Silica pathways
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Not much is known about what silica pathways are, but Commander Adama compares them to a brain of sorts for Cylons when he confronts Leoben Conoy in the bowels of Ragnar Anchorage in the Mini-Series.
"What you've got is Silica pathways to the brain. Or whatever it is you call that thing you pretend to think with. It's decomposing as we speak." -- Commander Adama, Mini-Series