If ghosts existed, they'd be everywhere. And if all the stories of how they manifest were true, reports of them would be much more widespread.
But instead, 'ghosts' are generally reported in old draughty buildings or places where people already feel irrational fear. The various 'phenomena' reported in 'ghost sightings' have other explanations, such as imagination, lack of sleep, synaesthesia, hypoxia, mental illness, draughts, structural expansion and contraction, etc, etc.
No nervous system, no ghost.