QUESTION: After reading your site I have a couple of interrelated questions to pose, With yoga nidra is it possible to select unpleasant samskaras to eliminate rather than any samskara? and how do I witness a specific pre-chosen samskara without accessing pictures / voices / my internal voice?
PARTIAL RESPONSE: If you call up a picture on the monitor of your computer, you can look at the picture. You can open a sound file and listen to it through the speakers. But how would you look at the photo or listen to the sound on the hard drive itself, without a mircroprocessor and without a monitor or speakers? Can you see and hear the bits and bytes of binary language on the hard drive? Similarly, impressions at the causal level, the plane of samskaras, are formless. You are stuck with that confusion. Meditation and contemplation will eventually reveal this to you. Yoga nidra is a method of accessing the causal, formless level. Keep reading the articles and doing the practices and insights will come.
http://www.swamij.com/yoga-nidra.htm