It ultimately has to be experienced, since it's about dropping/representational out of the discursive mode in which we spend most of our waking time (the default mode network in cognitive science). For me it feels like returning to reality after a VR session. Or like exiting a hall of mirrors. Experience gets imbued with a feeling of stableness, stillness, contentment and appreciation of the simple fact of just being. There's a podcast that talks about these things, for example this episode: https://deconstructingyourself.com/dy-014-diving-deep-jhanas... Zen and the Brain is a good book on the connections with neuroscience.
