We know that, for plosives, when the voice onset time is before the closure event, the consonant is voiced, like [b]; if about the same time, it is tenuis, like [p]; if after, it is aspirated, like [pʰ]. Clearly, the aspirated-tenuis distinction for plosives and affricates exists in many languages. Wikipedia says aspirated-tenuis distinction for fricatives also exists in some languages.
But how about nasals? We know that [mʰ] is possible, and there are languages, like Burmese, that has distinction on [m] and [mʰ]. But what is the tenuis [m]? Can it be that the tenuis is actually [j̃m] (nasal approximant preceding [m]) or [mp] (prenasalized plosive)? If not, what is it? Do some languages have aspirated-tenuis nasal distinction? Or if it does not exist, what is the biological restriction on it?