismatch to the formed memory trace. The P300 on the other hand requires active attentional resources. the subject has to respond or have some assocaition with the target stimulus and give a response or allocate attention to the target stimulus.

If I look at you question you want to record the P3a which is supposed to be a component which generated by relatively automatic processing. This component is generated in the frontal areas compared to P3b. an importannt consideration in recording the P3a is that the target stimulus should be so very different from the standard stimuli and should be able to draw sufficient attention ( this is when uyou are not have the subject actively respond). A name call would be a good target along with a pure tone standards, or in your the case of your rats a cat's "mew" might help. If you want to record the MMN and P300 in the same recording it is going to be difficult because in such cases its very difficult to separate the MMN from the N2a component of the P300. One thing you may possibly try is a faster repetirion ratewhich reduces the P3 amplitude and does not alter the MMN also you can also rule out N1 effect here. another thing would be to use a larger number of stimuli, the P300 reduces with repetitions of the target stimulus but the MMN does not reduce so very much. If intereseted you can read the review about MMN by Risto Naatanen

http://web.mit.edu/carrien/Public/speechlab/papers/naatanen-paavilainen-rinne-alho-2007.pdf

Hope this helps

Cheers

Nike

The MMN reflects violation of temporal regularity and represent automatic sensory discrimination and is a difference between two reactions:

1- response to unexpected deviant (novelty)

2- response to expected standard, which reflect a perceptual learning (induced by standards presentation).

The P3a represents the response to unexpected deviant (novelty) associated with a shift/orientation of the attention.

From this one can deduce that:

a) the MMN reflects also the perceptual learning while P3a does not;

b) P3a reflects attention shift, while the MMN does not.

However, it is possible to have both components in one ERP as the mechanisms are usually cooperating in healthy organism. I agree with Nike, you can modulate the P3a by inter-stimulus interval and different stimulus saliency. You can also modulate MMN by frequency and other odd-ball parameters.

As the P3a is attention related, it is not clear if you will be able to record it under anaesthesia, although there is some evidence that it is possible http://www.ncbi.nlm.nih.gov/pubmed/8457051 in humans. So it would be worth of trying :)

General comment to statement that MMN is a mechanism independent from attention (or preattentional). The process of perceptual can be modulated by attention and therefore it influences also MMN. For nice review by Sussman see: http://www.psycontent.com/content/l5g4m8504r414560/