I've recently become aware about existence of such phenomena. From my naive point of view, I understood it as existence of two general types of neural cells, one type serve inhibitory purpose and the other one provide excitation, all of this happens through variation of concentration of different mediators in synaptic connections, right? So in this process (transmarginal inhibition), in a nutshell, provoked by overwhelming stimuli, layer of cells which inhibit inhibitory cell start to show increase of activity and hence inhibitory cells can no longer control activity of currently "excited" cells which result in "paradoxal", reversed behavior. Sorry for this clumsy explanation of how I understood this, please correct my view. If i can abstractly think about evolution of some particular part of biological system as a function which tries to arrive at "local maximum", what type of arrangement of environmental variables could introduce this kind of structure which suffer from such horrible drawback. I mean, there was some input and desired output (adaptation), in result we got construction which could be shut down be intensive external influence and permanently corrupted.