"Beyond Good and Evil: The Time-Course of Neural Activity Elicited by Specific Picture Content"
Event related potentials and negative bias: ERPs were time-locked to the stimulus onset, in this case, subjects were shown pictures sorted into the categories as shown in the figure above. Researchers measured the late positive potential or the LPP, which is understood to reflect motivated attention.
Overall, and as expected, unpleasant images elicited a larger response than neutral or pleasant images, specifically images of erotica and mutilation were compatible in LLPs, as were affiliative and threatening images - as you can see.
No mention of mirror neuron activity, which would be interesting to look at.