NLA Action of material Mix Shader node FAC value

Question

I'm creating an animation where regions of the brain light up and turn off, cued to video and sound. Many many keyframes of essentially "fade on / fade off" switches for each of the 6 highlighted regions.

I started keyframing the Mix Shader node FAC values using a transparent shader to "turn off" the highlight, but there are too many keyframes to do and it's getting out of hand.

This feels similar to NLA actions - drop "cerebellum on" action strips where I want to turn "on" the cerebellum; and more easily adjust timing and add transitions to suit video...

...but I'm not able to create an action strip of a material! Is this possible? Is there a trick to do it?

I then thought of using an empty's x location to drive the FAC value of the mix node in the material and create action strips of the empty, but don't know how... does this require a Python script?

Is this something the fabled animation nodes could help resolve?

Answer 1

Found the answer: Fade in action applicable to all objects (in cycles)

Keyframe the object's pass index from 0 to 100, use the object info node:object index output, connect to math(multiply) node with value of .01, connect to FAC value input on mix node.The object's pass index gets recorded in the NLA editor, so I have my action strip!