Some experience what they call derealization. I think it is a bit of confusion from too much stimuli or too many thoughts in the mind. Learning to focus on one issue at a time can help. It also helps to write down the other thoughts so you can let go of them.

I compare it to juggling. We get too many balls in the air and get caught just trying to keep them in the air and can't focus on any individual ball.

Prior to PCS, we may have had not trouble juggling that same number of balls so we have habits of performance that are tough to maintain with PCS.